This document reports on a study of the local density of states of epitaxial antimony nanostructures on silicon 001 using scanning tunneling spectroscopy. The key findings are:
1) Epitaxial antimony lines self-assemble on the silicon surface when antimony is deposited at low rates and the sample is annealed. The lines are two atoms wide and extend up to 12 antimony dimers in length.
2) Spectroscopy shows the electronic structure in the center of the antimony lines is similar to the silicon surface, indicating the lines are nonmetallic. In contrast, the ends of the lines show a finite density of states at the Fermi level, consistent with theoretical predictions of a "radical
1. The document investigates the structural, electronic, and magnetic properties of gadolinium-implanted zinc oxide single crystals through techniques like Rutherford backscattering spectrometry, Raman spectroscopy, and SQUID magnetometry.
2. RBS and channeling measurements show that around 60% of implanted Gd atoms occupy zinc substitutional lattice sites in the ZnO crystal.
3. Ferromagnetic ordering is observed at room temperature in low fluence Gd-implanted and annealed ZnO samples, but decreases at higher implantation fluences, possibly due to antiferromagnetic interactions between Gd atoms.
This document describes the preparation and analysis of mesoporous microspheres of nickel oxide (NiO) for use as a pseudocapacitor material. Mesoporous α-Ni(OH)2 microspheres were first synthesized via a hydrothermal method, then calcined at different temperatures between 250-500°C to produce NiO microspheres. The 250°C NiO sample exhibited the highest specific surface area of 295 m2/g and highest specific capacitance of 1,140 F/g. Characterization of the materials showed the pseudocapacitive behavior was more evident for NiO prepared at higher calcination temperatures. The high surface area and mesoporous structure of the 250°C
High crystalline quality ZnBeSe grown by molecular beam epitaxy with Be}Zn co...Oleg Maksimov
This summary provides the key details from the document in 3 sentences:
The document discusses the growth of high crystalline quality ZnBeSe layers on GaAs substrates using molecular beam epitaxy. It finds that using Be-Zn co-irradiation of the GaAs surface before growing a ZnSe buffer layer or using a BeTe buffer layer improves the crystalline quality of the ZnBeSe layers, resulting in narrower X-ray linewidth and lower etch pit density. Near lattice-matched ZnBeSe layers grown with Be-Zn co-irradiation exhibited an X-ray linewidth as low as 23 arcseconds and a photoluminescence linewidth of about 2.5 meV at 13K.
Oxide film growth on copper in neutral aqueous solutionsAlexander Decker
This document summarizes research on the growth of oxide films on copper in neutral aqueous solutions containing various anions. The key findings are:
1) Copper electrode potentials measured over time in solutions containing aggressive (SO42-, Cl-, Br-, I-) and inhibitive (CrO42-, CO32-, NO2-) anions increased, indicating oxide film growth on the copper surface.
2) The thickness of the copper oxide film reached a maximum at low and high concentrations of the aggressive and inhibitive anions, respectively.
3) The rate of oxide film thickening followed the relationship E = a + b log t, where a and b are constants.
4) The concentration of inhib
http://www.surfacetreatments.it/thinfilms
Literature Review of Nb Electroplating (Dmytro Chirkov - 20')
Speaker: Dmytro Chirkov - Legnaro National Laboratories of INFN | Duration: 20 min.
Abstract
The main aim of this work is try to understand if expensive techniques of niobium coating could be replaced by cheaper electroplating method.
Nowadays electrochemical surface treatment is one of the most used approaches in industry.
Aqueous solutions has been the most widely used process mainly because of advantages such us low cost, non-flammability, high solubility of electrolytes, high conductivities resulting in low ohmic losses, high solubility of metal salts and high rates of mass transfer. However, despite these advantages there are several limitations in using aqueous solutions such as limited potential windows, gas evolution processes that can result in hydrogen embrittlement, passivation of substrates, electrodes and deposits, and the necessity for hazardous complex agents such as cyanide, causing environmental contamination. These are the reasons why new non-aqueous solutions to electrodeposit niobium have been researched.
One of the main limitations in using aqueous solutions is their narrow electrochemical window. The major reason for carrying out electrodeposition in non-aqueous electrolytes (such as conventional organic solvents, ionic liquids and molten salts) is water and air stability and the wide electrochemical window of these media.
Alternatively, also high temperature molten salts have been used extensively for niobium electrodeposition. They have wide potential windows, high conductivities and high solubility for metal salts. In fact, they have most of the advantages of aqueous solutions and overcome most of the limitations of aqueous solutions, but their one major limitation is the very high temperature (more than 750 °C).
Therefore, the alternative to high temperature molten salts was an ionic substance that melts at a low temperature. Over the last few decades, room temperature ionic liquids have been widely studied in various scientific fields due to their interesting properties, such as negligible vapour pressures, high chemical and thermal stability, acceptable intrinsic ionic conductivity and wide potential window.
Ionic liquids are molten salts with melting points below 100 °C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties.
The aim of this work will be the analysis of available literature data in order to have precise knowledge about niobium behavior in the different electrolytes and to get new information about possible electrolytes based on ionic liquids.
Seminar: Fabrication and Characteristics of CMOSJay Baxi
This document summarizes the fabrication and characteristics of CMOS transistors. It describes the structure of nMOS and pMOS transistors including the metal gate, oxide insulator, and doped silicon substrate. It shows the energy band diagrams of nMOS and pMOS transistors in accumulation, depletion, and inversion modes and how applied gate voltages change the band bending. The linear and saturation regions of the nMOS I-V characteristics are explained based on channel charge and carrier velocity. Key capacitances like gate capacitance and diffusion capacitance are also summarized. RC delay models are introduced to estimate inverter delay times.
The document reports on an experiment measuring the interstitial iron concentration in multicrystalline silicon wafers using photoconductance and photoluminescence techniques. Samples underwent chemical treatment and passivation but yielded unexpectedly low minority carrier lifetimes (<20 μs) preventing analysis. Possible reasons for this include contamination during passivation from an unclean substrate holder or imperfections introduced during chemical treatment. Further experiments with a cleaned chamber could provide different results.
Design of a Cathodic Protection System for Corrosion Prevention of a Pipeline...Onyedikachi Martins
This document discusses a student project to design and install a cathodic protection system on coated steel, similar to what is used on parts of a dredger. The student installed a sacrificial zinc anode alongside the steel to act as a galvanic anode and protect the steel from corrosion. The cathodic protection system was then monitored and the potential readings were within the standard protected range, demonstrating that the steel was effectively protected from corrosion by this method. In summary, the student designed and tested a basic galvanic cathodic protection system using a zinc anode to prevent corrosion of coated steel.
1. The document investigates the structural, electronic, and magnetic properties of gadolinium-implanted zinc oxide single crystals through techniques like Rutherford backscattering spectrometry, Raman spectroscopy, and SQUID magnetometry.
2. RBS and channeling measurements show that around 60% of implanted Gd atoms occupy zinc substitutional lattice sites in the ZnO crystal.
3. Ferromagnetic ordering is observed at room temperature in low fluence Gd-implanted and annealed ZnO samples, but decreases at higher implantation fluences, possibly due to antiferromagnetic interactions between Gd atoms.
This document describes the preparation and analysis of mesoporous microspheres of nickel oxide (NiO) for use as a pseudocapacitor material. Mesoporous α-Ni(OH)2 microspheres were first synthesized via a hydrothermal method, then calcined at different temperatures between 250-500°C to produce NiO microspheres. The 250°C NiO sample exhibited the highest specific surface area of 295 m2/g and highest specific capacitance of 1,140 F/g. Characterization of the materials showed the pseudocapacitive behavior was more evident for NiO prepared at higher calcination temperatures. The high surface area and mesoporous structure of the 250°C
High crystalline quality ZnBeSe grown by molecular beam epitaxy with Be}Zn co...Oleg Maksimov
This summary provides the key details from the document in 3 sentences:
The document discusses the growth of high crystalline quality ZnBeSe layers on GaAs substrates using molecular beam epitaxy. It finds that using Be-Zn co-irradiation of the GaAs surface before growing a ZnSe buffer layer or using a BeTe buffer layer improves the crystalline quality of the ZnBeSe layers, resulting in narrower X-ray linewidth and lower etch pit density. Near lattice-matched ZnBeSe layers grown with Be-Zn co-irradiation exhibited an X-ray linewidth as low as 23 arcseconds and a photoluminescence linewidth of about 2.5 meV at 13K.
Oxide film growth on copper in neutral aqueous solutionsAlexander Decker
This document summarizes research on the growth of oxide films on copper in neutral aqueous solutions containing various anions. The key findings are:
1) Copper electrode potentials measured over time in solutions containing aggressive (SO42-, Cl-, Br-, I-) and inhibitive (CrO42-, CO32-, NO2-) anions increased, indicating oxide film growth on the copper surface.
2) The thickness of the copper oxide film reached a maximum at low and high concentrations of the aggressive and inhibitive anions, respectively.
3) The rate of oxide film thickening followed the relationship E = a + b log t, where a and b are constants.
4) The concentration of inhib
http://www.surfacetreatments.it/thinfilms
Literature Review of Nb Electroplating (Dmytro Chirkov - 20')
Speaker: Dmytro Chirkov - Legnaro National Laboratories of INFN | Duration: 20 min.
Abstract
The main aim of this work is try to understand if expensive techniques of niobium coating could be replaced by cheaper electroplating method.
Nowadays electrochemical surface treatment is one of the most used approaches in industry.
Aqueous solutions has been the most widely used process mainly because of advantages such us low cost, non-flammability, high solubility of electrolytes, high conductivities resulting in low ohmic losses, high solubility of metal salts and high rates of mass transfer. However, despite these advantages there are several limitations in using aqueous solutions such as limited potential windows, gas evolution processes that can result in hydrogen embrittlement, passivation of substrates, electrodes and deposits, and the necessity for hazardous complex agents such as cyanide, causing environmental contamination. These are the reasons why new non-aqueous solutions to electrodeposit niobium have been researched.
One of the main limitations in using aqueous solutions is their narrow electrochemical window. The major reason for carrying out electrodeposition in non-aqueous electrolytes (such as conventional organic solvents, ionic liquids and molten salts) is water and air stability and the wide electrochemical window of these media.
Alternatively, also high temperature molten salts have been used extensively for niobium electrodeposition. They have wide potential windows, high conductivities and high solubility for metal salts. In fact, they have most of the advantages of aqueous solutions and overcome most of the limitations of aqueous solutions, but their one major limitation is the very high temperature (more than 750 °C).
Therefore, the alternative to high temperature molten salts was an ionic substance that melts at a low temperature. Over the last few decades, room temperature ionic liquids have been widely studied in various scientific fields due to their interesting properties, such as negligible vapour pressures, high chemical and thermal stability, acceptable intrinsic ionic conductivity and wide potential window.
Ionic liquids are molten salts with melting points below 100 °C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties.
The aim of this work will be the analysis of available literature data in order to have precise knowledge about niobium behavior in the different electrolytes and to get new information about possible electrolytes based on ionic liquids.
Seminar: Fabrication and Characteristics of CMOSJay Baxi
This document summarizes the fabrication and characteristics of CMOS transistors. It describes the structure of nMOS and pMOS transistors including the metal gate, oxide insulator, and doped silicon substrate. It shows the energy band diagrams of nMOS and pMOS transistors in accumulation, depletion, and inversion modes and how applied gate voltages change the band bending. The linear and saturation regions of the nMOS I-V characteristics are explained based on channel charge and carrier velocity. Key capacitances like gate capacitance and diffusion capacitance are also summarized. RC delay models are introduced to estimate inverter delay times.
The document reports on an experiment measuring the interstitial iron concentration in multicrystalline silicon wafers using photoconductance and photoluminescence techniques. Samples underwent chemical treatment and passivation but yielded unexpectedly low minority carrier lifetimes (<20 μs) preventing analysis. Possible reasons for this include contamination during passivation from an unclean substrate holder or imperfections introduced during chemical treatment. Further experiments with a cleaned chamber could provide different results.
Design of a Cathodic Protection System for Corrosion Prevention of a Pipeline...Onyedikachi Martins
This document discusses a student project to design and install a cathodic protection system on coated steel, similar to what is used on parts of a dredger. The student installed a sacrificial zinc anode alongside the steel to act as a galvanic anode and protect the steel from corrosion. The cathodic protection system was then monitored and the potential readings were within the standard protected range, demonstrating that the steel was effectively protected from corrosion by this method. In summary, the student designed and tested a basic galvanic cathodic protection system using a zinc anode to prevent corrosion of coated steel.
The document summarizes a study that characterized the corrosion of a nickel-aluminum (Ni-Al) composite coating compared to a pure nickel coating after 72 hours of immersion in 2M NaCl solution. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used, and scanning electron microscopy was used to examine the corrosion product layers. Results showed the Ni-Al composite had a porous, cracked corrosion product layer that decreased corrosion potential and increased corrosion currents compared to the more protective layer formed on pure nickel. Thus, the Ni-Al composite exhibited lower corrosion resistance than pure nickel in the higher chloride concentration solution.
This document describes the fabrication and electrochemical characterization of carbon nanowalls grown on polycrystalline diamond (CNWs-on-diamond) electrodes. CNWs-on-diamond electrodes were synthesized by DC-PECVD and showed lower background current and larger potential window than CNWs-on-silicon electrodes in cyclic voltammetry measurements. SEM and Raman spectroscopy confirmed the growth of carbon nanowalls on the diamond substrate. The CNWs-on-diamond hybrid structure demonstrates potential for use as an electrode in electrochemical applications and biosensors due to the combined properties of diamond and carbon nanowalls.
This document summarizes research on using electrodeposited manganese dioxide (MnO2) coatings on porous carbon substrates for capacitive deionization (CDI) applications. Two carbon substrates with different surface areas and morphologies were coated with MnO2 using galvanostatic and cyclic voltammetric deposition. Characterization of the coated electrodes found mixed MnO2 phases present. Testing in half-cell configurations showed that maximum ion uptake per mass was not necessarily optimal for practical CDI applications, where performance per electrode area is more important. The results suggest the structure and deposition method can impact how effectively the electrode volume participates in ion removal reactions.
Growth of GaN films on GaAs substrates in an As-free environmentOleg Maksimov
Direct growth of GaN on GaAs substrates in an As-free environment results in a polycrystalline film with misoriented grains and inclusions. Adopting a procedure of substrate nitridation, deposition of a low-temperature GaN buffer layer, and high-temperature overgrowth significantly improves film quality. The improved films have better crystallinity, fewer defects, and a smoother surface morphology. Transmission electron microscopy analysis reveals the films have a columnar structure with straight grain boundaries and defects concentrated at the interface with the GaAs substrate.
“Kinetics and mechanism of sulphuric acid oxidation of glycolic (ga) by selen...آفتاب حسین
This document provides an introduction to a study on the kinetics and mechanism of the oxidation of glycolic acid by selenium dioxide in an aqueous-acid medium. It discusses background information on chemical kinetics, oxidation-reduction reactions, and selenium dioxide as an oxidizing agent. Previous studies on the oxidation of various compounds like ketones using selenium dioxide are also summarized. The document lays out context for investigating the reaction kinetics and mechanism of glycolic acid oxidation.
Anne marie valente feliciano - nucleation of nb films on cu substratesthinfilmsworkshop
In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. All these along with the quality of the Cu substrate have an important influence on the nucleation and subsequent growth of the Nb film, creating a favorable template for growing the final surface exposed to SRF fields. This contribution shows how the structure and defect density thus electron mean free path (represented by residual resistance ratio values) of Nb films can be tailored on Cu substrates, by varying the ion energy and thermal energy provided to the substrate, favoring the hetero-epitaxial or the fiber growth mode.
This document discusses cathodic protection techniques for marine applications. It covers the use of cathodic protection on marine pipelines, offshore structures, and ship hulls. For marine pipelines, coatings are used along with supplemental cathodic protection using sacrificial anodes to protect areas where the coating is damaged. Offshore structures are protected through sacrificial anode systems or hybrid designs using impressed current along with sacrificial anodes. Ship hulls also use coatings along with cathodic protection systems using zinc anodes or impressed current systems on large ships to polarize the structure.
Silicon carbide (SiC) is a wide bandgap semiconductor material useful for high temperature, high power, and high frequency applications. It has exceptional properties like high thermal conductivity, hardness, and electric field breakdown strength. There are over 200 known polytypes of SiC crystal structures defined by their stacking sequences. Common polytypes include 3C, 2H, 4H, 6H and 15R SiC. 4H-SiC has better electrical properties than other polytypes making it suitable for power devices. SiC can be doped n-type or p-type and exhibits high electron and hole mobilities. It is widely used for applications requiring operation at high temperatures and voltages.
This document discusses oxidation in semiconductor device fabrication. It describes oxidation as the process of converting silicon into silicon dioxide, which can occur through dry oxidation using oxygen or wet oxidation using water/steam at high temperatures from 900-1200°C. The key functions of the resulting silicon dioxide layer include acting as a diffusion mask, providing surface passivation and insulation, and enabling device isolation in integrated circuits. The document also classifies oxidation as either diffusion limited or reaction controlled depending on oxide thickness and oxidation time.
Galvanic anodes provide cathodic protection to buried metallic structures using sacrificial anodes made of materials more electronegative than the structure, like magnesium or zinc alloys. The anode material corrodes to provide a protective current without an external power source. Selection involves analyzing performance, cost, and calculating requirements like anode size based on structure size, material properties, design life, and protection criteria. Installation and maintenance costs are generally low for galvanic systems.
This document discusses cathodic protection, which involves applying a small electric current to the surface of a metal structure to prevent corrosion. It describes two main methods: impressed current uses an external power source connected between the structure and an auxiliary anode buried in the ground, while sacrificial anodes rely on galvanic action between the structure and more reactive anodes. The principles of cathodic protection involve driving the structure's potential negative of its corrosion potential to inhibit the corrosion reaction while increasing the cathodic reaction. Proper design considers factors like protection potentials, current density, coatings, and avoiding over-protection.
Phillips - Atomic Layer Deposition of NbN Thin Films for Superconducting Radi...thinfilmsworkshop
http://www.surfacetreatments.it/thinfilms
Atomic Layer Deposition of NbN thin films for SRF applications (Larry Phillips - 15')
Speaker: Larry Phillips - Jefferson Lab - Newport News - Virginia | Duration: 15 min.
Abstract
Niobium Nitride is a 17K superconductor investigated since early eighthies for Superconducting Radiofrequency applications.
Atomic Layer deposition is instead a technique that only recently starts to be considered for industrial applications.
Electrical Properties of Reservoir RocksShah Naseer
The document discusses electrical properties of reservoir rocks and methods for determining fluid saturations. It explains that electrical resistivity is a measure of how much electrical current can flow through a material and is affected by porosity, pore fluid type and saturation, and lithology. Common methods to determine fluid saturations include well log analysis, core analysis, and capillary pressure measurements. Resistivity is highest for gas, intermediate for oil, and lowest for water-saturated rocks. Resistivity decreases as water saturation increases. Equations are presented relating true resistivity to water resistivity, porosity, and water saturation.
THE UTILISATION OF 2-D RESISTIVITY AND INDUCED POLARIZATION (IP) METHODKasdi Nata Sujono
The document summarizes a study that used 2-D resistivity and induced polarization (IP) methods to determine iron ore bodies at Kampung Melaka, Kuala Lipis, Pahang, Malaysia. Three survey lines totaling 600 meters were divided into lots of 200 meters each. The 2-D resistivity method identified iron ore by its low resistivity, while IP differentiated iron ore and groundwater. Results showed iron ore underlying the surface from 5-30 meters was mostly located in lots 1 and 2 based on their low resistivity. Lot 1 contained 20-25% iron ore, lot 2 contained 30-35% iron ore, and lot 3 contained 15-20% iron ore over each 200-meter
Temperature Dependence of the Band-Edge Transitions of ZnCdBeSeOleg Maksimov
This study characterized the temperature dependence of band-edge transitions in three ZnCdBeSe films with varying concentrations of beryllium (Be) using contactless electroreflectance (CER) and piezoreflectance (PzR) measurements from 15-450K. The CER and PzR spectra showed doublet features near the band edge, indicating light-hole and heavy-hole excitonic transitions. Comparing the relative intensities of the PzR and CER spectra allowed identification of the transitions. Analysis of the temperature dependence provided information on how the energy and broadening of the transitions varied with temperature and Be concentration. The results showed that incorporating Be effectively reduced the rate of temperature variation of the energy
The document reviews silicon carbide (SiC) based power semiconductor devices and their applications. It discusses how the superior material properties of SiC, such as its wide bandgap, high electric field, and high thermal conductivity, allow it to handle higher power ratings, switching frequencies, and operating temperatures compared to silicon-based devices. The document provides an overview of the available SiC power devices, including diodes and MOSFETs, and compares the theoretical advantages of SiC devices to silicon, such as their thinner depletion widths, lower on-state resistances, and higher breakdown voltages. It also briefly discusses potential converter topologies that can benefit from using SiC semiconductor devices.
1. Electron irradiation of sapphire (Al2O3) results in both electronic and nuclear damage.
2. Electronic damage includes electron excitation and ionization via interactions between the incident 1 MeV electrons and the aluminum and oxygen atoms in Al2O3.
3. Nuclear damage, or displacement damage, occurs when electrons transfer sufficient energy to atomic nuclei to displace them from their lattice sites, calculated using models of electron-atom cross sections and displacement thresholds.
1999 observation of zero creep in piezoelectric actuatorspmloscholte
The document summarizes experiments on piezoelectric actuators that observe zero creep in certain locations of the hysteresis loop. Specifically:
1) Relaxation experiments using an offset sinusoidal voltage found relaxation increased hysteresis loop tilt but did not reduce hysteresis. Zero creep was observed at hysteresis loop extremum.
2) Creep experiments varying delay time also increased loop tilt but zero creep locations did not change and coincided with points where loop slope equaled virgin curve slope.
3) Increasing input voltage amplitude did not affect zero creep behavior or virgin curve slope. This characteristic was independent of experiments.
1995 analysis of piezo actuators in translation constructionspmloscholte
1) A translation stage using piezo stacks as actuators was developed to generate displacements with nanometer accuracy over a dynamic range of 10 micrometers. Capacitive sensors were able to measure displacements with subnanometer resolution.
2) Using the high precision measurements from the capacitive sensors, the displacement properties of the piezo actuator in the translation stage could be characterized with great accuracy when different voltages were applied.
3) A model is presented to describe the general behavior of a piezo actuator in a translation stage, and the hysteresis behavior observed in the piezo actuator is found to have point symmetry properties and branches that can be described by third-order polynomials.
The document summarizes a study that characterized the corrosion of a nickel-aluminum (Ni-Al) composite coating compared to a pure nickel coating after 72 hours of immersion in 2M NaCl solution. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used, and scanning electron microscopy was used to examine the corrosion product layers. Results showed the Ni-Al composite had a porous, cracked corrosion product layer that decreased corrosion potential and increased corrosion currents compared to the more protective layer formed on pure nickel. Thus, the Ni-Al composite exhibited lower corrosion resistance than pure nickel in the higher chloride concentration solution.
This document describes the fabrication and electrochemical characterization of carbon nanowalls grown on polycrystalline diamond (CNWs-on-diamond) electrodes. CNWs-on-diamond electrodes were synthesized by DC-PECVD and showed lower background current and larger potential window than CNWs-on-silicon electrodes in cyclic voltammetry measurements. SEM and Raman spectroscopy confirmed the growth of carbon nanowalls on the diamond substrate. The CNWs-on-diamond hybrid structure demonstrates potential for use as an electrode in electrochemical applications and biosensors due to the combined properties of diamond and carbon nanowalls.
This document summarizes research on using electrodeposited manganese dioxide (MnO2) coatings on porous carbon substrates for capacitive deionization (CDI) applications. Two carbon substrates with different surface areas and morphologies were coated with MnO2 using galvanostatic and cyclic voltammetric deposition. Characterization of the coated electrodes found mixed MnO2 phases present. Testing in half-cell configurations showed that maximum ion uptake per mass was not necessarily optimal for practical CDI applications, where performance per electrode area is more important. The results suggest the structure and deposition method can impact how effectively the electrode volume participates in ion removal reactions.
Growth of GaN films on GaAs substrates in an As-free environmentOleg Maksimov
Direct growth of GaN on GaAs substrates in an As-free environment results in a polycrystalline film with misoriented grains and inclusions. Adopting a procedure of substrate nitridation, deposition of a low-temperature GaN buffer layer, and high-temperature overgrowth significantly improves film quality. The improved films have better crystallinity, fewer defects, and a smoother surface morphology. Transmission electron microscopy analysis reveals the films have a columnar structure with straight grain boundaries and defects concentrated at the interface with the GaAs substrate.
“Kinetics and mechanism of sulphuric acid oxidation of glycolic (ga) by selen...آفتاب حسین
This document provides an introduction to a study on the kinetics and mechanism of the oxidation of glycolic acid by selenium dioxide in an aqueous-acid medium. It discusses background information on chemical kinetics, oxidation-reduction reactions, and selenium dioxide as an oxidizing agent. Previous studies on the oxidation of various compounds like ketones using selenium dioxide are also summarized. The document lays out context for investigating the reaction kinetics and mechanism of glycolic acid oxidation.
Anne marie valente feliciano - nucleation of nb films on cu substratesthinfilmsworkshop
In the pursuit of niobium (Nb) films with similar performance with the commonly used bulk Nb surfaces for Superconducting RF (SRF) applications, significant progress has been made with the development of energetic condensation deposition techniques. The controlled incoming ion energy enables a number of processes such as desorption of adsorbed species, enhanced mobility of surface atoms and sub-implantation of impinging ions, thus producing improved film structures at lower process temperatures. All these along with the quality of the Cu substrate have an important influence on the nucleation and subsequent growth of the Nb film, creating a favorable template for growing the final surface exposed to SRF fields. This contribution shows how the structure and defect density thus electron mean free path (represented by residual resistance ratio values) of Nb films can be tailored on Cu substrates, by varying the ion energy and thermal energy provided to the substrate, favoring the hetero-epitaxial or the fiber growth mode.
This document discusses cathodic protection techniques for marine applications. It covers the use of cathodic protection on marine pipelines, offshore structures, and ship hulls. For marine pipelines, coatings are used along with supplemental cathodic protection using sacrificial anodes to protect areas where the coating is damaged. Offshore structures are protected through sacrificial anode systems or hybrid designs using impressed current along with sacrificial anodes. Ship hulls also use coatings along with cathodic protection systems using zinc anodes or impressed current systems on large ships to polarize the structure.
Silicon carbide (SiC) is a wide bandgap semiconductor material useful for high temperature, high power, and high frequency applications. It has exceptional properties like high thermal conductivity, hardness, and electric field breakdown strength. There are over 200 known polytypes of SiC crystal structures defined by their stacking sequences. Common polytypes include 3C, 2H, 4H, 6H and 15R SiC. 4H-SiC has better electrical properties than other polytypes making it suitable for power devices. SiC can be doped n-type or p-type and exhibits high electron and hole mobilities. It is widely used for applications requiring operation at high temperatures and voltages.
This document discusses oxidation in semiconductor device fabrication. It describes oxidation as the process of converting silicon into silicon dioxide, which can occur through dry oxidation using oxygen or wet oxidation using water/steam at high temperatures from 900-1200°C. The key functions of the resulting silicon dioxide layer include acting as a diffusion mask, providing surface passivation and insulation, and enabling device isolation in integrated circuits. The document also classifies oxidation as either diffusion limited or reaction controlled depending on oxide thickness and oxidation time.
Galvanic anodes provide cathodic protection to buried metallic structures using sacrificial anodes made of materials more electronegative than the structure, like magnesium or zinc alloys. The anode material corrodes to provide a protective current without an external power source. Selection involves analyzing performance, cost, and calculating requirements like anode size based on structure size, material properties, design life, and protection criteria. Installation and maintenance costs are generally low for galvanic systems.
This document discusses cathodic protection, which involves applying a small electric current to the surface of a metal structure to prevent corrosion. It describes two main methods: impressed current uses an external power source connected between the structure and an auxiliary anode buried in the ground, while sacrificial anodes rely on galvanic action between the structure and more reactive anodes. The principles of cathodic protection involve driving the structure's potential negative of its corrosion potential to inhibit the corrosion reaction while increasing the cathodic reaction. Proper design considers factors like protection potentials, current density, coatings, and avoiding over-protection.
Phillips - Atomic Layer Deposition of NbN Thin Films for Superconducting Radi...thinfilmsworkshop
http://www.surfacetreatments.it/thinfilms
Atomic Layer Deposition of NbN thin films for SRF applications (Larry Phillips - 15')
Speaker: Larry Phillips - Jefferson Lab - Newport News - Virginia | Duration: 15 min.
Abstract
Niobium Nitride is a 17K superconductor investigated since early eighthies for Superconducting Radiofrequency applications.
Atomic Layer deposition is instead a technique that only recently starts to be considered for industrial applications.
Electrical Properties of Reservoir RocksShah Naseer
The document discusses electrical properties of reservoir rocks and methods for determining fluid saturations. It explains that electrical resistivity is a measure of how much electrical current can flow through a material and is affected by porosity, pore fluid type and saturation, and lithology. Common methods to determine fluid saturations include well log analysis, core analysis, and capillary pressure measurements. Resistivity is highest for gas, intermediate for oil, and lowest for water-saturated rocks. Resistivity decreases as water saturation increases. Equations are presented relating true resistivity to water resistivity, porosity, and water saturation.
THE UTILISATION OF 2-D RESISTIVITY AND INDUCED POLARIZATION (IP) METHODKasdi Nata Sujono
The document summarizes a study that used 2-D resistivity and induced polarization (IP) methods to determine iron ore bodies at Kampung Melaka, Kuala Lipis, Pahang, Malaysia. Three survey lines totaling 600 meters were divided into lots of 200 meters each. The 2-D resistivity method identified iron ore by its low resistivity, while IP differentiated iron ore and groundwater. Results showed iron ore underlying the surface from 5-30 meters was mostly located in lots 1 and 2 based on their low resistivity. Lot 1 contained 20-25% iron ore, lot 2 contained 30-35% iron ore, and lot 3 contained 15-20% iron ore over each 200-meter
Temperature Dependence of the Band-Edge Transitions of ZnCdBeSeOleg Maksimov
This study characterized the temperature dependence of band-edge transitions in three ZnCdBeSe films with varying concentrations of beryllium (Be) using contactless electroreflectance (CER) and piezoreflectance (PzR) measurements from 15-450K. The CER and PzR spectra showed doublet features near the band edge, indicating light-hole and heavy-hole excitonic transitions. Comparing the relative intensities of the PzR and CER spectra allowed identification of the transitions. Analysis of the temperature dependence provided information on how the energy and broadening of the transitions varied with temperature and Be concentration. The results showed that incorporating Be effectively reduced the rate of temperature variation of the energy
The document reviews silicon carbide (SiC) based power semiconductor devices and their applications. It discusses how the superior material properties of SiC, such as its wide bandgap, high electric field, and high thermal conductivity, allow it to handle higher power ratings, switching frequencies, and operating temperatures compared to silicon-based devices. The document provides an overview of the available SiC power devices, including diodes and MOSFETs, and compares the theoretical advantages of SiC devices to silicon, such as their thinner depletion widths, lower on-state resistances, and higher breakdown voltages. It also briefly discusses potential converter topologies that can benefit from using SiC semiconductor devices.
1. Electron irradiation of sapphire (Al2O3) results in both electronic and nuclear damage.
2. Electronic damage includes electron excitation and ionization via interactions between the incident 1 MeV electrons and the aluminum and oxygen atoms in Al2O3.
3. Nuclear damage, or displacement damage, occurs when electrons transfer sufficient energy to atomic nuclei to displace them from their lattice sites, calculated using models of electron-atom cross sections and displacement thresholds.
1999 observation of zero creep in piezoelectric actuatorspmloscholte
The document summarizes experiments on piezoelectric actuators that observe zero creep in certain locations of the hysteresis loop. Specifically:
1) Relaxation experiments using an offset sinusoidal voltage found relaxation increased hysteresis loop tilt but did not reduce hysteresis. Zero creep was observed at hysteresis loop extremum.
2) Creep experiments varying delay time also increased loop tilt but zero creep locations did not change and coincided with points where loop slope equaled virgin curve slope.
3) Increasing input voltage amplitude did not affect zero creep behavior or virgin curve slope. This characteristic was independent of experiments.
1995 analysis of piezo actuators in translation constructionspmloscholte
1) A translation stage using piezo stacks as actuators was developed to generate displacements with nanometer accuracy over a dynamic range of 10 micrometers. Capacitive sensors were able to measure displacements with subnanometer resolution.
2) Using the high precision measurements from the capacitive sensors, the displacement properties of the piezo actuator in the translation stage could be characterized with great accuracy when different voltages were applied.
3) A model is presented to describe the general behavior of a piezo actuator in a translation stage, and the hysteresis behavior observed in the piezo actuator is found to have point symmetry properties and branches that can be described by third-order polynomials.
1996 interactions between adsorbed si dimers on si(001)pmloscholte
1) The interactions between adsorbed silicon dimers on a silicon 001 surface were studied using scanning tunneling microscopy.
2) It was found that by increasing the tip-sample voltage, transitions between clusters of dimers could be induced. These field-enhanced transitions allowed the interactions between dimers to be clarified.
3) Two dimers in a BB configuration were found to interact strongly, forming a faintly visible "twin" structure. In contrast, dimers in an AB configuration showed little interaction.
1998 growth pyramids on si(111) facets a cvd and mbe studypmloscholte
1) The morphology of growth pyramids formed on Si(111) facets during CVD growth was studied using atomic force microscopy.
2) Spiral and concentric step edge patterns were observed on the pyramid tops, indicating the pyramids originated from different types of dislocations.
3) The step edge patterns and sharp corners suggest growth during CVD is governed by step edge processes and surface diffusion is not rate limiting.
1997 room temperature growth of submonolayers of silicon on si(001) studied w...pmloscholte
1) Room-temperature growth of submonolayers of silicon on Si(001) was studied using scanning tunneling microscopy (STM).
2) At low coverages, adatoms aggregate into dimers in different geometries (A, B, C, D). A kinetic model is proposed for dimer formation.
3) At higher coverages, dimers line up to form linear structures in the [110] and [310] directions. Near 0.2 ML coverage, these lines merge to form a random network that later converts into epitaxial dimer rows above 0.2 ML.
1997 sodium doped dimer rows on si(001)pmloscholte
1) The stability and electronic structure of a sodium-doped silicon dimer row on the hydrogen-passivated Si(001) 2x1 surface is studied using first-principles calculations.
2) It is predicted that sodium atoms evaporated onto the surface will stick preferentially to the depassivated dimer row.
3) This leads to a partially filled empty one-dimensional state of the dimer row, making it metallic in character and behaving as a thin metallic nanowire of atomic dimensions.
1992 asymmetrical dimers on the ge(001) 2 × 1-sb surface observed using x-ray...pmloscholte
The document summarizes a study that used x-ray diffraction to determine the atomic structure of the 2x1 reconstruction on the Ge(001) surface induced by antimony (Sb) adsorption. The key findings are:
1) Sb forms asymmetric dimers on the Ge(001) surface, replacing the symmetric Ge dimers, with a bond length of 2.90 Angstroms and a midpoint shift of 0.16 Angstroms.
2) This is the first reported asymmetric dimer structure for a group IV/V system, in contrast to the symmetric dimers typically observed for systems like As/Si(001).
3) Relaxations of the top four substrate layers were also measured and compared
1998 epitaxial clusters studied by synchrotron x ray diffraction and scanning...pmloscholte
1) The document summarizes studies of three nanoscale cluster systems using synchrotron X-ray diffraction and scanning tunneling microscopy: Ge hut clusters on Si(001), In clusters on Ge(001) that form 103 facets, and wedge-shaped Cu clusters buried in Cu films on Ni(001).
2) X-ray diffraction is used to determine the fundamental structural properties of the clusters, such as strain relaxation, by measuring crystal truncation rods from the cluster facet planes.
3) For the Ge/Si system, diffraction data found strain relaxation of 0.5-4% within the hut clusters. For the In/Ge system, clusters were completely relaxed from the substrate with In atoms stabilizing the
2001 field based scanning tunneling microscope manipulation of antimony dimer...pmloscholte
This summary provides the key details from the document in 3 sentences:
The document discusses an experiment that investigated manipulating antimony dimers (Sb2) on the silicon (001) surface using a scanning tunneling microscope (STM). Directed movement of Sb2 dimers was achieved through an asymmetric scanning technique of the STM tip, where parameters were varied between left-to-right and right-to-left scanning to create a preferential direction for the dimers to move. While the yield for directed manipulation was low, statistics on enhanced hopping rates of Sb2 dimers are reported and models involving an induced dipole interaction between the tip and dimer are discussed as explanations for the observed behavior.
The document discusses the formation of nickel silicide (NiSi) on electrochemically etched silicon nanowires (SiNWs). Specifically, it summarizes that 1) SiNWs were fabricated via electroless etching and deposited on lithographically patterned nickel electrodes, 2) thermal annealing was used to form self-aligned NiSi contacts between the SiNWs and electrodes as evidenced by TEM, XPS and XANES characterization, and 3) electrical measurements showed ohmic behavior after silicidation, indicating lateral NiSi formation along the SiNWs.
Thermal conductivity of lightly sr and zn-doped la2 cuo4 single crystalsSuresh Bhardwaj
Thermal conductivity measurements were taken on lightly Sr- and Zn-doped La2CuO4 single crystals from 2-300 K. It was found that even very low doping levels significantly suppressed the low-temperature phonon peak in thermal conductivity. The suppression of the phonon peak was greater in the c-axis than the ab-plane for Sr doping, but the opposite was true for Zn doping. Comparison with undoped La2CuO4 suggests the static spin stripes present in lightly doped La2CuO4 are playing an important role in damping the phonon heat transport, particularly for the c-axis.
The document discusses two types of superconductors:
Type I superconductors strictly follow the Meissner effect and exhibit perfect diamagnetism below a critical field, above which superconductivity is lost abruptly. Type II superconductors do not follow the Meissner effect strictly and have higher critical fields, existing in a mixed state between lower and upper critical fields where magnetic flux partially penetrates. The document provides examples of the magnetic behavior of type I and type II superconductors.
This document summarizes the electrical characteristics of a suspended silicon nanowire single-hole transistor containing silicon nanocrystals less than 10 nm in size. Coulomb diamonds were observed in the electrical measurements at 10 K, indicating single-hole tunneling through a dominant nanocrystal. The Coulomb diamonds had a charging energy of approximately 27 meV. Additionally, resonant tunneling features with an energy spacing of around 10 meV were observed parallel to both edges of the Coulomb diamonds. These features could be associated with either excited hole states or interactions between holes and acoustic phonons in the nanocrystal.
Electrical transport and magnetic interactions in 3d and 5d transition metal ...ABDERRAHMANE REGGAD
The document discusses electrical transport and magnetic interactions in 3d and 5d transition metal oxides. It summarizes that for decades, transition metal oxides have been explored where exotic states like high-Tc superconductivity and colossal magnetoresistance emerge due to cooperative interactions between spin, charge, and orbital degrees of freedom. The document then examines various phenomena in transition metal oxides including Mott insulators, double exchange mechanism, and the Kitaev-Heisenberg model observed in iridate compounds like Na2IrO3 which may realize a spin liquid ground state.
This document summarizes a study that investigated the local electronic structure of lithium-doped zinc oxide (ZnO:Li) thin films using X-ray absorption spectroscopy. The researchers found that lithium ions substituted for zinc sites in the wurtzite crystal structure without forming secondary phases, as evidenced by X-ray diffraction. Electrical measurements showed the films became p-type conductive with lithium doping levels between 1-5% atomic concentration. Analysis of X-ray absorption near-edge spectroscopy data revealed lithium doping decreased both the zinc-oxygen and zinc-zinc bonding lengths, consistent with lithium incorporation into the ZnO lattice.
Synthesis and Dielectric Characterization of Barium Substituted Strontium Bis...ijrap
The strontium bismuth niobate, SrBi2Nb2O9 (SBN) is a bismuth layered perovskite oxide
compound with potentially useful ferroelectric properties which offer several advantages such as fatigue
free, lead free, low operating voltages, relatively high Curie temperature; and most importantly, their
ferroelectric properties are independent of film thickness. These materials are also important for Fe-RAM
applications having large remanent polarization and low coercivity accompanied by high Curie
temperature for better performance and reliable operation. Present paper describes synthesis, dielectric
properties and impedance studies to reveal the important properties of barium substituted strontium
bismuth niobate, Sr0.85Ba0.15Bi2Nb2O9 in the system Sr1-xBaxBi2Nb2O9(x=0.15).
SYNTHESIS AND DIELECTRIC CHARACTERIZATION OF BARIUM SUBSTITUTED STRONTIUM BIS...ijrap
The strontium bismuth niobate, SrBi2Nb2O9 (SBN) is a bismuth layered perovskite oxide
compound with potentially useful ferroelectric properties which offer several advantages such as fatigue
free, lead free, low operating voltages, relatively high Curie temperature; and most importantly, their
ferroelectric properties are independent of film thickness. These materials are also important for Fe-RAM
applications having large remanent polarization and low coercivity accompanied by high Curie
temperature for better performance and reliable operation. Present paper describes synthesis, dielectric
properties and impedance studies to reveal the important properties of barium substituted strontium
bismuth niobate, Sr0.85Ba0.15Bi2Nb2O9 in the system Sr1-xBaxBi2Nb2O9(x=0.15).
This document calculates and compares the electron mobility in wurtzite (WZ) and zincblende (ZB) forms of aluminum nitride (AlN) using an iterative method. It solves the Boltzmann transport equation taking into account various scattering mechanisms between 100-600K. Total scattering rates in WZ-AlN are higher than in ZB-AlN due to differences in bandgap and electron effective mass. Electron mobility is higher in WZ-AlN (337.61 cm2/V-s at 300K) than ZB-AlN (152.254 cm2/V-s) and decreases with increasing temperature and electron concentration in both structures.
Silicon is the most abundant element in the Earth's crust and is commonly found in dust, sands, and rocks. It is a metalloid that is tetravalent and forms covalent bonds. Silicon is a semiconductor and forms the base material for many electronic devices. Some key electronic devices that use silicon include diodes, transistors, solar cells, and integrated circuits. These devices exploit the electrical properties of doped silicon and p-n junctions to control and modulate the flow of electrons.
1998 epitaxial film growth of the charge density-wave conductor rb0.30 moo3 o...pmloscholte
1) Thin films of the charge density wave compound Rb0.30MoO3 were grown on SrTiO3 (001) substrates using pulsed laser deposition.
2) Initial growth proceeds through the formation of uniform, droplet-shaped islands that are fully relaxed. Thicker films form larger clusters that differ in size and have asymmetric shapes with clear facets.
3) X-ray diffraction shows the films have a preferred out-of-plane growth direction and four in-plane orientations corresponding to the symmetry of the SrTiO3 substrate. The correlation length perpendicular to the charge density wave axis is smaller than the dimensions of the grain clusters in thicker films.
Surface carrier recombination of a si tip under high electric fieldbmazumder
Using laser assisted atom probe tomography, the authors investigated surface recombination processes of a silicon tip under high electric field by changing the laser wavelength. They found that with infrared laser light, the evaporation rate showed a wide peak indicating a long electron-phonon relaxation time at the surface. However, with green laser light, the silicon peaks in the ion flight time spectrum were well resolved even at high laser intensity, demonstrating that this behavior is common to indirect bandgap semiconductors. The authors developed a simple model to explain the laser wavelength dependence and estimate the surface recombination time.
This document discusses thermoelectric materials and calculations using the Wien2K software. It describes the Seebeck effect and Peltier effect. It discusses using Wien2K to model materials like Mg2Si, calculate properties like density of states, band structure, and optimize volume. Modifying approximations, strain effects, and nanostructuring are discussed to increase thermoelectric figure of merit ZT by increasing power factor and decreasing thermal conductivity.
Experiment Form 4 Chapter 6 ElectrochemistryMISS ESTHER
Experiment 6.8 investigates displacement reactions between metals and their salt solutions to construct an electrochemical series. The procedure involves placing different metal strips (magnesium, zinc, lead, copper) into separate salt solutions (magnesium nitrate, zinc nitrate, lead nitrate, copper nitrate). Observations are made to check for any color changes in the solutions, solid deposits on the metals, and metal dissolution. It is hypothesized that the greater the number of metals that can displace a metal from its salt solution, the higher its position will be in the electrochemical series.
Dendritic Electroless Deposits of Lead From Lead Acetate Solutioninventionjournals
Electroless deposition of lead from lead acetate is studied in a planar cell geometry. Dendritic patterns are grown using electroless deposition in planar cell geometry. Electroless deposition cell is designed and constructed and the depositions obtained are analysed for self similarity and fractal characterization. Details and findings are presented
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
Final-Investigation into interlayer interactions in MoSe2André Mengel
1) The document describes an investigation of interlayer interactions in MoSe2-WSe2 heterostructures fabricated on different substrates. 2) Heterostructures were fabricated using mechanical exfoliation and stacking of monolayers, and were characterized using photoluminescence spectroscopy and atomic force microscopy. 3) Preliminary results showed strong photoluminescence from the WSe2 monolayer in all structures, but the charge transfer exciton peak was not observed, requiring further investigation.
Similar to 2000 surface polymerization of epitaxial sb wires on si(001) (20)
1998 Appl. Phys. A 66 (1998), p857 design and construction of a high resoluti...pmloscholte
The document describes the design and construction of a high-resolution 3D translation stage for a scanning tunneling microscope (STM) equipped with a newly developed capacitive translation sensor. Key points:
1) The sensor can measure translations in the lateral and perpendicular directions with sub-angstrom resolution.
2) In combination with a model-based digital feedback system, the sensor and stage will enable accurate probe positioning and control, making the STM suitable for metrological applications.
3) The capacitive sensor can detect translations in three dimensions with resolutions of 30 picometers laterally and 10 picometers perpendicular to the surface.
1996 a calibrated scanning tunneling microscope equipped with capacitive sensorspmloscholte
1) A scanning tunneling microscope equipped with capacitive sensors has been developed to measure the real-time X-Y position and correct for errors caused by piezoelectric actuator properties like hysteresis and nonlinearity.
2) The microscope uses a calibrated scanning stage with capacitive sensors that measure the actual X-Y position and provide feedback to dynamically adjust the piezo voltages to reach the desired scanning positions with minimal error.
3) This allows surfaces to be scanned geometrically accurately while correcting for drift and low-frequency vibrations in real time.
1994 restoration of noisy scanning tunneling microscope imagespmloscholte
This document compares and improves several implementations of the Wiener filter to remove noise from Scanning Tunneling Microscope (STM) images. It finds that the implementation by Weisman et al. using the noise model of Stoll et al. provides the best performance on both simulated and real STM images. It tests the filters on simulated graphite images with added 1/f noise and finds the modified Weisman filter performs significantly better than other implementations on a real STM graphite image due to deviations from the 1/f noise model.
1998 characterisation of multilayers by x ray reflectionpmloscholte
This document presents a theoretical model for characterizing multilayers using X-ray reflection. The model includes refraction effects and describes diffuse scattering from multilayers with roughened interfaces, including islands and miscut-induced steps. The model calculates X-ray intensity profiles that can be compared to experimental data to deduce the morphology of interfaces, such as mean island size and average step height. The model is applied to experimental data from a Si/Ge multilayer and results in values consistent with AFM images.
1997 nucleation of homoepitaxial si chains on si(001) at room temperaturepmloscholte
1) Si dimers initially adsorb at preferred sites on the Si(001) surface, with most occupying C-positions.
2) Interactions between dimers and diffusing adatoms lead to the formation of three-atom clusters like twins and crosses. These can extend into diluted lines of C dimers along [110] and [310] directions.
3) Upon further deposition, the diluted dimer lines transform into epitaxial dimer rows through a process starting at the line ends of reorienting dimers and adding mobile adatoms.
1997 atomic details of step flow growth on si(001)pmloscholte
1. The study uses scanning tunneling microscopy to observe atomic details of step flow growth on the Si(001) surface at the single adatom level.
2. Empty state images clearly show single adatoms bound to step edges, revealing stable binding sites. Subsequent addition of adatoms forms different step edge configurations.
3. Dynamic processes are also observed, including adatom diffusion along step edges between stable binding sites and dimer formation between two adatoms.
4. Different step edge configurations are stable and can serve as sites for other processes, such as creating single dimer vacancies, providing insight into growth mechanisms.
1996 strain in nanoscale germanium hut clusters on si(001) studied by x ray d...pmloscholte
This document summarizes a study that used x-ray diffraction and scanning tunneling microscopy to investigate the strain in nanoscale germanium hut clusters on silicon substrates. The key findings are:
1) X-ray diffraction measurements revealed contributions from the hut clusters that allowed determining the strain distribution uniquely from the clusters.
2) The germanium clusters are almost fully strained with 0.5% misfit at the interface but strain is relaxed towards the apex, with 4.2% misfit indicating the natural germanium lattice spacing.
3) By modeling the asymmetric intensity distributions around diffraction peaks, the study determined that strain is relaxed uniformly through the hut clusters from a maximum near the interface to a minimum
1996 origin of rippled structures formed during growth of si on si(001) with mbepmloscholte
The document summarizes research into the origin of rippled structures that form on the surface of silicon during molecular beam epitaxy growth on Si(001) substrates. Through experiments using x-ray crystallography, optical microscopy, and atomic force microscopy, the researchers found that the rippled structure is caused by correlated kink bunching along step edges, rather than by step bunching. They present a model wherein the inherent discreteness of growth can cause deviations from the equilibrium kink distribution large enough to induce step-step interactions and the formation of ripples.
1996 new application of classical x ray diffraction methods for epitaxial fil...pmloscholte
This document describes a new method for using classical X-ray diffraction to characterize epitaxial thin films. The method combines powder diffraction data with a Weissenberg camera technique to provide a complete overview of the in-plane and out-of-plane characteristics of the film and its relationship to the substrate in just two scans. This includes information on the film's orientation, strain, texture, and lattice parameters relative to the substrate. The method is illustrated using several epitaxial film/substrate systems and provides structural information simply and reliably using standard laboratory X-ray equipment.
1996 atomic force microscopy study of (001) sr tio3 surfacespmloscholte
The document summarizes an atomic force microscopy study of SrTiO3 surfaces after different heat treatments. The key points are:
1) Annealing in O3 results in atomically flat terraces separated by smooth, one unit cell high steps that follow the substrate's miscut orientation.
2) Annealing in O2 produces irregularly shaped terraces with step heights varying between 0.5-2.5 unit cells. Line defects and holes are also observed.
3) Depositing SrTiO3 on a surface annealed in O3 increases roughness due to island formation but heals line defects.
4) Annealing in UHV produces rougher steps and surface clusters, indicating a
1995 mechanism of the step flow to island growth transition during mbe on si(...pmloscholte
The document discusses the transition between step flow and island growth during molecular beam epitaxy of silicon on a silicon (001) surface with dimer rows. It finds that:
1) For typical experimental conditions, diffusion perpendicular to the dimer rows cannot be neglected and a transition occurs from effectively 1D to 2D diffusion as the terrace width increases.
2) When including 2D diffusion, the critical flux for the step flow to island growth transition scales as the terrace width to the -4th power for large terraces, but as the terrace width to the -3rd power for small terraces.
3) Comparing to experimental data, accounting for diffusion perpendicular to the dimer rows is essential
1995 growth mechanisms of coevaporated sm ba2cu3oy thin filmspmloscholte
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
1994 the influence of dimerization on the stability of ge hutclusters on si(001)pmloscholte
1) The epitaxial growth of Ge on Si(001) initially proceeds two-dimensionally but then forms three-dimensional Ge nanocrystals called "hutclusters".
2) Hutclusters have well-defined, highly anisotropic shapes bounded by (105) facets, which is surprising since (105) facets are normally not stable for macroscopic crystals.
3) The paper presents a model to explain the stability and morphology of hutclusters, identifying the key parameters of strain from lattice mismatch, nanocrystal size, and surface energies of the substrate and nanocrystal facets.
1994 nucleation and growth of c parallel grains in co-evaporated sm ba2cu3oy ...pmloscholte
1) The study investigates the nucleation and growth of c-parallel (c//) grains in co-evaporated SmBa2Cu3Oy films using scanning tunneling microscopy, x-ray diffraction, and transmission electron microscopy.
2) It was found that the volume fraction of c// grains increases with increasing supersaturation during film growth, indicating that kinetic factors like reduced surface mobility promote c// nucleation over c-perpendicular growth.
3) No evidence was found of a critical thickness for a switch from c-perpendicular to c// growth; instead, c// grains nucleate throughout film growth when supersaturation is high.
1994 atomic structure of longitudinal sections of a pitch based carbon fiber ...pmloscholte
1) STM images of longitudinal sections of pitch-based carbon fibers revealed a hexagonal superstructure with a periodicity of 14.9 A, indicating the top graphitic plane was rotated 9.5" from the underlying bulk.
2) Near defects, this superstructure was modulated with a (6 x fi)R30" pattern. The same modulation was found in images showing atomic resolution.
3) Power spectra of modulated regions contained extra peaks corresponding to the (6 x fi)R30" pattern, in addition to the six peaks from the hexagonal graphitic structure. This indicates the atomic structure is disturbed to a depth of at least two layers from the surface.
1992 schottky barrier formation in conducting polymerspmloscholte
1. The authors studied thin films of poly(3-hexylthiophene) (PHT) and polypyrrole (PPY) on highly oriented pyrolytic graphite using scanning tunneling microscopy.
2. They observed semicrystalline order in the form of micro-islands connected by parallel polymer strands. The orientation of the strands is determined by the substrate.
3. For PPY films, they observed superhelical structures not previously reported. The apparent height of polymer strands was found to differ for positive and negative bias voltages, which the authors attribute to the formation of a Schottky barrier between the metallic tip and semiconducting polymer.
1990 crystallization kinetics of thin amorphous in sb filmspmloscholte
1) Evaporated and sputtered InSb films have different crystallization properties. Evaporated films have a lower activation energy of 1.39 eV and crystallize by three-dimensional growth on existing nuclei.
2) Sputtered films have a higher activation energy of 2.7 eV and crystallize by nucleation and subsequent growth on the nuclei. The Avrami exponent indicates sputtered films require crystalline nuclei to form before crystallization can begin.
3) Transmission electron microscopy images show evaporated films have existing nuclei while sputtered films have no visible crystallites in the as-deposited state, requiring nucleation.
1989 optical measurement of the refractive index, layer thickness, and volume...pmloscholte
This document discusses a method for determining the complex refractive index, layer thickness, and volume changes of thin films using optical measurements. The method involves measuring reflectance and transmittance values across a range of intentionally varied layer thicknesses, rather than fitting those values as functions of independently measured thicknesses. The measurements provide information needed for optical recording applications. The complex refractive index, layer thicknesses, and volume changes can then be unambiguously calculated by fitting curves to the reflectance-transmittance plane measured across multiple thicknesses. An example application determines these properties for thin films of GaSb and InSb for use in optical recording.
1988 a study of the thermal switching behavior in gd tbfe magneto‐optic films...pmloscholte
1) A study examined the thermal switching behavior of GdTbFe magneto-optic films using two laser beams - a krypton laser (753 nm) to locally heat spots and a semiconductor laser (820 nm) to monitor changes in magnetization.
2) It was observed that magnetization reversal within the heated spots was delayed after the start of heating, with delay times ranging from 200 microseconds to 2 seconds depending on factors like applied field and heating power.
3) Analysis indicated the delayed switching was partly due to the time needed to reach the temperature required for reversal as the spot heated up, though other magnetic processes may also have contributed to the delay.
Andreas Schleicher presents PISA 2022 Volume III - Creative Thinking - 18 Jun...EduSkills OECD
Andreas Schleicher, Director of Education and Skills at the OECD presents at the launch of PISA 2022 Volume III - Creative Minds, Creative Schools on 18 June 2024.
Elevate Your Nonprofit's Online Presence_ A Guide to Effective SEO Strategies...TechSoup
Whether you're new to SEO or looking to refine your existing strategies, this webinar will provide you with actionable insights and practical tips to elevate your nonprofit's online presence.
THE SACRIFICE HOW PRO-PALESTINE PROTESTS STUDENTS ARE SACRIFICING TO CHANGE T...indexPub
The recent surge in pro-Palestine student activism has prompted significant responses from universities, ranging from negotiations and divestment commitments to increased transparency about investments in companies supporting the war on Gaza. This activism has led to the cessation of student encampments but also highlighted the substantial sacrifices made by students, including academic disruptions and personal risks. The primary drivers of these protests are poor university administration, lack of transparency, and inadequate communication between officials and students. This study examines the profound emotional, psychological, and professional impacts on students engaged in pro-Palestine protests, focusing on Generation Z's (Gen-Z) activism dynamics. This paper explores the significant sacrifices made by these students and even the professors supporting the pro-Palestine movement, with a focus on recent global movements. Through an in-depth analysis of printed and electronic media, the study examines the impacts of these sacrifices on the academic and personal lives of those involved. The paper highlights examples from various universities, demonstrating student activism's long-term and short-term effects, including disciplinary actions, social backlash, and career implications. The researchers also explore the broader implications of student sacrifices. The findings reveal that these sacrifices are driven by a profound commitment to justice and human rights, and are influenced by the increasing availability of information, peer interactions, and personal convictions. The study also discusses the broader implications of this activism, comparing it to historical precedents and assessing its potential to influence policy and public opinion. The emotional and psychological toll on student activists is significant, but their sense of purpose and community support mitigates some of these challenges. However, the researchers call for acknowledging the broader Impact of these sacrifices on the future global movement of FreePalestine.
Level 3 NCEA - NZ: A Nation In the Making 1872 - 1900 SML.pptHenry Hollis
The History of NZ 1870-1900.
Making of a Nation.
From the NZ Wars to Liberals,
Richard Seddon, George Grey,
Social Laboratory, New Zealand,
Confiscations, Kotahitanga, Kingitanga, Parliament, Suffrage, Repudiation, Economic Change, Agriculture, Gold Mining, Timber, Flax, Sheep, Dairying,
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
Gender and Mental Health - Counselling and Family Therapy Applications and In...PsychoTech Services
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
This presentation was provided by Racquel Jemison, Ph.D., Christina MacLaughlin, Ph.D., and Paulomi Majumder. Ph.D., all of the American Chemical Society, for the second session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session Two: 'Expanding Pathways to Publishing Careers,' was held June 13, 2024.
2. 15 342 BRIEF REPORTS PRB 62
FIG. 1. STM image of Sb 1 2 growth on the 2 1 Si(001)
surface at 575 K 0.1 nA, bias referred to substrate Sb lines extend
from two to about 12 dimers 5 nm . Note the splitting of the Sb
dimer row into a ‘‘double’’ line similar to the Si * orbital in the
FIG. 2. STM image of 0.23 ML of Sb on Si 001 at 1.2V subs
empty state image. Most of the Sb dimer rows terminate between
and 0.1 nA annealed at 600 K. The inset shows the upper left region
the chains of the Si. In the schematic the Sb line is shown with
at 1 V. No dark disorder patches are observable as well as no
the two possible termination types: on a former Si dimer row left
chemical contrast. This is consistent with Sb on Si; however, dif-
and between dimer rows right, occurs much more frequently .
ferent from what Garni et al. reported in their Figs. 4 c and 4 d
under similar conditions.
no three-dimensional growth up to the desorption tempera-
ture of the Sb. for 5 min. We speculate that the Sb has desorbed from the
When the surface is annealed at 575 K the Sb orders into surface and is not incorporated into the substrate which is
short lines up to 5 nm orthogonal to the Si dimer rows as consistent with work done by Wasserfall and Ranke.13
shown in Fig. 1. We observe 1 2 epitaxial growth of Sb on We have performed local density of states measurements
the 2 1 reconstructed Si which is consistent with the study of the Sb clusters, lines, and islands by means of scanning
by Richter et al.7 of 820 K annealed Sb layers 0.6 ML and tunneling spectroscopy. The feedback loop is opened after
more , leading to three-dimensional growth. The schematic stabilizing the tunneling gap ‘‘freezing’’ the tip position
in Fig. 1 shows the structure of the Sb2 adsorption and the and we record the current as a function of voltage, I(V).
1 2 growth of the Sb dimer rows. We have varied the Sb2 This is done in a grid of points on the surface and several of
coverage from 1% to 70% and the annealing temperature these curves were averaged at distinct features e.g., Sb2
from 525 to 600 K as well as the annealing time and always dimer .
find the same maximum length of Sb lines. Figure 3 shows the spatially resolved density of states of
It is essential to demonstrate that we indeed observe Sb an epitaxial Sb line on Si. This spectroscopy data were taken
structures on Si and not Si on Si. Starting from a low cover- after an anneal at 575 K. These topography of the 3D image
age of Sb Garni et al.9 also observed the formation of dimer reflects the constant current scan with several free Sb2
rows on the surface. However, in contrast to our work and dimers and a Sb dimer row. The brightness indicates the
earlier studies they argue that these consist of Si which was density of states at the Fermi level. The area with a finite
replaced by Sb in the terrace structure at temperatures above density of states is always restricted to the end of Sb lines.
460 K leading to Si2 ad-dimers. The key observations of Ref. The dI/dV spectra of free Sb2 dimers show a gap similar to
9 are the chemical contrast observed at low negative sample Si. The I(V) inset shows the region around the Fermi energy
bias and a high defect density on the Sb:Si 001 surface. We where the ends of the Sb dimer row show a finite slope in
performed these experiments in the temperature and cover- contrast to the Sb line center and the Si.
age range stated in the previous paragraph and observe no The normalized numerical derivative of the spectroscopy
increase in the number of defects after annealing. Further- data in Fig. 3 is presented in Fig. 4 over the full acquired
more, we observe no chemical contrast: no dark disordered energy range. It shows three distinct classes of curves: first,
regions appear when scanning at low bias as shown in Fig. 2. the Sb2 dimer with a low state density near E F and a peak in
Additionally, the observed epitaxial lines are limited to a the LDOS at a valence energy deeper than the Si; second, the
maximum length of 5 nm which is inconsistent with Si on enhanced LDOS near E F 0.5 eV and finite LDOS at E F for
Si 001 . Much longer epitaxial lines are observed for Si on the Sb-line end; and third, the center of the Sb line with
Si.10 We conclude that we observe Sb2 dimers and dimer almost identical LDOS as the bare Si 001 2 1. Not shown
rows on Si which is consistent with earlier studies.6–8,11,12 in the figure is spectroscopy averaged over a Sb4 cluster.
Further annealing of the sample at 700 K leads to the Spectroscopy curves of Sb4 clusters display very little struc-
conversion of the Sb dimer rows to islands. The amount of ture and are lower in amplitude compared to the Si and the
Sb on the surface does not change during the conversion of other Sb structures. This may be attributed to weak bonding/
Sb2 dimers to the islands. This was confirmed by annealing a coupling to the substrate of this nonepitaxial cluster. The
sample with a certain Sb coverage from free Sb dimers to Sb results demonstrate a significant change of the observed
dimer rows and then to the Sb islands while analyzing the Sb LDOS when the Sb2 is incorporated in a Sb dimer row.
surface coverage in the STM images. The maximum length The Si 001 2 1 surface shows the bonding and anti-
of Sb rows in these islands is about 8 nm which is consider- bonding * state as shown clearly in Fig. 4. The observa-
ably longer than the Sb lines with a maximum of 5 nm. A tions confirm the identical behavior of the center of the Sb
clean 2 1 Si surface reestablishes after an anneal at 775 K line and the Si in contrast to the end state which peaks closer
3. PRB 62 BRIEF REPORTS 15 343
FIG. 3. Color Epitaxial Sb line on Si 2
1. The apparent height reflects the topography
at 2V sam ple and the color the magnitude of
dI/dV at 0 V as shown in the I(V) inset from
blue over red to white for 0 to 2pA/V). Only the
ends of the Sb line show a finite density of states
at the Fermi level marking the reactive sites of
the surface polymerization in contrast to the free
Sb2 dimers the two dimers on the upper left are
separated by a * chain and not bonded like a Sb
line . The vertical scale is exaggerated, the Sb2
dimers and Sb line appear as 0.1 nm features in
the scan.
to the Fermi level. It is interesting to note that the Sb lines the growth kinetics. We think that the findings for Si on
show a more pronounced * -like feature than the Si which Si 001 must be attributed to a similar origin as for Sb on
is consistent with the clear antibonding like character of the Si 001 . The 1D growth of Sb on Si 001 is based on the
Sb line as shown in the empty state image of Fig. 1. This is higher probability of an ad-dimer to stick to the end of the Sb
surprising since one could expect an occupied * orbital line versus the side of the line. The observation of a finite
when the lone pairs of the Sb atoms hybridize. Thus, the density of states at the Fermi level uniquely links the growth
state we observe is most likely not just a * state but a mode to the microscopic electronic properties of the struc-
different antibonding orbital of the complicated Sb on the Si ture.
system. The ends of the Sb line show a finite density of states The reactive end is the nucleation site for the next build-
at E F but we still observe a peak in the LDOS at ing block of the polymer chain as shown in the schematic of
0.5 eV. We speculate that this may be due to the interac- Fig. 1 at, e.g., the left end of the Sb line. A Sb2 dimer can
tion between the two dangling bonds of the reactive site. bond to the two dangling bonds and extend the chain by
A central result of the spectroscopy work is the observa-
breaking the bond of the next Si2 dimer. The next step is
tion of a finite density of states at the Fermi level for the ends
identical to an addition on the right end of the Sb line in Fig.
of the Sb dimer rows. A finite density at the Fermi level is
the signature of a reactive site like a dangling bond. A dan- 1 where the strained bond needs to be broken to add a
gling bond is half filled and so is expected to result in a finite dimer to the Sb line. The process then repeats until the added
slope of the I(V) curve at zero bias finite LDOS . To our strain discussed below in the Sb line is larger than the gain
knowledge this is the first direct observation of the reactive in energy due to the bonding.
end of a structure leading to surface polymerization as pre- The existence of the end state does not depend on the total
dicted by Brocks et al. Ganz et al. studied the 1D growth of length of the Sb line as we have observed in Sb lines ranging
Si on Si 001 and speculated that ‘‘sticky ends’’ may be from two to a maximum length of about 12 Sb2 dimers. We
responsible for the unexpected growth direction and studied find the crossover from single dimer behavior abruptly at the
shortest possible ‘‘Sb line’’ with two dimers where one is
located between the chains of the Si. A two dimer Sb line
already shows the end-state behavior which is consistent
with the reactive sites shown for the four dimer Sb line in
Fig. 1.
The Sb dimer rows preferentially terminate between the
Si chains as shown in Fig. 1 resulting in an odd number of
Sb2 dimers in most of the Sb lines. Apparently this configu-
ration right end in Fig. 1 is more favorable since the next
growth step would require the break of the bond of the Si2
dimer in the next chain which is probably already strained
but not broken. In the empty state image of Fig. 1 some of
the Sb row ends show a rounded feature which seems to
extend the Sb line partly into the next chain of the Si. We
speculate that this may be an impurity atom, terminating the
FIG. 4. The normalized spectrum (dI/dV)/(I/V) showing simi- reactive end of the Sb line.
lar behavior of the center of the Sb line and the clean Si surface. In contrast to Sb lines of two dimers or more a single Sb2
The Sb line end displays a finite LDOS at E F and peaks between E F could be bonded via the orbital of the Si 2 1 reconstruc-
and the Si state. tion leaving the Si dimer bond intact. The alternative is the
4. 15 344 BRIEF REPORTS PRB 62
breakup of the bond even for a free dimer. To our knowl- growth. It is necessary to include the energy gain of bonding
edge this question has not been addressed carefully. Our an additional dimer to the Sb line to explain the extended
spectroscopy data show the similarity of the Sb2 states to the growth.
Si2 orbitals, only 0.2 eV shifted to lower valence energy. In conclusion, we presented spectroscopy data on epitax-
Since we observe states at relative low energy 2 eV this ial Sb nanostructures on Si 001 . The ends of the Sb dimer
suggests that the remaining two electrons per Sb atom are row show a finite density of states at the Fermi level in
not involved in a like bond to the Si leaving the Si-Si contrast to the center of the Sb line which is semiconducting
bond intact. Based on this observation we propose that the with characteristics similar to Si 001 2 1. We found no
Sb2 is chemisorbed by breaking only the bond of the Si2 evidence for the replacement of Si by Sb in the surface. We
dimer. propose that the end state is the experimental evidence for
When a Si 001 surface with Sb2 dimers is annealed at the surface polymerization model.1 The self-assembly of the
sufficiently high temperature we achieved this at approxi- Sb line begins by breaking the bond of the Si and a very
mately 575 K the bond of the Si dimer is definitely reactive site is formed. This site enhances the density of
broken7 and the growth of the Sb dimer row continues until states at E F Fermi level and propagates the surface poly-
it is terminated by strain induced in the Sb line. At lower merization.
temperatures the Sb2 is diffusing on the surface by bonding
to the orbitals. The higher temperature makes it possible to The authors wish to thank T.M. Klapwijk for detailed
break the bond resulting in the reactive ends leading to the discussions concerning this work and J.E. Mooij, S. Rade-
one-dimensional growth discussed here. Considering the ra- laar, and F. Tuinstra for their support. This work was finan-
tio of the covalent radii of Sb and Si, r Sb /r Si 1.21, 14 it is cially supported by the university and the ‘‘Stichting voor
quite remarkable that the epitaxial Sb lines of Sb grow up to Fundamenteel Onderzoek der Materie FOM ’’ which is a
a maximum length of approximately 5 nm considering the subsection of the ‘‘Nederlandse Organisatie voor Weten-
strain of l/l 17% in the Sb line corresponding to ap- schappelijk Onderzoek NWO .’’ S.R. and L.J.G. wish to
proximately two atoms over 5 nm . This shows that the acknowledge financial support from the Royal Netherlands
simple covalent radius model is not sufficient to explain the Academy of Arts and Sciences.
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