This document summarizes a study on the effect of atomic layer deposited (ALD) Al2O3 barrier layers of varying thicknesses on forward electron injection from Ru(dcbpy)2(NCS)2 dye to nanocrystalline TiO2 films. Transient absorption spectroscopy showed that a single ALD cycle producing a 1 Å Al2O3 layer decreased singlet electron injection, while more than two cycles also slowed triplet injection. The findings indicate that Al2O3 barriers suppress total electron injection by weakening electronic coupling between the dye and TiO2 and modifying the TiO2 electronic structure. ALD allows precise control of barrier thickness and uniform coverage, making it superior to sol-gel methods for this application.
Synthesis and characterisation of k doped zno 1Jeslin Mattam
Thin film technology has been developed for integrated circuits. Thin films are two-dimensional due to their small thickness and need a substrate. They are created through atomic/molecular processes like chemical vapor deposition or physical deposition. Structural properties are analyzed using electron diffraction and electrical properties depend on temperature. Optical measurements determine band structure and lattice vibrations. Applications include drug delivery, optical coatings, transistors, solar cells, and metallurgical coatings. Zinc oxide thin films were synthesized with potassium doping and analyzed. X-ray diffraction showed the films were phase pure wurtzite structure. Resistance decreased and particle size increased with higher doping concentration.
Ic technology- diffusion and ion implantationkriticka sharma
The document discusses various methods of doping semiconductors, including diffusion and ion implantation. It provides details on Fick's laws of diffusion and their solutions, which describe how dopant concentration changes over time during diffusion. The effects of temperature, electric fields, and oxidation on diffusion are also covered. Ion implantation is introduced as an alternative doping technique that allows for precise control of dopant dose and depth but requires annealing. Key advantages and challenges of each method are highlighted.
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.
This document discusses dopant diffusion, which is the process of introducing controlled amounts of chemical impurities into a semiconductor lattice. Dopant diffusion is used to form source, drain, base, and emitter regions in semiconductor devices. The document covers various diffusion techniques and parameters, including diffusion sources, solid solubility limits, Fick's laws of diffusion, analytical solutions to the diffusion equations, design of diffused layers, and an example design calculation for a boron diffusion process.
This document presents an overview of a thesis on characterizing an aluminum-doped conductive layer of zinc oxide for thin film solar cells. It discusses preparing the aluminum-doped zinc oxide layer using a sol-gel method, including solution preparation, spin coating, and annealing. It also summarizes methods used to characterize the layer, including measuring thickness, surface morphology, and electrical properties using Hall effect measurement. Key results found the layer thickness and roughness increased with more depositions and the material exhibited n-type conductivity.
A few Curious Aspects of ZnO Nanostructures - Prof.Joy MitraSTS FORUM 2016
This document summarizes research on designing defects in ZnO nanostructures. It discusses how ZnO naturally forms with n-type doping due to oxygen vacancies and zinc interstitials. The researcher investigates controlling the ratio of zinc interstitials to oxygen vacancies to tune the material's optical and electrical properties. Photoluminescence and conductive atomic force microscopy experiments on ZnO nanorods with varying defect concentrations show changes in emission spectra and localized photoresponse correlated with grain structure. The findings provide insight into defect engineering of ZnO for optoelectronic applications.
Zinc oxide nanoparticles based passive saturable absorber for pulse generatio...TELKOMNIKA JOURNAL
A stable passive Q-switched pulsed generation in Erbium doped fiber laser by Zinc Oxide
nanoparticles embedded in polyvinyl alcohol (ZnONP-PVA)-based saturable absorber is demonstrated in this
paper. The surface morphology and thickness profile of the fabricated film were observed using FESEM and
3D measuring laser microscope with the measured thickness of 12 μm. Meanwhile the its optical properties is
characterized using Raman spectroscopy. The developed ZnONP-PVA film, has modulation depth of 7.8%
and intensity saturation of 88.97 MW/cm2. The threshold input pump power to generate Q-switched pulse is
at 45.4 mW and can be tuned until 92.4 mW before the pulse diminished. The operating wavelength of
generated pulse is at 1535 nm with 3 dB bandwidth approximately of 2 nm with exclusion of parasitic
continuous wave lasing. As the input pump power was tuned from threshold to maximum value, the recorded
pulse train of repetition rate is tunable from 73.53 kHz to 103.10 kHz while the pulse width decreases from
6.8 μs to 4.8 μs. The calculated maximum output power and pulse energy at maximum input pump power
was 5.14 mW and 49.85 nJ, respectively. The measured signal to noise ratio was 56 dB indicated that the
generated pulse by ZnO NP based passive saturable absorber was stable.
Synthesis and characterisation of k doped zno 1Jeslin Mattam
Thin film technology has been developed for integrated circuits. Thin films are two-dimensional due to their small thickness and need a substrate. They are created through atomic/molecular processes like chemical vapor deposition or physical deposition. Structural properties are analyzed using electron diffraction and electrical properties depend on temperature. Optical measurements determine band structure and lattice vibrations. Applications include drug delivery, optical coatings, transistors, solar cells, and metallurgical coatings. Zinc oxide thin films were synthesized with potassium doping and analyzed. X-ray diffraction showed the films were phase pure wurtzite structure. Resistance decreased and particle size increased with higher doping concentration.
Ic technology- diffusion and ion implantationkriticka sharma
The document discusses various methods of doping semiconductors, including diffusion and ion implantation. It provides details on Fick's laws of diffusion and their solutions, which describe how dopant concentration changes over time during diffusion. The effects of temperature, electric fields, and oxidation on diffusion are also covered. Ion implantation is introduced as an alternative doping technique that allows for precise control of dopant dose and depth but requires annealing. Key advantages and challenges of each method are highlighted.
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.
This document discusses dopant diffusion, which is the process of introducing controlled amounts of chemical impurities into a semiconductor lattice. Dopant diffusion is used to form source, drain, base, and emitter regions in semiconductor devices. The document covers various diffusion techniques and parameters, including diffusion sources, solid solubility limits, Fick's laws of diffusion, analytical solutions to the diffusion equations, design of diffused layers, and an example design calculation for a boron diffusion process.
This document presents an overview of a thesis on characterizing an aluminum-doped conductive layer of zinc oxide for thin film solar cells. It discusses preparing the aluminum-doped zinc oxide layer using a sol-gel method, including solution preparation, spin coating, and annealing. It also summarizes methods used to characterize the layer, including measuring thickness, surface morphology, and electrical properties using Hall effect measurement. Key results found the layer thickness and roughness increased with more depositions and the material exhibited n-type conductivity.
A few Curious Aspects of ZnO Nanostructures - Prof.Joy MitraSTS FORUM 2016
This document summarizes research on designing defects in ZnO nanostructures. It discusses how ZnO naturally forms with n-type doping due to oxygen vacancies and zinc interstitials. The researcher investigates controlling the ratio of zinc interstitials to oxygen vacancies to tune the material's optical and electrical properties. Photoluminescence and conductive atomic force microscopy experiments on ZnO nanorods with varying defect concentrations show changes in emission spectra and localized photoresponse correlated with grain structure. The findings provide insight into defect engineering of ZnO for optoelectronic applications.
Zinc oxide nanoparticles based passive saturable absorber for pulse generatio...TELKOMNIKA JOURNAL
A stable passive Q-switched pulsed generation in Erbium doped fiber laser by Zinc Oxide
nanoparticles embedded in polyvinyl alcohol (ZnONP-PVA)-based saturable absorber is demonstrated in this
paper. The surface morphology and thickness profile of the fabricated film were observed using FESEM and
3D measuring laser microscope with the measured thickness of 12 μm. Meanwhile the its optical properties is
characterized using Raman spectroscopy. The developed ZnONP-PVA film, has modulation depth of 7.8%
and intensity saturation of 88.97 MW/cm2. The threshold input pump power to generate Q-switched pulse is
at 45.4 mW and can be tuned until 92.4 mW before the pulse diminished. The operating wavelength of
generated pulse is at 1535 nm with 3 dB bandwidth approximately of 2 nm with exclusion of parasitic
continuous wave lasing. As the input pump power was tuned from threshold to maximum value, the recorded
pulse train of repetition rate is tunable from 73.53 kHz to 103.10 kHz while the pulse width decreases from
6.8 μs to 4.8 μs. The calculated maximum output power and pulse energy at maximum input pump power
was 5.14 mW and 49.85 nJ, respectively. The measured signal to noise ratio was 56 dB indicated that the
generated pulse by ZnO NP based passive saturable absorber was stable.
This document discusses ZnO nanostructures and their applications in nano-LEDs and nano-generators. It first provides background on ZnO, including its properties and common forms. It then describes the principles and synthesis methods of flexible nano-LEDs and piezoelectric nano-generators based on ZnO nanowires. Potential applications of these ZnO nanostructure devices include lighting, self-powered nanosystems, portable electronics and alternative energy.
Low Temperature Synthesis of ZnO Nanoparticlescurtistaylor80
This document summarizes a new low-temperature vapor phase transport process for synthesizing ZnO nanoparticles. ZnO powder and carbon are used as precursors and decomposed at temperatures as low as 225°C to form ZnO nanoparticles. Reaction conditions like time, temperature, and gas flow rate can be adjusted to control the nanoparticle size, with smaller sizes exhibiting stronger surface-related photoluminescence. This new method allows for the low-temperature physical synthesis of high-quality ZnO nanoparticles suitable for applications in flexible electronics and optoelectronics.
AVS-62 San jose 2015 ELD Cu NPs Conc IL-V2Lance Hubbard
This document summarizes research on depositing electrostatic copper nanoparticle films. Key points:
1) Copper nanoparticle films can be deposited at low temperatures using an electrostatic coating process with ligandless nanoparticles and an ionic liquid charge compensator.
2) Continuous and conductive copper nanoparticle films form when the ionic liquid concentration is between 2.1-2.4 mM, as this concentration increases interparticle interactions and bulk-like behavior.
3) Ellipsometry analysis shows the films have a polydisperse nanoparticle structure with increased ultraviolet absorption and particle interactions at optimal ionic liquid concentrations.
This document discusses the nonlinear optical properties of copper nanoparticles prepared by pulse laser ablation in different solutions. Copper nanoparticles were synthesized in distilled water, deionized water, and a mixture of ethylene glycol and deionized water using a nanosecond pulsed Nd:YAG laser. Characterization using UV-visible spectroscopy and SEM showed the nanoparticles had surface plasmon resonance peaks between 590-676 nm and diameters ranging from 13.16-21.25 nm depending on the solution. Z-scan measurements determined the nonlinear refractive index and nonlinear absorption coefficient of the copper nanoparticle suspensions.
In-situ TEM studies of tribo-induced bonding modification in near-frictionles...Deepak Rajput
A presentation on "In-situ TEM studies of tribo-induced bonding modification in near-frictionless carbon films" made by Deepak Rajput. This presentation was based on "critical review of a paper," in All Things Carbon course offered at the University of Tennessee Space Insitute at Tullahoma in Fall 2009.
Synthesis And Characterization Of Individual ZnO NanowiresMartial Duchamp
This document summarizes research on synthesizing and characterizing individual zinc oxide (ZnO) nanowires. It describes using a vapor-liquid-solid chemical vapor deposition method to grow ZnO nanowires on various substrates with diameters as small as 40nm. The document discusses controlling nanowire diameter and length, characterizing the nanowires' optical and electrical properties, and measuring their enhanced Young's modulus compared to bulk ZnO. Potential applications for ZnO nanowires include piezoelectric devices, field effect transistors, and nanogenerators.
The document summarizes the synthesis of tungsten disulfide (WS2) nanosheets using chemical vapor deposition (CVD) with a gas-phase sulfur reactant. It is observed that the WS2 grows laterally and that domains coalesce over time. The number of layers can be controlled by adjusting the reaction time. Additionally, a graphene/WS2 heterostructure is shown to have properties suitable for photo detection.
Electrochemical Synthesis of MoO3 Nanoparticles Effect of Temperature Convert...IJERA Editor
MoO3 nanorods were prepared by electrochemical reduction method using the tetra propyl ammonium bromide (TPAB) was structure directing agent in an organic medium viz. tetra hydro furan (THF) and acetonitrile (ACN) in 4:1 ratio and at current density 14mA &18 mA. The reduction process takes place under atmospheric condition over a period of 2 h. Dried sample was calcinated in muffle furnace at 500ºC. The parameters such as current density and concentration of stabilizers were used to control the size of nanorods. The synthesized MoO3 nanorods were characterized by using UV-Visible, FT-IR, XRD, SEM-EDS and TEM analysis techniques.
Interdiffusion, reactions, and transformations in thin filmMd Ataul Mamun
This document discusses various topics related to interdiffusion, reactions, and transformations in thin films:
1. It explains the concepts of diffusion, nucleation and grain growth that can occur in thin films. Diffusion is impacted by factors like temperature, grain boundaries, and dislocations.
2. Interdiffusion in thin films occurs much faster than in bulk materials due to diffusion along grain boundaries and dislocations. This can impact thin film integrity over time.
3. Reaction and compound formation at interfaces between thin films is discussed, like the growth of SiO2 at the Si/O2 interface or intermetallic compound formation.
4. Phase transformations and the use of diffusion barriers to prevent undesirable
Zinc Oxide Nanowires Prepared by Hot Tube Thermal EvaporationSyahida Suhaimi
The document describes a study investigating the effect of substrate tilt angle and argon gas flow rate on the structural properties of zinc oxide nanowires synthesized using a hot tube thermal evaporation method. Zinc oxide nanowires were grown on silicon substrates under different tilt angles (0-30 degrees) and flow rates (1.1-5.0 sccm). The nanowires were characterized using field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The results showed that higher tilt angles and flow rates produced nanowires with improved density, higher aspect ratio, and altered optical properties.
Fabrication and characterization of bismuth ferrite nanofiber by electrospinn...Abthul Hakkeem
This document summarizes a thesis on fabricating and characterizing bismuth ferrite nanofibers using electrospinning. Bismuth ferrite is a multiferroic material with applications in transducers, sensors, and memory. Nanofibers were produced at varying voltages and characterized. X-ray diffraction showed the 10 kV fibers were phase pure while others contained impurities. Scanning electron microscopy found the 10 and 15 kV fibers had the best morphology and size distribution. The thesis evaluated how the applied voltage impacts fiber properties.
The document summarizes a study of the dielectric properties of nano-crystalline Mn-Zn ferrites. Samples of ZnxMn1-xFe2O4 where x ranges from 0.2 to 0.8 were synthesized using a solid-state route and characterized. The ac conductivity σ, dielectric constant ε', dielectric loss ε'', and loss tangent tan δ were measured from 100 Hz to 20 MHz. ε' and ε'' decreased with increasing frequency. σ was nearly frequency independent below 1 MHz and increased sharply above. The maximum dielectric constant and conductivity occurred for x=0.2, attributed to space charge polarization. The conduction mechanism was explained by electron hopping between Fe2+ and Fe
This document describes a project on the formation of PbS thin films using the chemical bath deposition technique. The aims are to deposit PbS thin films using CBD, study the effect of different precursor solutions, and characterize the films using XRD. CBD is described as a low-cost deposition method using controlled chemical reactions. Procedures for depositing PbS films using lead acetate and lead nitrate precursors are provided. XRD results show the films are PbS cubic crystals with grain sizes of 41.9nm and 45.44nm for lead nitrate and acetate, respectively. Conductivity tests show the films are p-type. The effect of varying lead concentration is also studied.
This is a power point presentation of project work on preparing Zinc oxide thin films by using SILAR technique and CBD technique and studying its characteristics.
This document summarizes research on using self-organization phenomena like dewetting and demixing to form nanocrystals. Dewetting of thin films can cause the formation of nanodroplets. Demixing in liquid crystals provides an ordered matrix for nanoparticle growth. Specifically, zinc stearate nanocrystals were formed by dewetting on cadmium and cobalt stearate templates. The nanocrystals had different structures depending on the template. Also, gold nano-prisms were formed in the liquid crystal MBBA using its functional groups to reduce gold salt and provide ordering during demixing. Characterization showed the highly crystalline nature of the nanoparticles.
This document summarizes research on using laser processing techniques to deposit nanocrystalline titanium dioxide (nc-TiO2) films for use in dye-sensitized solar cells. Pulsed laser deposition was used to deposit a dense TiO2 layer and laser direct-write was used to deposit porous nc-TiO2 layers of varying thickness. Solar cells made with laser-processed nc-TiO2 layers showed a power conversion efficiency of up to 4.3% under solar illumination. Thicker nc-TiO2 layers increased short circuit current but decreased open circuit voltage, due to increased recombination losses. Laser processing techniques allow conformal deposition of nc-TiO2 without masks or additional patterning steps.
With the increasing researches in the field of nanotechnology, various nanoparticles have become a source of interest among the nano technologists because of their great properties, like the optical properties of Cadmium Sulfide Nanoparticles are amazing and also easy to synthesize, but to make sure its quality it is equally essential to make out characterize it, this file will do the same in a lucid way!!
A Review of Zinc-Oxide as Nano Materials and Devicesidescitation
This paper presents a review of zinc oxide (ZnO) as
nano material and device. ZnO has gained substantial interest
in the research area of wide band gap semiconductors due to
its unique electrical, optical and structural properties.
Recently, ZnO as nano material generates much interest
among researchers and technologists and have been used in
many devices such as UV photodetectors, light emitting diodes,
solar cells and transistors. Moreover, a brief overview on ZnO
recent advances on nanoparticles, nanowires and their
applications as devices are discussed and reviewed.
This document provides an overview of Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) spectroscopy. It discusses how ATR addresses challenges with traditional transmission FTIR sampling methods, such as difficulties preparing homogeneous solid and liquid samples of a consistent thickness. The document describes how ATR uses an internal reflection element to produce an evanescent wave that interacts with the sample. It explains that ATR provides faster, more reproducible sampling compared to transmission by avoiding issues with sample thickness. Finally, it summarizes that ATR spectroscopy has revolutionized solid and liquid FTIR sampling through improved speed, reproducibility, and consistency between users.
The document discusses the heart and its importance according to the Bible. It provides several Bible verses that reveal the heart as the innermost desire, the source of motivation, and what God looks at directly. It emphasizes that obedience to the gospel, fellowship, and serving others are matters of the heart. Several verses are presented to show how the heart can be deceitful and that God alone knows people's hearts.
20 Ideas for your Website Homepage ContentBarry Feldman
Perplexed about what to put on your website home? Every company deals with this tough challenge. The 20 ideas in this presentation should give you a strong starting point.
This document discusses ZnO nanostructures and their applications in nano-LEDs and nano-generators. It first provides background on ZnO, including its properties and common forms. It then describes the principles and synthesis methods of flexible nano-LEDs and piezoelectric nano-generators based on ZnO nanowires. Potential applications of these ZnO nanostructure devices include lighting, self-powered nanosystems, portable electronics and alternative energy.
Low Temperature Synthesis of ZnO Nanoparticlescurtistaylor80
This document summarizes a new low-temperature vapor phase transport process for synthesizing ZnO nanoparticles. ZnO powder and carbon are used as precursors and decomposed at temperatures as low as 225°C to form ZnO nanoparticles. Reaction conditions like time, temperature, and gas flow rate can be adjusted to control the nanoparticle size, with smaller sizes exhibiting stronger surface-related photoluminescence. This new method allows for the low-temperature physical synthesis of high-quality ZnO nanoparticles suitable for applications in flexible electronics and optoelectronics.
AVS-62 San jose 2015 ELD Cu NPs Conc IL-V2Lance Hubbard
This document summarizes research on depositing electrostatic copper nanoparticle films. Key points:
1) Copper nanoparticle films can be deposited at low temperatures using an electrostatic coating process with ligandless nanoparticles and an ionic liquid charge compensator.
2) Continuous and conductive copper nanoparticle films form when the ionic liquid concentration is between 2.1-2.4 mM, as this concentration increases interparticle interactions and bulk-like behavior.
3) Ellipsometry analysis shows the films have a polydisperse nanoparticle structure with increased ultraviolet absorption and particle interactions at optimal ionic liquid concentrations.
This document discusses the nonlinear optical properties of copper nanoparticles prepared by pulse laser ablation in different solutions. Copper nanoparticles were synthesized in distilled water, deionized water, and a mixture of ethylene glycol and deionized water using a nanosecond pulsed Nd:YAG laser. Characterization using UV-visible spectroscopy and SEM showed the nanoparticles had surface plasmon resonance peaks between 590-676 nm and diameters ranging from 13.16-21.25 nm depending on the solution. Z-scan measurements determined the nonlinear refractive index and nonlinear absorption coefficient of the copper nanoparticle suspensions.
In-situ TEM studies of tribo-induced bonding modification in near-frictionles...Deepak Rajput
A presentation on "In-situ TEM studies of tribo-induced bonding modification in near-frictionless carbon films" made by Deepak Rajput. This presentation was based on "critical review of a paper," in All Things Carbon course offered at the University of Tennessee Space Insitute at Tullahoma in Fall 2009.
Synthesis And Characterization Of Individual ZnO NanowiresMartial Duchamp
This document summarizes research on synthesizing and characterizing individual zinc oxide (ZnO) nanowires. It describes using a vapor-liquid-solid chemical vapor deposition method to grow ZnO nanowires on various substrates with diameters as small as 40nm. The document discusses controlling nanowire diameter and length, characterizing the nanowires' optical and electrical properties, and measuring their enhanced Young's modulus compared to bulk ZnO. Potential applications for ZnO nanowires include piezoelectric devices, field effect transistors, and nanogenerators.
The document summarizes the synthesis of tungsten disulfide (WS2) nanosheets using chemical vapor deposition (CVD) with a gas-phase sulfur reactant. It is observed that the WS2 grows laterally and that domains coalesce over time. The number of layers can be controlled by adjusting the reaction time. Additionally, a graphene/WS2 heterostructure is shown to have properties suitable for photo detection.
Electrochemical Synthesis of MoO3 Nanoparticles Effect of Temperature Convert...IJERA Editor
MoO3 nanorods were prepared by electrochemical reduction method using the tetra propyl ammonium bromide (TPAB) was structure directing agent in an organic medium viz. tetra hydro furan (THF) and acetonitrile (ACN) in 4:1 ratio and at current density 14mA &18 mA. The reduction process takes place under atmospheric condition over a period of 2 h. Dried sample was calcinated in muffle furnace at 500ºC. The parameters such as current density and concentration of stabilizers were used to control the size of nanorods. The synthesized MoO3 nanorods were characterized by using UV-Visible, FT-IR, XRD, SEM-EDS and TEM analysis techniques.
Interdiffusion, reactions, and transformations in thin filmMd Ataul Mamun
This document discusses various topics related to interdiffusion, reactions, and transformations in thin films:
1. It explains the concepts of diffusion, nucleation and grain growth that can occur in thin films. Diffusion is impacted by factors like temperature, grain boundaries, and dislocations.
2. Interdiffusion in thin films occurs much faster than in bulk materials due to diffusion along grain boundaries and dislocations. This can impact thin film integrity over time.
3. Reaction and compound formation at interfaces between thin films is discussed, like the growth of SiO2 at the Si/O2 interface or intermetallic compound formation.
4. Phase transformations and the use of diffusion barriers to prevent undesirable
Zinc Oxide Nanowires Prepared by Hot Tube Thermal EvaporationSyahida Suhaimi
The document describes a study investigating the effect of substrate tilt angle and argon gas flow rate on the structural properties of zinc oxide nanowires synthesized using a hot tube thermal evaporation method. Zinc oxide nanowires were grown on silicon substrates under different tilt angles (0-30 degrees) and flow rates (1.1-5.0 sccm). The nanowires were characterized using field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. The results showed that higher tilt angles and flow rates produced nanowires with improved density, higher aspect ratio, and altered optical properties.
Fabrication and characterization of bismuth ferrite nanofiber by electrospinn...Abthul Hakkeem
This document summarizes a thesis on fabricating and characterizing bismuth ferrite nanofibers using electrospinning. Bismuth ferrite is a multiferroic material with applications in transducers, sensors, and memory. Nanofibers were produced at varying voltages and characterized. X-ray diffraction showed the 10 kV fibers were phase pure while others contained impurities. Scanning electron microscopy found the 10 and 15 kV fibers had the best morphology and size distribution. The thesis evaluated how the applied voltage impacts fiber properties.
The document summarizes a study of the dielectric properties of nano-crystalline Mn-Zn ferrites. Samples of ZnxMn1-xFe2O4 where x ranges from 0.2 to 0.8 were synthesized using a solid-state route and characterized. The ac conductivity σ, dielectric constant ε', dielectric loss ε'', and loss tangent tan δ were measured from 100 Hz to 20 MHz. ε' and ε'' decreased with increasing frequency. σ was nearly frequency independent below 1 MHz and increased sharply above. The maximum dielectric constant and conductivity occurred for x=0.2, attributed to space charge polarization. The conduction mechanism was explained by electron hopping between Fe2+ and Fe
This document describes a project on the formation of PbS thin films using the chemical bath deposition technique. The aims are to deposit PbS thin films using CBD, study the effect of different precursor solutions, and characterize the films using XRD. CBD is described as a low-cost deposition method using controlled chemical reactions. Procedures for depositing PbS films using lead acetate and lead nitrate precursors are provided. XRD results show the films are PbS cubic crystals with grain sizes of 41.9nm and 45.44nm for lead nitrate and acetate, respectively. Conductivity tests show the films are p-type. The effect of varying lead concentration is also studied.
This is a power point presentation of project work on preparing Zinc oxide thin films by using SILAR technique and CBD technique and studying its characteristics.
This document summarizes research on using self-organization phenomena like dewetting and demixing to form nanocrystals. Dewetting of thin films can cause the formation of nanodroplets. Demixing in liquid crystals provides an ordered matrix for nanoparticle growth. Specifically, zinc stearate nanocrystals were formed by dewetting on cadmium and cobalt stearate templates. The nanocrystals had different structures depending on the template. Also, gold nano-prisms were formed in the liquid crystal MBBA using its functional groups to reduce gold salt and provide ordering during demixing. Characterization showed the highly crystalline nature of the nanoparticles.
This document summarizes research on using laser processing techniques to deposit nanocrystalline titanium dioxide (nc-TiO2) films for use in dye-sensitized solar cells. Pulsed laser deposition was used to deposit a dense TiO2 layer and laser direct-write was used to deposit porous nc-TiO2 layers of varying thickness. Solar cells made with laser-processed nc-TiO2 layers showed a power conversion efficiency of up to 4.3% under solar illumination. Thicker nc-TiO2 layers increased short circuit current but decreased open circuit voltage, due to increased recombination losses. Laser processing techniques allow conformal deposition of nc-TiO2 without masks or additional patterning steps.
With the increasing researches in the field of nanotechnology, various nanoparticles have become a source of interest among the nano technologists because of their great properties, like the optical properties of Cadmium Sulfide Nanoparticles are amazing and also easy to synthesize, but to make sure its quality it is equally essential to make out characterize it, this file will do the same in a lucid way!!
A Review of Zinc-Oxide as Nano Materials and Devicesidescitation
This paper presents a review of zinc oxide (ZnO) as
nano material and device. ZnO has gained substantial interest
in the research area of wide band gap semiconductors due to
its unique electrical, optical and structural properties.
Recently, ZnO as nano material generates much interest
among researchers and technologists and have been used in
many devices such as UV photodetectors, light emitting diodes,
solar cells and transistors. Moreover, a brief overview on ZnO
recent advances on nanoparticles, nanowires and their
applications as devices are discussed and reviewed.
This document provides an overview of Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) spectroscopy. It discusses how ATR addresses challenges with traditional transmission FTIR sampling methods, such as difficulties preparing homogeneous solid and liquid samples of a consistent thickness. The document describes how ATR uses an internal reflection element to produce an evanescent wave that interacts with the sample. It explains that ATR provides faster, more reproducible sampling compared to transmission by avoiding issues with sample thickness. Finally, it summarizes that ATR spectroscopy has revolutionized solid and liquid FTIR sampling through improved speed, reproducibility, and consistency between users.
The document discusses the heart and its importance according to the Bible. It provides several Bible verses that reveal the heart as the innermost desire, the source of motivation, and what God looks at directly. It emphasizes that obedience to the gospel, fellowship, and serving others are matters of the heart. Several verses are presented to show how the heart can be deceitful and that God alone knows people's hearts.
20 Ideas for your Website Homepage ContentBarry Feldman
Perplexed about what to put on your website home? Every company deals with this tough challenge. The 20 ideas in this presentation should give you a strong starting point.
This document outlines 50 essential content marketing hacks presented by Matt Heinz, President of Heinz Marketing Inc. at CMWorld. It provides an agenda for the presentation and covers topics such as content planning, measurement, formats, distribution, influencer engagement, repurposing content, and getting sales teams to leverage content. The goal is to provide new tools, tricks and best practices to help convert readers into customers through effective content marketing.
The document discusses prototyping and provides examples of different types of prototypes including paper prototypes, digital prototypes, storyboards, role plays, and space prototypes. It explains that prototyping is used to make ideas tangible and test reactions from users in order to gain insights. Prototypes should be iterated on and fail early to push ideas further and save time and money. Both low and high fidelity prototypes are mentioned as ways to test ideas at different stages of the design process.
10 Insightful Quotes On Designing A Better Customer ExperienceYuan Wang
In an ever-changing landscape of one digital disruption after another, companies and organisations are looking for new ways to understand their target markets and engage them better. Increasingly they invest in user experience (UX) and customer experience design (CX) capabilities by working with a specialist UX agency or developing their own UX lab. Some UX practitioners are touting leaner and faster ways of developing customer-centric products and services, via methodologies such as guerilla research, rapid prototyping and Agile UX. Others seek innovation and fulfilment by spending more time in research, being more inclusive, and designing for social goods.
Experience is more than just an interface. It is a relationship, as well as a series of touch points between your brand and your customer. Here are our top 10 highlights and takeaways from the recent UX Australia conference to help you transform your customer experience design.
For full article, continue reading at https://yump.com.au/10-ways-supercharge-customer-experience-design/
How to Build a Dynamic Social Media PlanPost Planner
Stop guessing and wasting your time on networks and strategies that don’t work!
Join Rebekah Radice and Katie Lance to learn how to optimize your social networks, the best kept secrets for hot content, top time management tools, and much more!
Watch the replay here: bit.ly/socialmedia-plan
http://inarocket.com
Learn BEM fundamentals as fast as possible. What is BEM (Block, element, modifier), BEM syntax, how it works with a real example, etc.
The document discusses how personalization and dynamic content are becoming increasingly important on websites. It notes that 52% of marketers see content personalization as critical and 75% of consumers like it when brands personalize their content. However, personalization can create issues for search engine optimization as dynamic URLs and content are more difficult for search engines to index than static pages. The document provides tips for SEOs to help address these personalization and SEO challenges, such as using static URLs when possible and submitting accurate sitemaps.
ABSTRACT: The direct current photoconductivity of the powdered silicon and photovoltaic effect in the monocrystallic silicon are investigated. It is shown that organic dyes on the semiconductor surface effectively increase the internal photo effect in the dye absorption band. The photoconductivity of dyed powdered samples in the absorption range of the dyes is higher than the photoconductivity of undyed silicon by more than an order of magnitude. The optimum concentration of dye molecules on the monocrystal surface for a sensitization is 3×1015 cm -2 , which corresponds to the dye film thickness of about 30 monolayers or 10-15 nanometers
Optical and Impedance Spectroscopy Study of ZnS NanoparticlesIJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
Seminar on Uv Visible spectroscopy by Amogh G VAmoghGV
PPT of seminar on UV Visible spectroscopy, electronic transitions, Instrumentation of Double beam spectrophotometers, Advantages of Double beam over single beam, Beer Lamberts law derivation
Study the effect of thin film thickness on the optical features of (IR5 laser...TELKOMNIKA JOURNAL
The document studies the effect of thin film thickness and number of laser pulses on the linear and non-linear optical properties of thin film samples composed of IR5 laser dye, CdSe nanoparticles, and polypropylene polymer. Linear properties such as transmittance, absorbance, absorption coefficient, and refractive index were calculated for films of varying thickness and number of laser pulses. Non-linear properties including non-linear refractive index, non-linear phase shift, and non-linear absorption coefficient were determined from Z-scan measurements for films of different thickness. The results show that thicker films eliminate non-linear effects between layers, while CdSe nanoparticles cause absorption shifting to longer wavelengths. Film thickness and number of laser pulses influence non-
The document discusses key concepts related to dye-sensitized solar cells (DSSCs) including light harvesting efficiency, absorption cross section, surface coverage, Langmuir adsorption isotherm, intramolecular charge transfer, and photo-induced electron transfer. Light harvesting efficiency depends on factors like dye surface concentration and extinction coefficient. It can be improved by increasing dye loading, electrode surface area, and light scattering. Absorption cross section and surface coverage are also important for DSSC performance. The Langmuir isotherm model describes dye adsorption, while intramolecular charge transfer and photo-induced electron transfer are important processes in DSSC operation.
This document describes a method for coating metallic surfaces with thin films of nano-dimensional carbon to reduce secondary electron emission and suppress multipactor phenomena. Carbon nano-particles 1-10 nm in size are produced using a multispark discharge in ethyl alcohol. Thin films are then deposited on copper plates via two methods: evaporation of a colloidal solution or electrophoresis. Secondary electron emission measurements found that samples coated with films deposited by evaporation or long-time electrophoresis had lower maximum emission and higher first crossover energy compared to uncoated samples, inhibiting multipactor excitation.
Optical and Electrical Properties of TiO2 Doped Fe2O3 Thin Film Prepared by S...IJAEMSJORNAL
In this work, iron oxide (Fe2O3) and titanium oxide (TiO2) doping (Fe2O3) thin films have been prepared by spray pyrolysis technique (SPT) on a glass substrate. We have studied the effects of various doping percentage of (TiO2) on (Fe2O3) optical and electrical properties. The optical parameters of the prepared films as absorbance, absorption coefficient, optical energy gap and refractive index have been calculated for all prepared films. D.C conductivity and Hall effect for all films are measured. The results showed that absorbance of prepared films decreases with increasing percentage of (TiO2) this lead to increase the energy gap and conductivity decreased with increasing of percentage of (TiO2) as well as the results showed throughout the study that all films have tow activation energy, its value increase with increasing of percentage of (TiO2). Hall effect measurement showed all films have n-type conductivity.
This document discusses various topics related to transmission characteristics of optical fibers, including:
- The main types of losses in optical fibers are attenuation due to absorption and scattering. Absorption includes material absorption from defects, ions, and molecular vibrations. Scattering includes Rayleigh and Mie scattering.
- Other losses include bending losses from micro- and macro-bends, core-cladding losses, and polarization mode dispersion.
- Signal dispersion spreads optical pulses as they propagate and can cause intersymbol interference. The main types are material dispersion, waveguide dispersion, modal dispersion, and polarization mode dispersion.
- Design of single mode fibers aims to optimize parameters like cutoff wavelength, dispersion, mode field diameter
This paper presents a thorough study of the behaviour of microwave absorption occurring in lossy
dielectric slabs as used for microwave absorbers. The influence of the various parameters governing
absorption is demonstrated : dielectric constant, conductivity, thickness of slab and frequency. It is
shown that for several combinations of values for these parameters absorption can be maximized to up
to unity, i.e. all the incident power is absorbed.
PARAMETRIC STUDY OF MICROWAVE ABSORPTION IN LOSSY DIELECTRIC SLABSjmicro
This paper presents a thorough study of the behaviour of microwave absorption occurring in lossy
dielectric slabs as used for microwave absorbers. The influence of the various parameters governing
absorption is demonstrated : dielectric constant, conductivity, thickness of slab and frequency. It is
shown that for several combinations of values for these parameters absorption can be maximized to up
to unity, i.e. all the incident power is absorbed.
Influence of Thickness on Electrical and Structural Properties of Zinc Oxide ...paperpublications3
Abstract: Zinc Oxide (ZnO) thin films were prepared on corning (7059) glass substrates at a thickness of 75.5 and 130.5nm by RF sputtering technique. The deposition was carried out at room temperature after which the samples were annealed in open air at 1500C. The electrical and structural properties of these films were studied. The electrical properties of the films were monitored by four-point probe method while the structural properties were studied by X-ray diffraction (XRD). It was found that the electrical resistance of the films decreases with increase in the thickness of the films. The XRD analysis of the films showed that the films have a peak located at 〖34.31^0-34.35〗^0with hkl (002). Other parameters calculated include the stress ( ) and the grain size (D).
- The document investigates the microwave absorbing properties of composites containing activated carbon fibres (ACFs).
- When the ACF content is 0.76 wt.%, the bandwidth below -10dB is 12.2 GHz, indicating optimal microwave absorption.
- Comparing composites with ACFs and unactivated carbon fibres, activation increases the microwave absorption of the composite by enhancing multiple reflections within the material.
This document summarizes research on photovoltaic structures using thermally evaporated tin sulfide thin films. Key points:
- Tin sulfide films were deposited by thermal evaporation onto glass substrates in thicknesses ranging from 100-300nm.
- The films exhibited n-type conductivity at low thicknesses, transitioning to p-type at higher thicknesses. Bandgaps ranged from 2.1-1.7eV.
- CdS/SnS photovoltaic cells showed open circuit voltages up to 400mV, short circuit current densities up to 0.061mA/cm2, and conversion efficiencies up to 1.49% under 106mW/cm2 illumination.
This to demonstrate the laser ablation of hard materials to form a thin film for optical sensors. The work was done at DIllard University , New Orleans LA by Professor Abdalla Darwish. any comment e-mail adarwish@bellsouth.net.
- The document discusses using a flame synthesis technique called flame stabilization on a rotating surface (FSRS) to produce TiO2 nanoparticles and thin films for use in dye-sensitized solar cells (DSSCs).
- FSRS allows for one-step particle synthesis and film deposition, controlling properties like particle size and crystal phase that impact DSSC efficiency. DSSCs made with FSRS-produced films show efficiencies up to 7.6%.
- Parameters like particle size, crystal phase, thickness, and surface area can be controlled in FSRS and significantly impact DSSC performance. Smaller particles and the anatase crystal phase produce higher photocurrents and efficiencies.
This document summarizes research on the electrodeposition of zinc selenide (ZnSe) thin films at varying deposition periods and pH levels. X-ray diffraction analysis showed the films had a cubic structure. Optical analysis found the band gap decreased from 2.7eV to 1.9eV as pH decreased from 2.1 to 1.8. Transmittance was 46-84% in the visible region and increased slightly with higher pH. Structural analysis via XRD confirmed the preferred orientation was along the (111) plane and lattice constant was 5.667 angstroms.
Transparent Conducting Oxides for Thin Film PVcdtpv
This document summarizes research on transparent conducting oxides (TCOs) for thin film photovoltaics. It discusses TCO properties and applications in different solar cell technologies. Specific materials discussed include ZnO, CdO, and Cd2SnO4. For CdO, it summarizes findings on conductivity, mobility, band structure, and fundamental band gap determination as a function of temperature and carrier concentration. Combinatorial optimization studies of ZnO are also outlined. In general, the document examines TCO physics and materials development to improve thin film solar cell performance and efficiency.
Effect of zinc on structural and some optical properties of cd s thin filmsAlexander Decker
This document summarizes research on the structural and optical properties of cadmium sulfide (CdS) thin films doped with varying concentrations of zinc (Zn). X-ray diffraction analysis showed that all films had a hexagonal structure and were polycrystalline. Grain size decreased with increasing Zn concentration, while surface roughness decreased based on atomic force microscopy. Optical analysis found that transmittance increased with Zn concentration, as did the optical band gap. Increasing the Zn dopant concentration improved some structural and optical properties of the CdS thin films.
This document summarizes the results of a simulation study investigating light absorption in organic solar cells with smooth and pyramidal textured surfaces. The study first optimized a flat organic solar cell structure by simulating the effects of varying each layer's thickness on short-circuit current and quantum efficiency. The optimized flat cell achieved 13.65 mA/cm2 short-circuit current and 84% quantum efficiency at 640 nm. It then proposed a pyramid textured surface to enhance light trapping and absorption compared to a smooth surface. The effects of period and height of the pyramids were analyzed to validate the light trapping model.
1. pubs.acs.org/JPCL
Suppression of Forward Electron Injection from
Ru(dcbpy)2(NCS)2 to Nanocrystalline TiO2 Film
As a Result of an Interfacial Al2O3 Barrier Layer Prepared
with Atomic Layer Deposition
Liisa J. Antila,† Mikko J. Heikkil€,‡ Viivi Aumanen,† Marianna Kemell,‡ Pasi Myllyperkio,†
a €
‡
Markku Leskel€, and Jouko E. I. Korppi-Tommola*
a ,†
†
Department of Chemistry, Nanoscience Center, P.O. Box 35, 40014 University of Jyv€skyl€, Finland and
a a
‡
Laboratory of Inorganic Chemistry, Department of Chemistry, P.O. Box 55, 00014 University of Helsinki, Finland
ABSTRACT Subnanometer-thick Al2O3 barrier layers on nanocrystalline TiO2
film were prepared with atomic layer deposition (ALD). The method allowed
variation of barrier thicknesses at atomic resolution also deep in nanoporous
structures, which makes it a superior method as compared to, e.g., sol-gel
techniques. In this letter we present results on the effect of Al2O3 barriers of
various thicknesses on forward electron injection in dye-sensitized solar cells. A
decrease in the amplitude of the oxidized Ru(dcbpy)2(NCS)2 dye absorption signal
due to singlet injection was observed already after one deposition cycle that
produces a discontinuous layer with nominal thickness of 1 Å. More than two
layer coatings also slowed down the triplet injection. The findings indicate
suppression of total electron injection, which is probably due to the Al2O3-induced
weakening of electronic coupling between the dye and TiO2 as well as modification
of the TiO2 electronic structure.
SECTION Kinetics, Spectroscopy
E
lectron transfer from the excited state of ruthenium have been studied as potential barrier materials, e.g.,
complex dye (Ru(dcbpy)2(NCS)2, also called RuN3, Al2O3,8-12,14 ZrO2,8 SiO2,8 and ZnO.13 While the effect of
dcbpy = 4,40 -dicarboxy-2,20 -bipyridine1) to the con- these materials on recombination rates and power conver-
duction band of the semiconductor (TiO2) is one of the key sion efficiency of the DSSC has been extensively studied, few
processes determining the current output from dye-sensitized reports on their effect on forward electron injection rates
solar cells (DSSCs).2 After excitation the RuN3 singlet state exist.14
undergoes ultrafast electron injection to the semiconductor In liquid-phase methods (the primary methods applied to
(∼50 fs) and intersystem crossing (∼70 fs) to triplet state Al2O3 layer preparation in DSSC, e.g., surface sol-gel
localized on the bipyridine ligands of the RuN3 molecule.3-5 processes15), incomplete penetration of the solution to the
The injection from the triplet state is a heterogeneous process nanoporous TiO2 film results in an uneven coverage of the
occurring on a picosecond time scale.6 The excited state nanosized cavities of the semiconductor.14 Chemical vapor
absorption of the dye attached on TiO2 occurs in the wave- phase methods, such as atomic layer deposition (ALD),16,20
length region of 630-760 nm and that of oxidized dye occurs allow the reactants to penetrate even the most distant nano-
from 760 to 940 nm with correlated time evolution, which is pores near the interface between the semiconductor film and
indicative of a reactant-to-product reaction.4,7 The oxidized the conducting layer of the substrate11 as was found in a
dye absorption dominates over triplet state absorption at Rutherford back-scattering (RBS) measurement of a 8 nm
860 nm as evidenced by an isosbestic point in the excited thick ALD-Al2O3 film on nanoporous TiO2 (data not shown).
state absorption signal of RuN3 dye in solution at this wave- ALD is based on sequential surface reactions where precur-
length. Thus, 860 nm is an ideal probe wavelength for sors react with the surface in a saturative manner. This allows
oxidized dye formation. production of smooth, continuous films and straightforward
Recombination reactions of the injected electron with the control of the thickness of the deposited film by adjusting the
oxidizing agent of the electrolyte (I3-) limit the photocurrent
of the DSSC. As an effort to suppress recombination, the
nanocrystalline semiconductor film has been coated with Received Date: November 23, 2009
high band gap metal oxide layers, which act as barriers for Accepted Date: December 21, 2009
the interfacial electron transfer. Several metal oxide materials Published on Web Date: December 29, 2009
r 2009 American Chemical Society 536 DOI: 10.1021/jz9003075 |J. Phys. Chem. Lett. 2010, 1, 536–539
2. pubs.acs.org/JPCL
number of reaction cycles. In the TMA/H2O process20 used in ∼25% is due to the excited state absorption remaining after
this work, the growth per cycle is ∼1 Å. As a result of the singlet injection.4,17 It is obvious from Figure 1 that the signal
saturative nature of ALD, surface reactions allow rather reli- amplitude in the time domain τ >1 ps up to 200 ps also
able calculation of layer thicknesses from growth per cycle diminishes as the barrier thickness increases, leading to a
(see Supporting Information). For submonolayer films, i.e., decrease in the quantum yield of triplet injection as well.3,4
films deposited with less than five deposition cycles, only Vibrational relaxation of related ruthenium complexes has
nominal thicknesses can be estimated since the submono- been reported to take place in a few picoseconds,18 and these
layer films are discontinuous. To our knowledge, ALD has processes may well compete with the slow injection channel.
been applied to barrier layer preparation in DSSCs only in a The quantum yield of the total electron injection can be
few cases.10-12 We report the first study of the effect of ALD determined by calculating the contribution of the oxidized
Al2O3 barrier layers on the forward electron injection from dye to the total signal from the data in Figure 1 according to14
RuN3 dye to the conduction band of TiO2 as a function of
barrier thickness by femtosecond transient absorption spec- Sð860 nm, tÞ ¼ Nex ðtÞAex ð860 nm, tÞ þ Nox ðtÞAox ð860 nmÞ
troscopy. ð1Þ
All samples were sensitized to the same optical density
(absorbance) 0.5 OD. This allows us to compare the ampli- where S(860 nm, t) is the measured signal at time t and at the
tudes of the transient absorption signals directly. In Figure 1, given wavelength and Nex(t) and Nox(t) represent the relative
signals from excited state absorption of the dye and absorp- populations of the excited state and the oxidized form of the
tion of the oxidized dye are shown in two time domains. In dye, respectively. Aex(860 nm, t) is the time-dependent
the region of singlet injection (τ < 1 ps), the signal amplitude absorption of the excited state, i.e., that of the RuN3/Al2O3
decreases as the barrier thickness increases.3,4 The smaller sample, and Aox(860 nm) is the absorption of the oxidized dye
the amplitude (Table 1) the smaller the oxidized dye number determined from the RuN3/TiO2 signal at 520 ps, i.e., after
density in the excitation volume after excitation. This de- injection has completed. For the excited state, a time-depen-
crease in amplitude implies suppression of the fast electron dent absorption signal is used because of the small decay due
injection from the singlet state of the dye. The oxidized to vibrational energy relaxation, while a constant value can be
dye absorption accounts for ∼75% of the amplitude of the used for the oxidized dye because it has no significant time
transient absorption signal in this spectral range, and the dependence. The amplitude of the oxidized dye signal directly
represents the quantum yield of electron injection, and from
Figure 2 it can be seen that the quantum yield decreases by
15% after the first deposition cycle of Al2O3 and falls 70%
with five deposition cycles, i.e., a monolayer of Al2O3.
The electron injection from the dye to the semiconductor
follows the classical Marcus electron transfer theory in the
nonadiabatic limit. The slowing down of injection as electro-
nic coupling between the dye and the semiconductor weak-
ens has been demonstrated by Asbury et al.19 with the
introduction of CH2 spacer groups between the bipyridine
and the semiconductor binding carboxylate groups. The Al2O3
barrier layer also increases the distance between the electron
donating bipyridine orbitals of the dye and the conduction
band of TiO2, leading to weaker electronic coupling. The
gradual decrease of the transient absorption amplitude
(Figure 1) may be due to the discontinuous nature of the
layers prepared with less than five deposition cycles (<5 Å
Figure 1. Time dependencies of the absorbance changes (in nominal thickness).20 It is possible that some dye molecules
mOD) of excited state of the RuN3 dye and of the oxidized dye are still able to bind to TiO2 in samples where the barrier is
probed at 860 nm after 540 nm excitation on uncoated TiO2, on
TiO2 with Al2O3 barrier layers, and on Al2O3. Solid lines are prepared with one or two deposition cycles, and these con-
exponential fits to the experimental data (symbols). sequently have stronger average electronic coupling than
Table 1. Oxidized Dye Formation Time Constants (τ) and Relative Amplitudes (In Percentages of the Total Amplitude) on Bare TiO2 and
Al2O3 Films and Al2O3-Coated TiO2 Films Obtained from Fitting the Data in Figure 1a
TiO2 1 cycle of Al2O3 2 cycles of Al2O3 3 cycles of Al2O3 5 cycles of Al2O3 Al2O3
instrument limited rise 68% 71% 70% 80% 91% 100%
τ1 (ps) 1.2 ( 0.1 (-11%) 1.2 ( 0.1 (-10) 1.2 ( 0.1 (-10%) 3.9 ( 0.4 (-11%) 26 ( 3 (-9%) 25 ( 3 (19%)
τ2 (ps) 11.0 ( 1.1 (-3%) 11.0 ( 1.1 (-8%) 11.0 ( 1.1 (-7%) 145 ( 15 (-9%)
τ3 (ps) 95 ( 10 (-18%) 95 ( 10 (-10%) 95 ( 10 (-13%)
a
Time resolution of the present experiment did not allow resolving the fast singlet injection rate, which is buried under the instrument limited rise.3,4
Decay amplitudes are given in parentheses.
r 2009 American Chemical Society 537 DOI: 10.1021/jz9003075 |J. Phys. Chem. Lett. 2010, 1, 536–539
3. pubs.acs.org/JPCL
In conclusion, we have shown already that one ALD cycle
of Al2O3 results in a barrier that slows down electron injection
from the singlet excited state of RuN3 dye and decreases the
overall injection efficiency. With more than three ALD cycles
of Al2O3, the triplet state injection is also suppressed, indicat-
ing a shift in the TiO2 density of states.
SUPPORTING INFORMATION AVAILABLE TiO2 thin film
preparation, ALD of Al2O3 barrier layers, sensitization with RuN3,
and time-resolved transient absorption spectroscopy (PDF).
This material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author:
Figure 2. Injection yields calculated using eq 1 from the data in *To whom correspondence should be addressed. E-mail: jouko.
Figure 1. The numbers are total electron injection yields relative to korppi-tommola@jyu.fi.
RuN3/TiO2.
samples where the dye binds only to Al2O3. If the dye is ACKNOWLEDGMENT Support from the FinNano research
unable to bind to TiO2 even after one deposition cycle, then program of the Academy of Finland (Contract Nos. 117969 and
the increasing distance with increasing number of deposition 118040) is acknowledged. L.A. is grateful for support from the
cycles would explain the gradual change in electronic cou- Graduate School of Computational Chemistry and Molecular
pling and the observed amplitude. A more detailed study of Spectroscopy and acknowledges Ph.D. Jani Kallioinen for helpful
the slowing down of electron transfer as a function of barrier discussions. Ph.D. Timo Sajavaara is gratefully acknowledged for
layer thickness will be presented elsewhere. RBS measurements.
The injection kinetics on a picosecond time scale of the
samples with one and two cycles of Al2O3 are almost identical
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