This research article investigates the surface roughness and electrical conductivity of ultra-thin tin dioxide (SnO2) layers deposited by spray pyrolysis. Two sets of samples with different precursor concentrations and volumes were analyzed using X-ray reflectivity. XRR analysis revealed that increasing the precursor volume led to thicker layers with higher electron densities. Higher precursor concentration resulted in denser layers with larger thicknesses. Sheet resistance measurements showed lower values for thicker layers, correlated with their higher electron densities from XRR analysis.
Optical characterization of Se90S10-xCdx thin filmsIOSR Journals
Thin films of different thicknesses of Se90S10-xCdx, (x=0 and 5) were deposited by thermal evaporation technique onto glass substrates. X-ray diffraction patterns (XRD), differential thermal analysis (DTA) and energy dispersive X-ray spectroscopy (EDX) studies were carried out for samples in powder and thin film forms. XRD indicates that all the deposited thin films have an amorphous structure. The transmittance at normal incidence for these films was measured in the wavelength range 350–2500 nm. Applying Swanepoel's method successfully enabled to determine, with high accuracy, the film thickness, the real index of refraction and imaginary part of index of refraction. Regarding the optical absorption measurements; the type of optical transition and optical band gap were estimated as a function of photon energy. The effect of Cd addition on the refractive index, absorption coefficient and the optical band gap were investigated. The high frequency dielectric constant, the single oscillator energy, the dispersion energy and refractive index dispersion parameter were evaluated. Solar cell criterions have been considered. The results are interpreted in terms of concentration of localized states.
Optical characterization of Se90S10-xCdx thin filmsIOSR Journals
Thin films of different thicknesses of Se90S10-xCdx, (x=0 and 5) were deposited by thermal evaporation technique onto glass substrates. X-ray diffraction patterns (XRD), differential thermal analysis (DTA) and energy dispersive X-ray spectroscopy (EDX) studies were carried out for samples in powder and thin film forms. XRD indicates that all the deposited thin films have an amorphous structure. The transmittance at normal incidence for these films was measured in the wavelength range 350–2500 nm. Applying Swanepoel's method successfully enabled to determine, with high accuracy, the film thickness, the real index of refraction and imaginary part of index of refraction. Regarding the optical absorption measurements; the type of optical transition and optical band gap were estimated as a function of photon energy. The effect of Cd addition on the refractive index, absorption coefficient and the optical band gap were investigated. The high frequency dielectric constant, the single oscillator energy, the dispersion energy and refractive index dispersion parameter were evaluated. Solar cell criterions have been considered. The results are interpreted in terms of concentration of localized states.
A Study of Pulse by Pulse Microscale Patch Transfer Using Picosecond LaserIJERA Editor
The shape restoring capability of Ti/Ni has potential to overcome the shrinkage of polymer in mould cavity, which has potential of solving the demoulding problems and helps dimension accuracy in micro/nano injection molding. However, the deposition of Ti/Ni film precisely and securely on specific location of the micro mould cavity present difficulties with conventional deposition methods. In this paper, the use of photonic impact forward transfer method to deposit Ti/Ni film patches on specific locations of a substrate is demonstrate using a picosecond laser. Pulse by pulse deposition control parameters affecting position accuracy and spot size were studied in this paper. It was found that although laser power, and distance between donor films and the substrate all influence the spot sizes of pulse by pulse deposited patches, adjusting spot size by changing laser power is better than changing distance due to separated particles being found around the deposited film patches. Results of this study proved the feasibility of depositing Ti/Ni film patches on specific location using pico-second laser with high position accuracy. The potential of using photonic impact forward transfer as a complementing method to laser powder 3D printing of difficult to process material to produce better surface quality microproducts such as micro moulds for micro-injection molding is tremendous.
Invited lecture of the Simposium N "Surface Engineering - functional coatings and modified surfaces" at the XIII SBPMat (Brazilian MRS) meeting, in João Pessoa (Brazil). The lecture took place on September 30th, 2014.
The speaker was Professor Christoph Genzel, from the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), in Germany, where he heads the Department of Microstructure and Residual Stress Analysis and he coordinates a group of diffraction and scattering. Genzel is also Associate Professor at the Technische Universität Berlin.
Effect of Sn Doping on Structural and Electrical Properties of ZnO Thin Films...journal ijrtem
Abstract: Un-doped and tin (Sn) doped ZnO films were deposited on heated glass substrates by chemical spray pyrolysis method
(CSP). The effect of Sn concentration on the structural, surface morphological and electrical properties of the SnO2 films was
investigated. XRD analyses showed that the obtained films are polycrystalline in nature with hexagonal structure with preferred
orientation of (101). Doping with tin (Sn) causes increase in the grain size. Atomic force microscopy images showed that the root
mean square of the average surface roughness's varied from (1.48 to 3.58) as dopant concentration increased from 0 to 5 wt.%. The
electrical properties of the Sn ZnO films were strongly influenced by doping concentration. The electrical resistance of the films was
sharply decreased as dopant concentration increased.
Keywords: (ZnO) thin films, Sn Doping, Structural and electrical Properties
Abstract
Terahertz spectral analysis has been conducted on epitaxially grown semiconductor structures. Epitaxially grown semiconductors are important for microelectronic and optoelectronic devices and also for integrated circuits
fabricated using semiconductors. In this paper, we report results of terahertz time-domain spectroscopy of grown
SiGe layers on Ge buffer and separately a Ge buffer that was grown on a Si <001> wafer. In particular, evolution of
the time-domain spectra as a function of thickness of both samples was investigated by the terahertz pump-probe
technique. Representative spectra were analyzed to determine the respective layers’ spectral signatures. It was found that the spectroscopic analysis uniquely identified different layers by characteristic absorbance peaks. In addition, terahertz imaging was conducted in a non-destructive, non-contact mode for detecting lattice stacking fault and dislocations. Sub-surface imaging of grown SiGe layers on Ge buffer and that of the Ge buffer grown on a Si wafer reveals interesting lattice features in both samples. A comparison with TEM images of the samples exhibits that the terahertz image reproduces the dimensions found from TEM images within the experimental error limits. In particular, 3D images of both samples were generated by the terahertz reconstructive technique. The images were analyzed by graphical means to determine the respective layer thicknesses. Thus, this technique offers a versatile tool for both semiconductor research and in-line inspections.
A Study of Pulse by Pulse Microscale Patch Transfer Using Picosecond LaserIJERA Editor
The shape restoring capability of Ti/Ni has potential to overcome the shrinkage of polymer in mould cavity, which has potential of solving the demoulding problems and helps dimension accuracy in micro/nano injection molding. However, the deposition of Ti/Ni film precisely and securely on specific location of the micro mould cavity present difficulties with conventional deposition methods. In this paper, the use of photonic impact forward transfer method to deposit Ti/Ni film patches on specific locations of a substrate is demonstrate using a picosecond laser. Pulse by pulse deposition control parameters affecting position accuracy and spot size were studied in this paper. It was found that although laser power, and distance between donor films and the substrate all influence the spot sizes of pulse by pulse deposited patches, adjusting spot size by changing laser power is better than changing distance due to separated particles being found around the deposited film patches. Results of this study proved the feasibility of depositing Ti/Ni film patches on specific location using pico-second laser with high position accuracy. The potential of using photonic impact forward transfer as a complementing method to laser powder 3D printing of difficult to process material to produce better surface quality microproducts such as micro moulds for micro-injection molding is tremendous.
Invited lecture of the Simposium N "Surface Engineering - functional coatings and modified surfaces" at the XIII SBPMat (Brazilian MRS) meeting, in João Pessoa (Brazil). The lecture took place on September 30th, 2014.
The speaker was Professor Christoph Genzel, from the Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), in Germany, where he heads the Department of Microstructure and Residual Stress Analysis and he coordinates a group of diffraction and scattering. Genzel is also Associate Professor at the Technische Universität Berlin.
Effect of Sn Doping on Structural and Electrical Properties of ZnO Thin Films...journal ijrtem
Abstract: Un-doped and tin (Sn) doped ZnO films were deposited on heated glass substrates by chemical spray pyrolysis method
(CSP). The effect of Sn concentration on the structural, surface morphological and electrical properties of the SnO2 films was
investigated. XRD analyses showed that the obtained films are polycrystalline in nature with hexagonal structure with preferred
orientation of (101). Doping with tin (Sn) causes increase in the grain size. Atomic force microscopy images showed that the root
mean square of the average surface roughness's varied from (1.48 to 3.58) as dopant concentration increased from 0 to 5 wt.%. The
electrical properties of the Sn ZnO films were strongly influenced by doping concentration. The electrical resistance of the films was
sharply decreased as dopant concentration increased.
Keywords: (ZnO) thin films, Sn Doping, Structural and electrical Properties
Abstract
Terahertz spectral analysis has been conducted on epitaxially grown semiconductor structures. Epitaxially grown semiconductors are important for microelectronic and optoelectronic devices and also for integrated circuits
fabricated using semiconductors. In this paper, we report results of terahertz time-domain spectroscopy of grown
SiGe layers on Ge buffer and separately a Ge buffer that was grown on a Si <001> wafer. In particular, evolution of
the time-domain spectra as a function of thickness of both samples was investigated by the terahertz pump-probe
technique. Representative spectra were analyzed to determine the respective layers’ spectral signatures. It was found that the spectroscopic analysis uniquely identified different layers by characteristic absorbance peaks. In addition, terahertz imaging was conducted in a non-destructive, non-contact mode for detecting lattice stacking fault and dislocations. Sub-surface imaging of grown SiGe layers on Ge buffer and that of the Ge buffer grown on a Si wafer reveals interesting lattice features in both samples. A comparison with TEM images of the samples exhibits that the terahertz image reproduces the dimensions found from TEM images within the experimental error limits. In particular, 3D images of both samples were generated by the terahertz reconstructive technique. The images were analyzed by graphical means to determine the respective layer thicknesses. Thus, this technique offers a versatile tool for both semiconductor research and in-line inspections.
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.
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.
Copper indium sulphide films were deposited by the
pulse plating technique with different OFF times in the range of
5s – 30s and at a constant current density of 5 mA cm-2. The
films exhibited single phase copper indium sulphide. The grain
size increased with decrease of OFF time. Optical band gap of the
films increased from 1.44– 1.497 eV with decrease of OFF time.
Optical constants (refractive index, n, and extinction co-efficient,
k) of the films have been obtained in the wavelength range 800 -
1700 nm by using spectrophotometric measurement. The
obtained results concerning the absorption index yield the energy
gap in addition to the type of the allowed optical transitions.
N/m* ratio has been obtained from refractive index data. The
dispersion of refractive index is analyzed by using a single
oscillator model.
Synthesis and Characterization of CuS/PVA Nanocomposite via Chemical method iosrjce
Nanocomposite of copper sulfide (CuS /PVA) have been synthesized according to chemical
precipitation method at temperature 65ºC by simple reaction between copper acetate (Cu (ac)) and thiourea
(H2NCSNH2) at pH=9. Polyvinyl Alcohol (PVA), used as capping agent, was found to play a key role in the
confinement process.
The characterization of the product was done by UV-VIS spectroscopy, atomic force microscopy
(AFM) and x-ray diffraction (XRD). The X-ray diffraction showed the covellite phase of copper sulphides with
hexagonal crystal structure. The sizes of the sample as prepared were calculated by Debye-Scherrer formula
according to XRD spectra. A UV-VIS optical spectroscopy study was carried out to determine the band gap of
the nanocomposite CuS to be about 3.3 eV
A Front Surface Optimization Study for Photovoltaic ApplicationTELKOMNIKA JOURNAL
In this paper, we presented a possible front surface optical enhancement of Si solar cell by
optimizing the Antireflection (AR) and light trapping (LT) schemes. Conventional plasma enhanced
chemical vapor deposition (PECVD) and in house hot wire chemical vapor deposition (HWCVD) tool was
used to deposit Silicon Nitride (SiNX) layer and optimized at 668nm wavelength. This was followed by
surface texturing of random pyramids to further enhance the broadband reflectance of the front surface.
Broadband reflectance measurement using integrating sphere method showed achieved weighted average
reflectance (WAR) value of as low as 1.8% and 1.5%, when 85nm SiNX was deposited on top of random
pyramids structure using HWCVD and PECVD methods, respectively.
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.
Study the effect of thin film thickness on the optical features of (IR5 laser...TELKOMNIKA JOURNAL
The linear optical features such as (transmittance T, absorbance A, the effective length 퐿푒푓푓, absorption coefficient 훼 and refractive index 푛 ) for the thin films samples of (3x10-3 mol/l of (IR5) laser dye, 0.02 gm of (CdS) nanoparticles and 0.04 gm of pp polymer) had been studied at different values of film thickness in one time and at different number of Yb:GdVO4 laser pulses. The non-linear optical features in terms of transmittance difference Δ푇푝−푣, non-linear refractive index 푛2, non–linear phase shift Δ훷표 non-linear absorption coefficient 훽 and minimum normalized transmittance 푇(푍) have been computed in relation to obtained normalized transmittance data from setup of Z-scan with open and closed apertures, calculated for (3x10-3 mol/l of (IR5) laser dye, 0.02 gm of (CdSe) nanoparticles and 0.04 gm of (pp) polymer) thin films at different values of film thickness at in one time and at different Yb:GdVO4 laser pulses. Thick films causes in deleting the non-linear effects generated by different layers. The (CdSe) nanoparticles leads to an absorption shifting of the wavelengths to lengthier wavelengths of red shift. So, this can be used in selecting the nanoparticles and medium with applicable exciting wavelengths. The film thickness and the laser pulses have the main effects in consolidating the Non-linear optical features.
Morphological and Optical Study of Sol-Gel SpinCoated Nanostructured CdSThin ...iosrjce
Nanostructured CdS thin films of different thicknesses were deposited on a cleaned glass substrate
using sol-gel spin coating technique. CdS thin films were prepared using cadmium acetate as cadmium source
and thiourea as sulfur source. The Morphological, chemical composition, and optical properties of the spin- coated
CdS thin film were studied using field emission- scanning electron microscopy (FE-SEM), Energy dispersive X –ray
(EDX) spectroscopy, and a UV-Vis-NIR spectrophotometer.The morphological results revealed that the films consist
of agglomerated spherical CdS nanoparticles with diameter < 20 nm, which distributed uniformly on the substrate
surface.The films show high transmittance > 90% and very strong absorption edge at 295 nm.The absorption edge
shifts towards longer wavelength as the film thickness increased.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
2. layers with subnanometer resolution. However, due to the loss of
phase information in the process, analysis of the XRR data will be
model dependent.
In the present article, our objective is to obtain an electron
density profile (EDP), thickness, and roughness of the nanostructured
ultra-thin films prepared by spray pyrolysis method. The effect of
precursor volume (PV) and PC on the thin film structures will be inves-
tigated by considering their XRR curves. The sheet resistance of the
samples was measured by the four-probe method, and the results
were interpreted concerning the corresponding EDPs deduced from
XRR data.
2 | EXPERIMENTAL SECTION
Two sets of samples were prepared and considered. The first set
includes four samples (named A–D) with PV of varying from 20 to
50 mL with an increment of 10 mL. In this set, PC is 0.01 M. The
second set includes samples (named–H) with the same PV condition
as the first set but possessing a higher PC = 0.05 M. To produce a pre-
cursor solution, SnCl2 2H2O was dissolved in 3 mL of concentrated
hydrochloric (HCl) acid. The resultant transparent solution was then
diluted with methanol to form 0.01 M (Set 1) and 0.05 M (Set 2)
starting precursor solutions. In this study, the precursor solutions used
to spray perpendicularly onto the substrates of microscopic glass
slides (75 × 25 × 1.4 mm3
). The substrates were cleaned using
deionized distilled water and various organic solvents. The tempera-
ture of the substrates was kept at 450
C. The compressed ambient air
supplied by an air compressor was utilized to atomize the solution.
The carrier gas (air) flow rate was maintained at 3 mL/min at a
pressure of 1 atm. The distance between the spray nozzle and the
substrate is fixed at 40 cm.
In this work, a model consisting of layers of constant electron
density was utilized for which the Vidal and Vincent matrix model12
can be employed. A model to describe the EDP of the deposited
layers using complementary error function at the interfaces of
substrate-film and film-vacuum was presented:
ρ z
ð Þ =
1
2
X
i
δρ z
ð Þerfc
z−zi
ffiffiffi
2
p
σi
, ð1Þ
where δρ(z) is the electron density difference between two adjacent
layers and σi is the root mean square roughness of the interface i.
A high-resolution diffractometer, with a copper X-ray tube
(λ = 1.54 Å) at the Physics Department of McGill University, Montreal,
Quebec, Canada, is used to take the XRR data. In this setup, two
germanium crystals acting as analyzer and monochromator with a
3 × 10−5
rad width for their (111) reflection are used. At each detec-
tor position (each 2θ), a θ-rocking scan around ω = 0 (θ = 2θ
2 Þ was done
and then the diffuse part of the scattering was separated (Figure 1).
The remaining specular part can be approximated by a Gaussian curve,
where an average diffuse background line was approximated (insets in
Figure 1) and subtracted from each point in the specular-θ-rocking
curve. Finally, the surface area under the obtained curve is calculated
to give the specular intensity. The crystallographic nature of SnO2 thin
films was studied by the X-ray diffraction (XRD) technique using
Cu-Kα target (λ = 1.54 Å) utilizing X-Pert Pro X-ray diffractometer.
3 | RESULTS AND DISCUSSION
3.1 | XRD analysis
Figure 2 demonstrates the XRD pattern of the SnO2 thin films for
samples in Set 2 with various PVs along with the standard profile of
SnO2 generated from a space group analysis.13
The presence of the
main diffraction peaks in the sample with 50 mL of PV is assigned to
the miller indices of (110) and (101). Two small peaks that happened
at 2θ = 26.60
, for PV = 30 and 40 mL, are indications of a small
FIGURE 1 The θ-rocking curves at 2θ = 1
for 20-, 30-, 40-, and
50-mL samples (first set). The insets illustrate a Gaussian fit (black
line) for the specular parts, and the arrows point the background line
2 ASGHARIZADEH ET AL.
3. percentage of crystallites of (110) Bragg reflection. The XRD pattern
of the samples in Set 1 resembles the ones in Set 2 with no peaks and
are not shown. Using the Scherrer equation, D = 0:9λ
βcosθ , the crystallite
size of the deposited layer was calculated. In the formula, λ is the
X-ray wavelength, β is the full width at half maximum (FWHM) of the
(110) reflection peak in radian, and θ is the Bragg's angle. The
calculated crystallite size was 44.6 nm. It will be discussed in the next
paragraphs that increasing the PV will lead to thicker samples in the
deposition process. As the film thickness increases, the crystallinity of
the film is also improved. This is due to the fact that in the thicker
samples, compared with the thinner ones, small size crystallites have
more chance to agglomerate and coalesce together to enhance the
crystallite structure.
3.2 | XRR analysis
Figure 3A depicts the measured experimental XRR curves (hallow
dots) for samples within Set 1 and the best theoretical fits (solid lines).
In this figure, the intensity of the reflected beam is shown versus
momentum transferred to the film in the direction perpendicular to
the film surface qz = 4π
λ sinθ: The corresponding EDPs are shown in
Figure 3B. In the model presented, each interface is described via a
complementary error function, so a Gaussian profile for dρ/dz at the
interfaces is expected. The XRR curve of the bare substrates was
measured, and root mean square roughness of 5–9 Å was obtained.
From the same curve, the electron density of the glass substrates is
calculated to be 0.71 e/Å3
. The parameters obtained by fitting XRR
curves for Set 1 of the samples are summarized in Table 1. The EDPs
are featured with a plateau region corresponding to the layer density
and two sigmoid-like shapes at the interfaces. For sample A, the root
mean square surface roughness is comparable with the surface rough-
ness of the substrate, indicating that the overlayer partially replicates
the structure of the underlying interface. In samples B and C, it is dis-
cernible that the thickness is doubled compared with sample A, while
the electron density increase is not palpable. As such, one could
accentuate that the effect of the PV change on layer thickness is by
far pronounced than that on the layer density. The XRR curve of
FIGURE 2 XRD pattern of the second set of the samples
FIGURE 3 A, X-ray specular
reflectivity of the first sample set (hollow
dots) and their theoretical fits (solid lines).
The PC = 0.01 M, and the PV = 20,
30, 40, and 50 mL for samples A–D,
respectively. B, Electron density profile of
the samples in Set 1
ASGHARIZADEH ET AL. 3
4. sample D, in Figure 3A, reveals more fringes and higher amplitude of
the oscillations. The larger oscillation amplitude is associated with a
higher electron density contrast between the layer and substrate.
Besides, the presence of more interference modes of electromagnetic
waves in the layer could be attributed to the relatively big thickness
of the layer. At the same time, a big root mean square of surface
roughness deduced from the XRR data fitting (see Table 1) implies a
noticeable specular intensity diminishing in the XRR curve for this
sample. It also appears that the oscillation amplitudes are smeared out
for large qzs, due to the large surface roughness. In this set of samples,
increasing the PV to 50 mL doubles the thickness compared with the
samples B and C (Table 1 and Figure 3B).
Figure 4 illustrates the evolution of the layer thickness and den-
sity as a function of PV for the four samples within the same frame.
While the thickness reaches to as fourfold as its initial value, the layer
density only shows an almost 12% growth.
Figure 5A depicts XRR curves and their theoretical fits of samples
E and F. As seen, the reflectivity curve of sample F goes down faster,
at large values of scattering vectors, compared with sample E. This
indicates that the surface roughness of sample F is higher than that of
sample E.
The calculated surface roughness for samples E and F are 25 and
32 Å, respectively. Calculating the electron densities points out denser
structures compared with the samples in Set 1. These values are
1.5 e/Å3
for sample E and 1.55 e/Å3
for sample F (see Figure 5B).
Because samples in Set 2 have been prepared with a higher PC, it is
reasonable to imagine that each droplet on the substrate, in the
process of deposition, contains a higher number of solute particles.
This noticeably facilitates the process of joining the individual islands
on the substrate and results in a remarkably compact structure. The
thickness of the deposited thin layers (E: 173 Å, F: 318 Å) remarkably
shows a significant rise compared with the corresponding samples in
Set 1 with the same PV.
We tried to take XRR data for samples G and H. However, the
X-ray fringes were not displayed. This is due to a big root mean square
roughness of their surfaces. The XRR from a layer is proportional to
the Fourier transform of the gradient of EDP normal to the surface.11
An error function can describe a rough interface, then dρ/dz will be
presented by a Gaussian one. The Fourier transform of a Gaussian
function is a Gaussian, too. Consequently, the specular X-ray scatter-
ing falls as qz
−4
e− qzσ
ð Þ2
, legitimating a fast drop in specular XRR for
surfaces of big roughness. Based on this, EDP information cannot be
available for the samples G and H. Despite this conclusion, it is under-
standable that these samples will be quite thicker than E and F.
3.3 | Sheet resistance measurements
The attained values of sheet resistance are plotted in Figure 6. It can
be concluded that thicker samples have less sheet resistance for both
sample sets. This conclusion could be supported by the idea that
thicker samples contain more electrons per unit volume, which will
assist the conduction process. Denser structures will provide more
pathways for charge carriers to go through and then lower the sheet
resistance.
The sheet resistances shown in Figure 6 are identified by two
regions with two different slopes. In the first region, the sheet
resistance decreases from 25.9 MΩ/□□ to 5.84/□□, in the first sam-
ple set, and from 1.14 MΩ/□□ to 0.1 MΩ/□□, in the second sample
set. In the second region, the sheet resistance goes down smoothly.
The significant apportionment of the sheet resistance is due to the
formation process of the SnO2 layer on the glass substrate. There are
evidences14
corroborate that films of a few tens of angstrom thick or
thinner are arranged by small, individual islands separated from each
other by distances of the order of about 100 Å. To establish the elec-
trical conduction in the film, electrons have to be transferred between
the islands across the gaps, and this transfer will determine the con-
ductivity of the film. Based on a simulation done for the spray pyroly-
sis deposition method,15
droplets evaporate before reaching the
substrate and precipitate forms. Then the precipitate will be
TABLE 1 Parameters obtained from XRR data for samples with PC = 0.01 M
Sample PV (mL) Roughness (RMS) (Å) Electron density (e/Å3
) Thickness (Å) Resistivity (Ω-cm)
A 20 6 ± 1 1.20 ± 0.01 50 ± 2.0 12.9 ± 0.2
B 30 15 ± 1 1.25 ± 0.02 99 ± 1.0 5.8 ± 0.2
C 40 22 ± 1 1.30 ± 0.01 107 ± 1.0 4.7 ± 0.3
D 50 24 ± 1 1.35 ± 0.02 215 ± 2.0 8.6 ± 0.1
FIGURE 4 Thickness and electron density of the deposited layers
versus PV
4 ASGHARIZADEH ET AL.
5. converted to a vapor state near the substrate, and adsorbed
molecules on the surface of the substrate will be designed as islands
on the substrate surface.
Starting the deposition, the SnO2 particles were expected to
deposit islands on the glass substrate (first step). Continuing the
deposition with higher PVs, the gap between distant SnO2 islands was
reduced, and finally, the SnO2 islands coalesced. In this step, the
conductivity of the thin layers would be described by the following
equation16
:
σ / exp −2αs−
W
kT
, ð2Þ
where α is the tunneling exponent of electron wave functions in the
insulator, which would be an order of 1010
m−1
for an insulator16
; s is
the separation of islands; W is the island charging energy, which is
inversely proportional to the island size; k and T are the Boltzmann
constant and temperature, respectively. In the above equation, two
elements shape the conductivity: quantum tunneling, which plays a
role in electron transferring between islands, and activation energy to
create a charge carrier associated with placing an electronic charge on
an island. As the interisland separation is inversely proportional to the
island size, one can expect that decreasing the island separation
(increasing the island size) will elevate the tunneling probability in the
ultrathin layers. By utilizing higher PVs, the space between the islands
decreases, and a network structure is established, then the sheet
resistance declines.
The growth progress and surface roughness of the thin layers
govern their electrical properties. By completing the growth steps of a
layer, its conductivity could be described by the quantum size
effect.17
This effect is modeled by Fuchs–Sondheimer (F. S) describing
the behavior of the electrical resistivity as a function of the film
thickness and surface roughness. The limiting form of the F. S model
for very thin layers (k 1) is
ρ
ρ0
=
4
3
1−p
ð Þ
1 + p
ð Þ
1
k log 1
k
, ð3Þ
and for relatively thick films (k 1) is
ρ
ρ0
= 1 +
3
8
1−p
ð Þ
k
, ð4Þ
where ρ/ρ0 is the ratio between the film and bulk resistivity; k = d/λ,
d is the thickness of the film, and λ is the electron mean free path;
p (0 ≤ p ≤ 1) is the specular parameter, defined as the ratio of the
specularly scattered electrons to the total number of reflected ones.
The specular parameter p = 0 stands for a completely diffusive
scattering, while p = 1 describes a completely specular scattering.
For thick films, the specular scattering of the electrons will represent
structures with bulk conductivity. However, diffuse scattering of the
electrons at the interfaces, as a primary mechanism affecting the
resistivity, will reduce the conductivity. At the same time, for very
thin layers, the surface roughness plays an essential role in resistiv-
ity. As for a set of complete specular scattering of the elec-
trons (p = 1), the model predicts a perfect conductive layer with no
resistivity.
The resistivity of the layers can be calculated through the relation
ρ = Rsd, where Rs is the measured sheet resistance. The tabulated
FIGURE 5 A, X-ray specular
reflectivity of the second sample set. The
PC = 0.05 M, and the PV = 20, and 30 mL
for samples E and F, respectively.
B, Electron density profile of the samples
of Set 2 (PC = 0.05 M)
FIGURE 6 The sheet resistance of the thin layers versus PV. The
error bars are less than the legend size
ASGHARIZADEH ET AL. 5
6. resistivity of the samples in Set 1 (Table 1) experiences a decline with
increasing thickness up to about 100 Å after which the resistivity
escalates up. This behavior can be explained by the quantum size
effect through Equation 3. For the samples in set two, the resistivity
of ρ = 1.97 and ρ = 0.32 Ω-cm can be calculated for samples E and F,
respectively. The latter is very close to the bulk resistivity of SnO2
(ρbulk = 0.33 Ω-cm).18
Therefore, considering the Equation 4, one can
expect that the surface roughness of the samples G and H plays no
role in the layer resistivity, and the bulk properties dominate. Based
on this, missing information on layer thicknesses when the XRR
technique is used can be obtained by utilizing the relation between
resistivity and sheet resistance. The values of dG = 785 and
dH = 1,220 Å were estimated.
4 | CONCLUSION
Two sets of the ultra-thin layers prepared by the spray pyrolysis
method were investigated. EDP of the samples deduced from fitting
the XRR data shows that the samples with 0.05 M will produce denser
layers. Varying the PV affects, significantly, the thickness of the layers
and has a negligible effect on the layer density. Meanwhile, altering
the PC mainly changes the layer density. Equally important is that
using higher PCs will lead to layers with less sheet resistance. The
sheet resistance behavior of the thin layers was associated with the
layer growth procedure. In the first step of the growth, the high sheet
resistance of the ultra-thin layers was due to the sizeable interisland
separation. Utilizing higher PVs, the film growth enters into the
second step, where a network structure is formed on the substrate. In
this step, the role of the surface roughness and layer thickness in
conductivity was discussed via quantum size effect and concluded
that the surface roughness for layers of more than almost 200 Å,
prepared by higher PC, has no control over the conductivity. In this
case, the resistivity of the films approaches that of the bulk one. In
contrast, for very thin layers prepared by PC = 0.01 M, the presence
of the surface roughness is crucial in modeling the resistivity.
ORCID
Saeid Asgharizadeh https://orcid.org/0000-0003-0802-4288
Masoud Lazemi https://orcid.org/0000-0003-0118-7113
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How to cite this article: Asgharizadeh S, Lazemi M, Rozati SM,
Sutton M, Bellucci S. Surface roughness and electrical
conductivity of the SnO2 ultra-thin layers investigated by
X-ray reflectivity. Surf Interface Anal. 2020;1–6. https://doi.
org/10.1002/sia.6888
6 ASGHARIZADEH ET AL.