Optimization Of Deposition Parameters Research Articles

Effect of O2Partial Pressure on AlOxThin Films Prepared by Reactive Ion Beam Sputtering Deposition

The barrier and optical properties of AlO x thin films on polycarbonate deposited by Reactive Ion Beam Sputtering (RIBS) were investigated at different oxygen partial pressure. We measured the deposition rate of AlO x thin films. As the oxygen partial pressure increased, the deposition rate increased then decreased. The changes of deposition rate are associated with the properties of deposited films. The properties of deposited AlO x thin films were studied using X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM). Optimum deposition parameters were found for fabricating aluminum oxide thin films with high optical transparency for visible light and low Oxygen Transmission Rate (OTR). The optical transmittance of AlO x thin film deposited on polycarbonate (PC) showed the same value of bare PC.

Optimizing of substrate properties for carbon nanotube production in radiofrequency discharge

We have carried out synthesis of carbon nanotubes by PECVD. The main goal was to find optimum deposition parameters leading to well-controlled growth of the carbon nanotubes (CNTs). The CNTs were grown on silicon substrates with SiO2 layers (100÷200 nm thick) and catalyst layer of Fe or Ni (2÷15 nm thick). We have tried to find the optimal thickness and the way of preparation of the oxide as well as catalyst layer for the uniform synthesis of CNTs. The pre-treatment (creation of catalytic particles) was carried out in r. f. capacitively coupled discharge. We observed to creation of catalytic particles influence on conditions of pre-treatment (thickness of layer, substrate temperature, r. f. power). The properties of catalytic layers were observed by SEM. The best result of pre-treatment we have done for thickness of layer 3 mm and r. f. power 100 W.

Tantalum film for x-ray lithography mask deposited by electron cyclotron resonance plasma source coupled with divided microwaves

An advanced electron cyclotron resonance (ECR) plasma source coupled with divided microwaves has been applied to Ta film formation. The feasibility of the Ta film as an x-ray mask absorber is investigated. The stress in an x-ray absorber material must be low, uniform, and stable. According to the results of an investigation on the stress-depth distribution in Ta film, the stress can be described as the sum of interfacial stress (that retained near the film–substrate interface) and bulk stress (that retained in the film bulk). It is found that these individual stresses can be independently controlled. The interfacial stress depends on the substrate temperature, working-gas pressure, and deposition rate. The bulk stress becomes compressive by adding Ar to the sputtering gas (Xe). A low stress film of 23 MPa (400 nm thick film) with no stress-depth distribution is obtained using optimized deposition parameters of 3.3×10−2 Pa of Xe, 1.75 sccm of Ar, and 280 °C substrate temperature. The ECR Ta film showed excellent stability against stress with a change in stress of less than 5 MPa after the x-ray mask fabrication process and synchrotron radiation irradiation. A highly accurate x-ray mask is fabricated by a wafer process using an ECR-deposited Ta film. The maximum image placement (IP) error of the x-ray mask is less than 60 nm, which includes the IP error induced by membrane shrinkage during back etching.

Hot-filament chemical vapour deposition of nanodiamond on silicon nitride substrates

Nearly continuous nanocrystalline diamond (NCD) films were successfully grown on silicon nitride (Si 3N 4) substrates, after 1 h of deposition time, using hot-filament chemical vapour deposition technique with a gas mixture of Ar–CH 4–H 2. The optimal deposition parameters were: filament temperature≅2200 °C, substrate temperature≅650 °C, Ar/H 2 gas flow ratio=1.2, CH 4/H 2 gas flow ratio=0.04 and gas mass flows of 50 or 100 ml min −1. The identification and characterization of NCD was done by μ-Raman spectroscopy, low incident beam angle diffraction and scanning electron microscopy.

Hot-filament chemical vapour deposition of nanodiamond on silicon nitride substrates

Nearly continuous nanocrystalline diamond (NCD) films were successfully grown on silicon nitride (Si3N4) substrates, after 1 h of deposition time, using hot-filament chemical vapour deposition technique with a gas mixture of Ar–CH4–H2. The optimal deposition parameters were: filament temperature≅2200 °C, substrate temperature≅650 °C, Ar/H2 gas flow ratio=1.2, CH4/H2 gas flow ratio=0.04 and gas mass flows of 50 or 100 ml min−1. The identification and characterization of NCD was done by μ-Raman spectroscopy, low incident beam angle diffraction and scanning electron microscopy.

Pulsed Injection MOCVD of YSZ Thin Films onto Dense and Porous Substrates

AbstractIn this work, we describe the preparation of YSZ layers on dense and porous substrates using the pulsed injection metal–organic (MO) CVD technique. In this technique, the vapor phase is obtained by injecting micro‐droplets of a solution, consisting of the required amounts of Zr(tmhd)4 and Y(tmhd)3 precursors in monoglyme, into a heated evaporator. The droplet characteristics (volume, precursor concentration, and injection frequency) were studied in order to control the growth rate and the microstructure of the layers. The optimum deposition parameters needed to achieve dense film microstructure on dense substrates were determined. For these optimized experimental conditions, we evaluated the growth rate of the layers as a function of temperature. The activation energy in the kinetically limited regime was found to be 96 kJ mol–1. The structure of the layers was analyzed as a function of the film composition. A concentration of 11 mol‐% of yttria fully stabilizes the cubic phase. This process has been applied to the preparation of dense YSZ membranes on porous substrates in order to use the YSZ layer as a solid electrolyte (SE) in electrochemical devices such as solid oxide fuel cells (SOFC), oxygen sensors, and generators. Dense YSZ layers were obtained on samples of porous alumina, and on YSZ‐Ni cermets. Characterization by scanning electron microscopy (SEM) and X‐ray diffraction (XRD) showed no cracks or voids along the grain boundaries, nor secondary phases due to chemical interaction with the substrate.

Development of highly conducting p-type μc-Si:H films from minor diborane doping in highly hydrogenated SiH 4 plasma

Boron-doped microcrystalline Si:H (μc-Si:H) films have been prepared from (SiH 4+H 2+B 2H 6)-plasma in rf glow discharge. Very low level of B 2H 6 dilution is required to maintain a microcrystalline network. Dopant-induced defects at higher B 2H 6 dilution perturb the crystallization process. However, higher hydrogen dilution to the plasma enhances the doping efficiency at the silicon network while maintaining the microcrystallinity. Optimization of deposition parameters resulted in p-type μc-Si:H films of σ D∼4.2 S cm -1 with an average grain size of 270 Å and exhibiting (111), (220) and (311) sharp crystallographic planes of c-Si in the electron diffraction pattern.

Electrophoretic Prepared ZnGa2 O 4 Phosphor Film for FED

In this study, the low voltage phosphor film for field emission display (FED) is prepared by electrophoresis. The influence of the deposition parameters, such as deposition time, deposition voltage, electrode distance, and stirring speed on the electrophoresis and luminescence of phosphor film are investigated. The optimal deposition parameters for electrode distance, stirring speed, electrode bias, and deposition time are 20 mm, 450 rpm, 50 V, and 40 s, respectively. The optimum phosphor film thickness is 8-10 μm. For improving the crystallization and luminescence of the as-deposited phosphor film, it is annealed in various atmospheres. A luminance of 2080 cd/m2 is obtained when phosphor film is annealed in atmosphere and measured at an electron-gun voltage of 5 kV and an anode current of 30 A. The luminance efficiency of phosphor films prepared by electrophoresis is about 15 times higher than that prepared by the sedimentation method. © 2003 The Electrochemical Society. All rights reserved.

Improvement of IBAD MgO template layers on metallic substrates for YBCO HTS deposition

We present our results to improve ion beam assisted deposition (IBAD) of magnesia (MgO) templates for subsequent YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) deposition. The substrate surface roughness has a significant effect on the initial nucleation texture of IBAD MgO films. We have found that reduction in our substrate surface roughness to /spl sim/ 3.5 nm has resulted in better in-plane texture for IBAD MgO films than those deposited on rougher metal substrates. We have further improved the IBAD MgO deposition parameters by using an in situ reflected high-energy electron diffraction (RHEED) analysis tool that allows for monitoring of IBAD MgO growth. We have found a direct correlation between the RHEED generated intensity versus time curve and in-plane texture. Utilizing X-ray diffraction analysis, we have been able to determine the optimum deposition parameters to routinely grow films in batch mode that have a phi scan /spl Delta//spl phi/ from 6 - 7/spl deg/. Coupling the improvements in substrate preparation with optimization of IBAD MgO deposition has allowed for both batch and continuous deposition (termed c-IBAD MgO) on metallic substrates that result in superior superconducting properties. We have demonstrated that deposited meter lengths have had phi scan FWHM values from 8 - 9/spl deg/ with /spl plusmn/ 10% uniformity. Additionally, we have been able to widen the processing zone in our system and coat two, one-meter lengths simultaneously while preserving good texture quality (/spl Delta//spl phi//sub ave/ /spl sim/ 8/spl deg/) and uniformity (60 - 80% of tape length within /spl plusmn/ 5% of /spl Delta//spl phi//sub ave/) for both tapes.

Microstructural and macroscopic properties of cold sprayed copper coatings

Cold spraying is a coating technique in which the formation of dense, tightly bonded coatings occurs only due to the kinetic energy of high velocity particles of the spray powder. These particles are still in the solid state as they impinge on the substrate. This study correlates optimized deposition parameters with the corresponding microstructure as well as mechanical and conductive behavior of cold sprayed copper coatings in order to explain possible bonding mechanisms. In addition, the performance of cold sprayed copper coatings is compared to that of cold rolled copper and to coatings prepared by thermal spray methods.

CuInS2/PEDOT Photovoltaic Structure

AbstractStructures based on combination of electrically conductive polymers with inorganic semiconductors are currently intensively investigated with the aim to prepare low-cost, largearea and flexible photovoltaic devices. In this study, multilayer structures consisting of CuInS2 (CIS) and poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrenesulfonate (PSS) thin films were prepared and investigated for photovoltaic applications. Polycrystalline CIS absorber layers were synthesized on top of a layered structure on Cu tape substrate using socalled non-vacuum CISCuT technique. Thin PEDOT buffer layers doped with PSS were deposited onto KCN etched and vacuum annealed CIS films. The deposition was performed using the spin-casting technique from an aqueous dispersion of PEDOT/PSS mixed with Nmethylpyrrolidone, isopropanol, glycerin and epoxysilane additives. Optimal deposition parameters for stable PEDOT films with a good adherence to the surface of CIS were selected experimentally. The morphology and thickness of prepared films and structures was determined using SEM technique. Average film thickness was about of 1.5 μm for CIS and 50 nm for PEDOT films. Current-voltage and impedance characteristics were measured. Significant photovoltage and photocurrent of the photovoltaic structures were observed under standard illumination intensity. The best structure showed an open-circuit voltage of 510 mV and a shortcircuit current density of 20.2 mA/cm2.

Characterisation of GaN films grown on sapphire by low-temperature cyclic pulsed laser deposition/nitrogen rf plasma

GaN thin films grown by cyclic pulsed laser deposition were characterised by X-ray diffraction (XRD), photoluminescence (PL), and atomic force microscopy. Films were grown on pre-nitridated c-plane sapphire at two substrate temperatures (600 and 650 °C). Films deposited at 650 °C exhibit a higher growth rate which is reflected in the XRD intensity along the GaN (0 0 0 2) direction. At this substrate temperature, the quality of the PL spectrum was the best. The typical yellow luminescence, YL (2.2 eV) was dominant at the lower deposition temperature. For this substrate temperature change, the near band edge emission (NBE) to YL ratio increased from 0.3 to a value of 17. This NBE emission was peaked at 3.47 eV with a FWHM of 200 meV at 14 K. Optimisation of deposition parameters is suggested to further improve the quality of binary films.

Er:Y 2O 3 thin films grown by pulsed laser deposition

Deposition of thin films by pulsed laser ablation from an Er 2O 3:Y 2O 3 ceramic target for waveguide laser application is reported. Erbium-doped yttrium oxide (Er:Y 2O 3) thin films are grown on c-cut sapphire under optimized deposition parameters. The effects of ultraviolet (UV)-assisted annealing of thin Er:Y 2O 3 films on the structural properties and the morphology are investigated. The films exhibit better crystalline structure and smoother surface after post-deposition treatment. The optical transmission spectra and the waveguiding properties of the thin films are reported. The films exhibit lower absorption and scattering losses after UV-assisted annealing. The light is guided to the end of the treated films with propagation losses ≈2 dB/cm.

The microstructure and X-ray reflectivity of Mo/Si multilayers

We have studied microstructure Mo/Si multilayers grown by RF and DC sputtering at different deposition parameters by cross-sectional transmission electron microscopy and X-ray reflectivity for the wavelength 13.4 nm and 0.154 nm. It is shown experimentally that reflection properties of mirrors are determined by the crystalline state of molybdenum layers. The results are compared for the different samples and discussed in view of the choice an optimal deposition parameters to produce multilayers with a high X-ray reflectivity for the λ=13.4 nm.

Peltier effect in a co-evaporated Sb 2Te 3(P)-Bi 2Te 3(N) thin film thermocouple

A thin film Sb 2Te 3-Bi 2Te 3 based thermocouple was fabricated by co-evaporation. The conditions for deposition have been investigated as a function of substrate temperature ( T s) and flux ratio [ F r= F(Te)/ F(Sb,Bi)] and optimised to achieve a high thermoelectric power factor. It has been observed that the Seebeck coefficient and electrical conductivity of p-type Sb 2Te 3 thin films (α p, ρ p) and n-type Bi 2Te 3 thin films (α n, ρ n) deposited by co-evaporation were found to be approximately 160 μV/K, 3.12×10 −3 Ωcm and −200 μV/K, 1.29×10 −3 Ωcm, respectively. From optimal deposition parameters, a thin film thermocouple was fabricated and operated in Peltier mode. The observed maximum value for temperature difference between hot and cold end is approximately 15.5 K for a current of 55 mA. The figure of merit and coefficient of performance of the thermocouple are estimated.

Comprehensive study of microcrystalline silicon solar cells deposited at high rate using 13.56 MHz plasma-enhanced chemical vapor deposition

In this article we present a comprehensive study of microcrystalline silicon (μc-Si:H) p-i-n solar cells prepared by using plasma-enhanced chemical vapor deposition (PECVD) at 13.56 MHz excitation frequency. In the first step the cell development was performed in a small area PECVD reactor showing the relationship between the deposition process parameters and the resulting solar cell performance. Subsequent up-scaling to a substrate area of 30×30 cm2 confirmed the scalability of optimized deposition parameters to large area reactors. We investigated the deposition regime of high rf power Prf (0.25–0.7 W/cm2) and high deposition pressure pdep (1–11 Torr) for the μc-Si:H i layer. Furthermore, the influence of silane concentration and deposition temperature was studied. A transition between amorphous and microcrystalline growth could be achieved by a variation of either deposition pressure, plasma power, or silane concentration. The best microcrystalline silicon solar cells were prepared close to the transition to amorphous growth. A high deposition pressure was a prerequisite for obtaining high quality material at a high growth rate. The best solar cell efficiencies achieved so far are 8.1% and 6.6% at i-layer growth rates of 5 and 10 Å/s, respectively, for μc-Si:H single junction cells. Applied in a-Si:H/μc-Si:H tandem cells a stabilized efficiency of 10.0% was achieved.

Ordered films of a new substituted diphenyl-1,3,4-oxadiazole for application in light emitting devices

The formation of highly ordered layers of oxadiazoles by vapor deposition (VD) aims to built structures characterized by the emission of polarized light. In this paper the formation of multilayer structures depending on preparation parameters is described. Essential deposition parameters are the substrate temperature and the deposition rate. Systematic variation of these parameters and structure investigation of the resulting samples by means of X-ray specular reflection (XSR) and scanning force microscopy (SFM) were used to get insight into the film growth mechanism. A comparison of the length of the molecules extended chain conformation with the layer periodicity derived from X-ray data ( d=4.9 nm) reveals a bilayer structure. SFM images of samples formed at optimum deposition parameters show a smooth topography with bilayer steps. This indicates a bilayer-by-bilayer growth mechanism. The vapor deposited oxadiazole films show fluorescence with a maximum intensity at a wavelength of 382 nm.

Optimization of process parameters in a large-area hot-wire CVD reactor for the deposition of amorphous silicon (a-Si:H) for solar cell application with highly uniform material quality

Abstract Scale-up of a-Si:H-based thin film applications such as solar cells, entirely or partly prepared by hot-wire chemical vapor deposition (HWCVD), requires research on the deposition process in a large-area HWCVD system. The influence of gas supply and filament geometry on thickness uniformity has already been reported, but their influence on material quality is systematically studied for the first time. The optimization of deposition parameters for obtaining best material quality in our large-area HWCVD system resulted in an optimum filament temperature, T fil ≈1600°C, pressure, p =8 mTorr and silane flow, F(SiH 4 )=100 sccm, keeping the substrate temperature at T S =200°C. A special gas supply (gas shower with tiny holes of uniform size) and a filament grid, consisting of six filaments with an interfilament distance, d fil =4 cm were used. The optimum filament-to-substrate distance was found to be d fil–S =8.4 cm. While studying the influence of different d fil and gas supply configurations on the material quality, the above-mentioned setup and parameters yield best results for both uniformity and material quality. With the setup mentioned, we could achieve device quality a-Si:H films with a thickness uniformity of ±2.5% on a circular area of 20 cm in diameter. The material, grown at a deposition rate of r d ≈4 A/s, was characterized on nine positions of the 30 cm×30 cm substrate area, and revealed reasonable uniformity of the opto-electronic properties, e.g photosensitivity, σ Ph / σ D =(2.46±0.7)×10 5 , microstructure factor, R =0.17±0.05, defect densities, N d(PDS) =(2.06±0.6)×10 17 cm −3 and N d(CPM) =(2.05±0.5)×10 16 cm −3 (film properties are given as mean values and standard deviations). Finally, we fabricated pin solar cells, with the i-layer deposited on small-area p-substrates distributed over an area of 20 cm×20 cm in this large-area deposition system, and achieved high uniformity of the cell parameters with initial efficiencies of η =(6.1±0.2)% on the 20 cm×20 cm area.

Li 3Sc 2− xFe x(PO 4) 3 thin films and powders prepared by ultrasonic spray pyrolysis

Thin films of Li 3Sc 2− x Fe x (PO 4) 3 ( x=0.5, 2) solid electrolytes have been prepared on quartz glass substrates by ultrasonic spray pyrolysis (USP) using aqueous solutions of LiH 2PO 4, Sc(NO 3) 3 and Fe(NO 3) 3 at substrate temperature of 500–700°C. The amorphous as-deposited films were converted into crystalline materials by heat treatment at 800–1000°C. The optimal deposition parameters for formation of uniform precursor films with good adhesion to the substrate were determined. The dense films composed of fine columnar grains were obtained using the three cycles of deposition and annealing. The room temperature ionic conductivity of the film with the composition x=0.5 was 5×10 −6 S/cm. The superionic γ-phase of USP ceramics of Li 3Sc 2− x Fe x (PO 4) 3 (0< x≤0.6) was shown to be stabilized at room temperature, which may be caused by slight structural distortions and changes in the interactions between the lithium ions during Sc 3+→Fe 3+ substitution. The highest ionic conductivity σ(25°C)≈1×10 −5 S/cm was observed for ceramics with x=0.4.

Saturated defect densities of hydrogenated amorphous silicon grown by hot-wire chemical vapor deposition at rates up to 150 Å/s

Hydrogenated amorphous-silicon (a-Si:H) is grown by hot-wire chemical vapor deposition (HWCVD) at deposition rates (Rd) exceeding 140 Å/s (∼0.8 μm/min). These high rates are achieved by using multiple filaments and deposition conditions different than those used to produce our standard 20 Å/s material. With proper deposition parameter optimization, an AM1.5 photo-to-dark-conductivity ratio of 105 is maintained at an Rd up to 130 Å/s, beyond which it decreases. In addition, the first saturated defect densities of high Rd a-Si:H films are presented. These saturated defected densities are similar to those of the best HWCVD films deposited at 5–8 Å/s, and are invariant with Rd up to 130 Å/s.