Function Of Deposition Time Research Articles

Ellipsometry study of process deposition of amorphous Indium Gallium Zinc Oxide sputtered thin films

This paper reports on an InGaZnO optical study by spectrometric ellipsometry. First of all, the fitting results of different models and different structures are analysed to choose the most appropriate model. The Tauc–Lorentz model is suitable for thickness measurements but a more complex model allows the refractive index and extinction coefficient to be extracted more accurately. Secondly, different InGaZnO process depositions are carried out in order to investigate stability, influence of deposition time and uniformity. Films present satisfactory optical stability over time. InGaZnO optical property evolution as a function of deposition time is related to an increase in temperature. To understand the behaviour of uniformity, mapping measurements are correlated to thin film resistivity. Results show that temperature and resputtering are the two phenomena that affect IGZO uniformity.

Investigation of quantum confinement within the tunneling-percolation transition for ultrathin bismuth films

We investigate conduction phenomena in ultrathin bismuth (Bi) films that are thermally evaporated onto flat quartz. Critical points in the conductance as a function of deposition time are identified and used to scale the data from time dependence to coverage dependence. The resulting nonlinear coverage scaling equation is verified independently via analysis done on transmission electron microscope images of the evaporated films. The scaled data yields critical exponents in very good agreement with classical percolation theory, and clearly shows the transition from the tunneling regime into percolation. Surprisingly, no noticeable signatures of size-quantization effects in the nucleation sites as a function of deposition time is observed in either regime. We discuss our findings in light of Boltzmann transport modeling of 1D conduction as an approximation to the narrow percolative paths that form at the onset of percolation. Our results suggest that lack of a preferred crystallite orientation in the nucleation process may indeed cause quantum-confinement to be too smeared out to be observable in the tunneling to percolation transition.

Surface Cleaning of SiGe(100) and Passivation of Ge(100) with Aqeuous Ammonium Sulfide

As scaling of microelectronic devices continues, germanium and silicon-germanium are promising materials for integration into silicon-based technology. Germanium and silicon-germanium based field-effect transistors can reduce leakage current and consume less power by means of improved carrier mobility and a narrower band gap, as opposed to traditional electronics. However, silicon-germanium surfaces are more challenging to work with because the topmost surface layer is comprised of germanium oxides that complicate cleaning and passivation processes. Here we seek to obtain a smooth, oxide free SiGe surface and hope to garner an understanding of the best conditions to effectively remove surface oxides. Additionally, we hope to further our understanding of aqueous ammonium sulfide passivation processes on Ge surfaces that will prevent re-oxidation of the surface for applications towards modern field-effect transistors (FETs). The first portion of this work focuses on the removal of oxides from the SiGe surface with 50 and 75% Ge molar ratios using a variety of aqueous processes. These processes include SC-1, HCl, HF, and HCl/HF mixtures. The SiGe surface was characterized using X-ray photoelectron Spectroscopy (XPS) after each chemical treatment. Film thicknesses were measured using spectroscopic ellipsometry. Immersion in HCl showed similar results to as shipped samples and was ineffective in removing surface oxides. Aqueous HF, however, removed both surface oxides and carbon contamination. SC-1 treatments selectively reduced the Ge in the SiGe film and left the surface enriched in Si, which oxidized as confirmed by XPS. If the Ge could be completely removed from the top-most layer, the SiO2 layer that forms could be used to passivate the SiGe surface and avoid problematic Ge oxides. Ellipsometry results showed that SC-1 solutions (NH4OH:H2O2:H2O, 1:1:100 v/v) etched 1 nm of the SiGe film, which was then oxidized. Ge 2p to Si 2p XPS peak ratios confirmed that increasing concentrations of SC-1 depleted the Ge content on the surface from 0.8 to 0.4, confirming the enrichment of the surface in Si. Ge to Si peak area ratios as a function of the SC-1 dilution factor showed a non-linear trend for SiGe 50% surfaces. Passivation of Ge with aqueous (NH4)2S was also studied. Because Ge oxides are unstable and water soluble, it is advantageous to remove them and deposit a sulfur layer to prevent further oxidation when exposed to air. Surface passivation was studied as a function of deposition time, solution concentration and the addition of H2O2. Passivation of the surface was ineffective at times below 20 min. Changing the concentration of (NH4)2S also had no noticeable effect on the surface based on XPS. Furthermore, at high ammonium sulfide concentrations the addition of H2O2 did not affect the passivation process. The addition of H2O2 to dilute (NH4)2S showed poor passivation due to oxidation of the surface by H2O2.

Antimicrobial Air Filters Using Natural Euscaphis japonica Nanoparticles.

Controlling bioaerosols has become more important with increasing participation in indoor activities. Treatments using natural-product nanomaterials are a promising technique because of their relatively low toxicity compared to inorganic nanomaterials such as silver nanoparticles or carbon nanotubes. In this study, antimicrobial filters were fabricated from natural Euscaphis japonica nanoparticles, which were produced by nebulizing E. japonica extract. The coated filters were assessed in terms of pressure drop, antimicrobial activity, filtration efficiency, major chemical components, and cytotoxicity. Pressure drop and antimicrobial activity increased as a function of nanoparticle deposition time (590, 855, and 1150 µg/cm2filter at 3-, 6-, and 9-min depositions, respectively). In filter tests, the antimicrobial efficacy was greater against Staphylococcus epidermidis than Micrococcus luteus; ~61, ~73, and ~82% of M. luteus cells were inactivated on filters that had been coated for 3, 6, and 9 min, respectively, while the corresponding values were ~78, ~88, and ~94% with S. epidermidis. Although statistically significant differences in filtration performance were not observed between samples as a function of deposition time, the average filtration efficacy was slightly higher for S. epidermidis aerosols (~97%) than for M. luteus aerosols (~95%). High-performance liquid chromatography (HPLC) and electrospray ionization-tandem mass spectrometry (ESI/MS) analyses confirmed that the major chemical compounds in the E. japonica extract were 1(ß)-O-galloyl pedunculagin, quercetin-3-O-glucuronide, and kaempferol-3-O-glucoside. In vitro cytotoxicity and disk diffusion tests showed that E. japonica nanoparticles were less toxic and exhibited stronger antimicrobial activity toward some bacterial strains than a reference soluble nickel compound, which is classified as a human carcinogen. This study provides valuable information for the development of a bioaerosol control system that is environmental friendly and suitable for use in indoor environments.

Time dependent synthesis of crystalline Bi2S3 and its application as a sensitizer in SnO2 based solar cells

Abstract In the present study, thin films of Bi2S3 with hollow morphology were deposited by chemical bath deposition at room temperature. The structural, morphological and optical properties of Bi2S3 films were investigated as a function of deposition time. To study the photovoltaic properties, sensitization of SnO2 photoanode with Bi2S3 was achieved successfully via chemical bath deposition. The solar cell fabricated using SnO2–Bi2S3 photoanode showed an open circuit voltage (V OC) of 357 mV, short circuit current density of (J SC) 740.16 μA cm−2 and fill factor (F.F.) of 31%.

Evaluation of the Growth Mechanism of Ti-Containing Conversion Coatings Using XPS

Ti-containing coatings as chromate replacement were prepared on electrogalvanized steel. Zinc coatings were deposited from a weak acid chloride bath. Cr-free conversion coatings were deposited from bath composed of: TiCl3, H2SiF6, H2O2 and oxalic acid. XPS was used to evaluate chemical composition of the coatings as a function of deposition time. Deposited coating were of conversion type. Regardless of the achieved conversion coating thickness, Zn from the substrate was always present. In the coatings were identified: Zn2SiO4 / Zn4Si2O7(OH)2, ZnTiO3, ZnO, Zn (OH)2, Zn0, SiOx and Ti-O-Si in varying proportions. The chemical composition of the outer surface of the coating depended on deposition time, e.g. in a time interval 0-300 s 30 fold increase of the Si:Ti ratio and 20 fold of the Si:Zn ratio were observed. Estimated thickness of conversion coating was 3, 14, 35, and 100 nm for the time deposition of 1, 40, 80 and 300 s respectively. It is the proposed model for distinguishing Zn (0) phase from Zn (2+) quantitatively, based on the Zn L3M45M45 spectrum. The composition of the ZnTiSi conversion coating determined its mechanical properties and corrosion resistance. Standard tests carried out showed that the coatings obtained at the time of 20-40 s had the best corrosion performance and mechanical resistance

Synthesis of polymer nanoparticles via vapor phase deposition onto liquid substrates.

In this article, the growth of polymer nanoparticles formed at the liquid-vapor interface via vapor phase polymerization is studied. The particles grow by polymer aggregation, which is driven by the surface tension interaction between the liquid and polymer. It is demonstrated that the mechanism of particle growth is determined by whether polymer particles remain at the liquid-vapor interface or submerge into the liquid. The position of the particles depends on the interaction between the polymer and the liquid. For example, the deposition of poly(n-butyl acrylate) onto poly(dimethyl siloxane) and Krytox liquids leads to the formation of nanoparticles that remain at the liquid-vapor interface. The size of these particles increases as a function of deposition time. The deposition of poly(4-vinylpyridine) onto poly(dimethyl siloxane) and Krytox leads to the formation of nanoparticles that submerge into the liquid. The size of these particles does not significantly change with deposition time. Our study offers a new rapid, one-step synthetic approach for fabricating functional polymer nanoparticles for applications in catalysis, photonics, and drug delivery.

Evolution of Magnetic and Structural Properties during Iron Plating of Carbon Nanotubes

Iron nanoparticles have been electrochemically deposited onto carbon nanotube (CNT) films. The CNT films were prepared by electrophoretic deposition using CNTs that were functionalized using a novel ozone-based process. Chemical characterization of the iron films was undertaken as a function of deposition time and related to their magnetic properties. In the initial stage of film growth, 20 nm cubic iron-rich crystals nucleate on individual CNTs. As the film grows, the iron crystals coalesce into a more continuous film and the elemental iron concentrations increase above 70 atomic percent. Changes in the chemical composition of the films during growth are reflected in the ferromagnetic properties, which show much higher coercivity values for thicker films relative to bulk iron. The film coercivity is related to the nanosized-cubic iron particles which form on the CNTs and is significantly enhanced when compared to that of iron films that form on planar graphite substrates, where the cubic crystal structur...

Role of Thiourea in the Kinetic of Growth of the Chemical Bath Deposited ZnS Films

ZnS films were deposited onto glass substrates by the chemical bath technique at temperatures from 60 to 90°C. Zinc chloride, potassium hydroxide, ammonium nitrate, and thiourea were used as chemical components. According to the species distribution diagrams, the concentration of the chemical components were maintained constant except for thiourea whose concentration is required to decrease when the bath temperature increases, in order to maintain constant the Zn(OH)2 −4/HS− ions concentration. To investigate the kinetic of growth of the ZnS films, their thicknesses were measured as a function of deposition time and bath temperature. The activation energy value estimated for the growing process was Ea = 44.9 kJ/mol which is typical for chemical reactions. The mean value of the bandgap energy of the films was 3.67 eV with optical transmittances up to 80% for all bath temperatures. The rms-roughness of the deposited films was observed to decrease when the bath temperature increases. Results of X-ray diffraction analysis on deposited films reveal a cubic (111) as preferential orientation. Additionally, SEM-EDS results of the ZnS films shows a stoichiometry ratio of [Zn/S] = 0.4–0.6 for all deposition times and bath temperatures.

Characterization of Plasma Polymerized Hexamethyldisiloxane Films Prepared by Arc Discharge

Herein, we present a simple method for fabricating plasma polymerized hexamethyldisiloxane films (pp-HMDSO) possessing superhydrophobic characteristics via arc discharge. The pp-HMDSO films were deposited on a soda–lime–silica float glass using HMDSO monomer vapor as a precursor. A detailed surface characterization was performed using scanning electron microscopy and atomic force microscopy. The growth process of the pp-HMDSO films was investigated as a function of deposition time from 30 to 300 s. The non-wetting characteristics of the pp-HMDSO films were evaluated by means of contact angle (CA) measurements and correlated with the morphological characteristics, as obtained from microscopy measurements. The deposited films were found to be nano-structured and exhibited dual-scale roughness with the static CA values close to 170°. Fourier transform infrared spectroscopy analysis was carried out to investigate chemical and functional properties of these films. Methyl groups were identified spectroscopically to be present within the pp-HMDSO films and were proposed to result in the low surface energy of material. The synergy between the dual-scale roughness and low surface energy resulted in the superhydrophobic characteristics of the pp-HMDSO films. A possible mechanism for the pp-HMDSO film formation is proposed.

Quantitative evaluation of electrophoretic deposition kinetics of graphene oxide

The electrophoretic deposition (EPD) technique is an attractive approach for development of graphene and graphene oxide (GO) films for a variety of applications. However, in order to establish the influence of the EPD parameters on the properties of the deposited films, a deeper investigation of the fundamental GO-EPD kinetics is required. Previous studies have reported a simultaneous anodic reduction of GO flakes during EPD, complicating the kinetics and process control. Therefore, in this study, low voltages were used to prevent significant GO reduction during EPD, as confirmed by XPS and FTIR. Accordingly, the GO-EPD kinetics was established as a function of deposition time and voltage, accompanied by microscopic characterization of the deposited films. The experimental results show that the deposition follows a linear growth law, in good agreement with the predictions of Hamaker’s law. Comparisons of optical absorbance and profilometry provide estimates of (reduced) GO deposition rate, extinction coefficient, and density.

Investigation of metal sulfide optical thin film growth in low-loss IR hollow glass waveguides

In this study, the film growth kinetics for near and mid-IR reflection enhancing CdS and PbS dielectric thin films in HGWs is experimentally established. Crucial fabrication parameters including solution concentrations, pH, and fluid velocity are optimized. The film thickness of these films in HGWs is studied as a function of deposition time and temperature. Through IR spectral response analysis, the dielectric thin film thicknesses were determined and found to have a strong linear time dependence. Accurate metal sulfide film growth models in HGWs were developed, allowing for direct determination of necessary deposition times to yield metal sulfide HGW thin film coatings having a desired response.

Synthesis and characterization of zirconium oxynitride ZrOxNy coatings deposited via unbalanced DC magnetron sputtering

A study of structure, morphology, and corrosion resistance was performed on zirconium oxynitride thin films deposited on 304 and 316 stainless steels by the DC sputtering magnetron unbalance technique. Structural analysis was carried out using X-ray diffraction (XRD), while morphological analysis was performed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). These studies were performed as a function of deposition time via DC sputtering at room temperature (287 K) with an Ar/air flow ratio of 3.0 and a total deposition time of 30 min. The oxynitride films were grown with cubic crystalline structures Zr2ON2 and preferentially oriented along the (222) plane. Chemical analysis determined that in the last 5.0 nm, the Zr coatings present the following spectral lines: Zr3d3/2 (184.6 eV) and 3d5/2 (181.7 eV), O1s (531.3 eV), and N1s (398.5 eV).The zirconium oxynitride films enhance the stainless steel's resistance to corrosion. The protective efficacy has been evaluated using electrochemical techniques based on linear polarizations (LP). The results indicate that the layer provides good resistance to corrosion in chloride-containing media. SEM analysis presented the homogeneity of the films. AFM studies indicated that the average roughness of the film is 20.2 nm in the two steels and a particle size ranging between 150 and 208 nm in ZrOxNy-AISI 316 and 115–180 in ZrOxNy-AISI 316. TEM analysis indicated columnar growth.

Interface engineering for the TaN/Ta barrier film deposition process to control Ta-crystal growth

As a consequence of device shrinking the resistivity of the widely used TaN/Ta double barrier layer becomes an increasingly important parameter for device speed beyond the 32nm technology node. In this study we describe the optimization of the deposition of TaN/Ta stacks in such a way that tantalum nitride layer thickness is minimized and tantalum grows in the favorable conducting @a-phase. In the first part of the study we used in situ ARXPS to investigate the growth of different tantalum nitride layers on SiO2 and SiOCH as a function of deposition time, nitrogen flow and deposition power. In the second part we analyzed the crystalline phase of a 20nm thick tantalum layer deposited on top of the same series of tantalum nitride layers characterized in the growth study. The main findings are the appearance of tantalum carbide and tantalum silicide as interface species for the deposition on SiOCH and only tantalum silicide for the deposition on SiO2. We found that @a-tantalum grows preferably on tantalum carbide and nitrogen rich intermediate layers whereas silicide at the interface promotes the growth of @b-tantalum. To verify these findings we studied two additional modifications of the interface. A lower bias power for a deposition of tantalum nitride on SiO2 was used to confirm the role of tantalum silicide and a thermal treatment of a thin tantalum layer on SiOCH was applied to confirm the role of tantalum carbide. Finally, the contact resistance in via chains on patterned wafers for four selected processes showed the same trends as the sheet resistance of the corresponding barrier films on blanket wafer experiments.

The β to α phase transition of tantalum coatings deposited by modulated pulsed power magnetron sputtering

Tantalum coatings are of particular interest today as promising candidates to replace potentially hazardous electrodeposited chromium coatings for tribological and corrosion resistant applications, such as the internal lining on large-caliber gun barrels. Tantalum coatings have two crystalline phases, α-Ta (body-centered-cubic) and β-Ta (metastable tetragonal) that exhibit relatively different properties. Alpha-Ta is typically preferred for wear and corrosion resistant applications and unfortunately, is very difficult to deposit without the assistance of substrate heating or post-annealing treatments. Furthermore, there is no general consensus on the mechanism which causes α or β to form or if there is a phase transition or transformation from β→α during coating deposition. In this study, modulated pulsed power (MPP) magnetron sputtering was used to deposit tantalum coatings with thicknesses between 2 and 20μm without external substrate heating. The MPP Ta coatings showed good adhesion and low residual stress. This study shows there is an abrupt β→α phase transition when the coating is 5–7μm thick and not a total phase transformation. Thermocouple measurements reveal substrate temperature increases as a function of deposition time until reaching a saturation temperature of ~388°C. The importance of substrate temperature evolution on the β→α phase transition is also explained.

Epitaxial-like Growth of Co3O4/ZnO Quasi-1D Nanocomposites

The development of quasi-1D Co3O4/ZnO nanocomposites by a two-step plasma enhanced-chemical vapor deposition (PE-CVD) process is presented. Arrays of ⟨001⟩ oriented ZnO nanorods were first grown on Si(100) and subsequently used as templates for the PE-CVD of Co3O4, whose amount was tailored as a function of deposition time. The obtained composites were thoroughly characterized by means of a multitechnique approach, involving field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDXS), micro-Raman and Fourier-transform infrared (FT-IR) spectroscopies, X-ray photoelectron and X-ray excited Auger electron spectroscopies (XPS, XE-AES), glancing incidence X-ray diffraction (GIXRD), and reflection high energy electron diffraction (RHEED). The use of moderate deposition temperatures (≤300 °C), together with the unique activation provided by nonequilibrium plasmas, prevented undesired solid-state reactions between the two oxides and promoted Co3O4 growth on the tips of vertic...

Structural and optical studies of chemically deposited Sn2S3 thin films

Sn2S3 thin films were grown on commercial glass substrates by chemical bath deposition at room temperature. The structural and optical properties of Sn2S3 thin films were studied as a function of deposition time. The thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and UV–vis spectroscopy. The XRD pattern showed that the Sn2S3 thin films had an orthorhombic polycrystalline structure. The lattice constants of the thin films were a=8.741Å, b=14.034Å and c=3.728Å. The characteristic bonds of Sn2S3 were observed at 66.3, 111.7, 224.7 and 308.9cm−1 using Raman shift experiment. The optical energy band gap of the thin films decreased from 2.12eV to 2.03eV with increasing deposition time from 20 to 24h. The optical constants of the thin films were obtained using the experimentally recorded transmission data as a function of the wavelength.

Effect of particle size on iron nanoparticle oxidation state

Selecting catalyst particles is a very important part of carbon nanotube growth, although the properties of these nanoscale particles are unclear. In this article iron nanoparticles are analyzed through the use of atomic force microscopy and x-ray photoelectron spectroscopy in order to understand how the size affects the chemical composition of nanoparticles and thus their physical structure. Initially, atomic force microscopy was used to confirm the presence of iron particles, and to determine the average size of the particles. Next an analytical model was developed to estimate particle size as a function of deposition time using inputs from atomic force microscopy measurement. X-ray photoelectron spectroscopy analysis was then performed with a focus on the spectra relating to the 2p Fe electrons to study the chemical state of the particles as a function of time. It was shown that as the size of nanoparticles decreased, the oxidation state of the particles changed due to a high proportion of atoms on the surface.

Antimicrobial Cu-functionalized surfaces prepared by bipolar asymmetric DC-pulsed magnetron sputtering (DCP)

Cu-cotton fabrics were functionalized by bipolar asymmetric DC-pulse magnetron sputtering (DCP). The DCP of Cu-particles on cotton proceeds at a higher energy than DC-magnetron sputtering (DC). The different sputtering mode showed effects on the structure of the Cu-film on the textile. The Cu-layer thickness was observed to be a function of DCP time being the rate of atomic deposition of 2.5 × 10 15 atoms/cm 2 s at 300 mA. The fastest Escherichia coli inactivation was observed within 10 min when Cu was sputtered on cotton Cu for 60 s. This led to a film thickness of 30 nm (150 Cu-layers) with 1.7 × 10 17 atoms/cm 2. The Cu-textiles became darker at longer sputtering times as detected by diffuse reflectance spectroscopy (DRS). By transmission electron spectroscopy (TEM), Cu-particles 35–50 nm in size were found and became more compact on the cotton surface as a function of deposition time. X-ray photoelectron spectroscopy (XPS) was used to determine the surface atomic concentration of O, Cu C, and N along the states of oxidation of the Cu-ions during the redox process leading to E. coli inactivation. The oxidation of the E. coli on the Cu-cotton surface was a function of reaction time and was monitored by the oxidation index of the carbon species on the fabric according to the ratio: (C–OH)/(C–C, C C, C–H). The increase in hydrophobicity of the Cu-cotton was followed as a function of the contact angle and droplet residence time for different samples. The results obtained for the E. coli inactivation on the Cu-films are discussed suggesting a possible reaction mechanism.

Preparation of SnTe thin films on Au(1 1 1) by electrodeposition route

Tin telluride (SnTe) thin films were deposited onto Au(1 1 1) substrates from an aqueous solution containing SnCl 2, TeO 2, and C 6H 5Na 3 at room temperature (25 °C) for the first time via electrodeposition route. The electrodeposition of the thin films was studied using cyclic voltammetry, compositional, structural, optical measurements and surface morphology. It was found that the stoichiometric SnTe thin films could be obtained at −0.50 V. The as-deposited thin films were crystallized in the preferential orientation along the (2 2 0) plane. SEM investigations indicated that the shape of thin films could be altered from a spherical particle to a dendritic crystal by increasing the deposition potential. The growth of the dendritic films proceeds via formation of nanoparticles and growth of dendritic crystals on these nanoparticles. The optical absorption studies as a function of deposition time indicated that the band gap of the SnTe thin film increases as the deposition time decreases.