Enhancement Of Deposition Rate Research Articles

Electrochemistry of conductive polymers: XXXI: Electrochemical preparation of poly( p-phenylene vinylene) in acetonitrile

Studies on electrochemical preparation of poly( p-phenylene vinylene) (PPV) via electrochemical reduction of α,α,α′,α′-tetrabromo- p-xylene have been carried out in acetonitrile. Two intermediate species produced en route to the final products have been identified during the spectroelectrochemical experiments. The coulombic efficiencies of the polymerization reaction were shown to be about 45% with no enhancement in deposition rate noticed when the electrode surface was modified by the PPV film. The cations of the supporting electrolyte played a critical role in determining the morphology of the films. The film thus prepared had poor electroactivity as evidenced by the cyclic voltammetric currents for oxidation and reduction of the polymer and low absorbance of the products produced thereof.

Effects of a Flow Obstacle on the Deposition Rate of Droplets in Annular Two-Phase Flow

Double film extraction technique was used to elucidate the effects of a flow obstacle on the deposition rate of droplets in annular two-phase flow. In the present experiments, the test section was a round tube of 5 mm in inside diameter, air and water were used as test fluids and the flow direction was vertical upward; a short tube that was 2 mm in inside diameter, 3 mm in outside diameter and 20 mm in length was used as a flow obstacle. It was shown that the deposition rate of droplets was markedly increased if the present flow obstacle was concentrically placed in the flow channel. In all the experimental conditions tested, the deposition rates when the flow obstacle was placed were approximately 1.5 times larger than the deposition rates when no obstacle was placed. An empirical correlation was developed to elucidate the influence of flow parameters on the enhancement of deposition rate by the present flow obstacle of simple geometry.

Preparation of Silica Thin Films by Reduction of Aqueous Solution

Silica thin films were first deposited on a poly(ethylene terephthalate) sheet and silicon wafer substrates by the reduction of an aqueous ammonium hexafluorosilicate solution by dimethylamine borane at 323 K. The time course of film growth was measured by X-ray fluorescent (XRF) spectrometry and an enhancement of deposition rate by coating the substrates with catalyst was observed. Characterization of films by X-ray photoelectron spectroscopy (XPS) and infrared (IR) absorption spectroscopy proved that the film consisted mainly of SiO 2 and a surface hydroxyl group. Reactions for film deposition focused on pH shift by reduction of the solution were proposed.

Perfluorooctane Sulfonyl Fluoride as an Initiator in Hot-Filament Chemical Vapor Deposition of Fluorocarbon Thin Films

We have demonstrated the successful use of an initiator species in hot-filament chemical vapor deposition (HFCVD) of poly(tetrafluoroethylene) thin films from the precursor hexafluoropropylene oxide (HFPO). The introduction of perfluorooctane sulfonyl fluoride (PFOSF) in small concentrations allows the enhancement of deposition rates and increased control over film composition. Endcapping by CF3 groups is possible, which may provide benefits such as enhanced thermal stability and higher hydrophobicity for HFCVD films. Conversion of the PFOSF is high, and HFPO utilization efficiency can be increased significantly. The generation of an initiator radical via the pyrolysis of PFOSF may contribute to enhanced nucleation rates during film growth. Initiation and/or nucleation is rate-limiting at low filament temperatures, and mass transport limitations dominate at higher filament temperatures.

Remote Plasma Enhanced Chemical Vapor Deposition of TiOx Films from Titanium Tetraisopropoxide

ABSTRACTTiOx thin films were prepared from titanium tetraisopropoxide (Ti-(O-i-C3H7)4, TTIP) in a remote plasma enhanced chemical vapor deposition (RPE-CVD) using a mixture of hydrogen/oxygen plasma gas. Emission spectra suggested that H-radicals dissociated TTIP molecules in gas phase. By mixing with oxygen, H-radical density was increased with the correlation effect to result in enhancement of deposition rate. Deposition rate was also influenced by OH-radicals. OH-radicals caused deactivation of precursors and hence suppressed Ti-O-Ti bond formation in gas phase. The highest deposition rate of 11 nm/min, which was two orders higher than that for the case of single gas plasma, was achieved in the case of mixture gas ratio of 20% oxygen and 80% hydrogen. Surface reaction due to the heated substrate did not affect the deposition rate though the film structure was remarkably changed. It was demonstrated that for RPE-CVD process, oxygen/hydrogen mixture gas plasma was effective for obtaining high deposition rate, and also H-to-OH radical density ratio was an important factor to control the deposition rate.

Fast growth of amorphous silicon layers by amplitude modulation PECVD

ABSTRACTHydrogenated amorphous silicon has been deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) with a square wave amplitude modulated rf signal of 50 MHz. We studied the dependence of the deposition rate on the modulation frequency, using optical emission spectroscopy and plasma modeling. We observed an enhancement in deposition rate by modulating the plasma. This behavior is explained by the characteristics of the electronenergy distribution during the periodical onset of the plasma. According to a one-dimensional fluid model, high-energy electrons cause a large production of radicals at the onset. The heating occurs over the whole plasma volume, leading to an increase of the homogeneity of the layers. The discharge structure is changed completely. A comparison is made between results obtained at 13.56 MHz and at 50 MHz deposition voltages.

Dry deposition of particles to wave surfaces: II. Wind tunnel experiments

Wind tunnel measurements of particle dry deposition to wavy and flat surfaces were made to estimate the enhancement of deposition rates due to waves on water surfaces. Measurements were made of 4.0 and 6.7 μm uranine particles at wind speeds of 5 and 10 m s −1 to sinusoidal waves with height to length ratios 2 a/ λ=0.1 and 0.03 and to flat surfaces. Results showed that deposition was greatest to the upslope portion of the wave, accounting for 40–45% of the total mass, followed by the trough (30%), downslope (15%), and crest (10–15%). These results generally agreed within experimental variability with modeling predictions ( Zufall et al., 1999). Deposition was enhanced at the upslope due to the effects of particle interception and impaction on the wave. Total deposition to the wave surfaces was greater than deposition to the flat surface for a large majority of the cases. The average increase in deposition to both wave surfaces for both particle sizes and wind speeds over deposition to the flat surface was 80%.

Abnormal High Rate Deposition of TiN films by the Radio Frequency Plasma Jet System

Radio frequency Ar and plasma jets generated in a hollow electrode terminated by a small size Ti nozzle were used for deposition of Ti and films. The regime with low content of reactive gas resulted in an extreme enhancement of deposition rate, more than one order higher than that of Ti. Abrupt increase of the nozzle temperature to >1350°C in this regime is caused by additional thermal energy imparted to the nozzle. Abrupt decrease of the cathode dc self‐bias and simultaneous steep increase of the optical emission from Ti and from ions Ti+, , and Ar+ indicate the transition of the discharge into the RPJ‐arc. This reflects in an enhanced production of Ti and Ti+ which leads to a high rate (≈μm/min) growth of films. The microhardness of films at low nitrogen content is and the film resistivity is 80 μΩ cm. Geometry of the particle transport and the distribution of the, film thickness on substrates confirm a hollow profile of the particle density distribution in the plasma jet.

Effect of Particle Size on the Kinetics of Particle Deposition under Attractive Double Layer Interactions

The effect of particle size on the kinetics of particle deposition in the presence of attractive double layer interactions has been studied theoretically and experimentally. Particle deposition experiments were carried out with several model suspensions of positively charged latex particles and negatively charged glass beads using the packed bed column technique. The model particles used in the deposition experiments covered a wide size range, from 0.08 to 2.51 μm. Experimental deposition rates were compared to theoretical predictions based on a numerical solution of the convective diffusion equation with colloidal, hydrodynamic, and gravitational forces fully incorporated. Theoretical and experimental results reveal that the enhancement in particle deposition rate (i.e,, the deposition rate in the presence of double layer interaction divided by the rate in the absence of double layer interaction) is dependent on particle size. At low ionic strengths, the enhancement in deposition rate passes through a maximum as the particle size increases. This maximum corresponds to particles with a size around 1 μm. It is also concluded that this maximum is determined by the interplay between the size of the particles and the range of the attractive double layer interactions.

Enhancement of the Reactive Deposition Rate of TiN Films at Low Nitrogen Content

films were reactively deposited from a Ti nozzle by an RF plasma jet. At power >100 W the optical emission from Ti measured in the plasma jet channel is significantly higher for 0.4% content of nitrogen in the argon than for pure argon. Extreme enhancement of the deposition rate at 0.4% content of nitrogen with respect to Ti film growth rate was observed. At 180 W the film growth rate of of 1850 nm/min was achieved, which is 30 times higher than the deposition rate of Ti at similar deposition conditions.

Deposition of silicon carbide using the chemical vapor composites process: Process characterization and comparison with RASSPVDN model predictions

In this work, we explore the use of the chemical vapor composites (CVC) process to increase the rates of silicon carbide (SiC) growth on graphite substrates. Large SiC seed particles are used that are deposited by gravity-driven sedimentation. The results show that addition of large (dp = 28 μm) SiC seed particles to a gas phase containing hydrogen and methyltrichlorosilane increases the deposition rate of SiC by amounts substantially higher than that expected from the addition of the particle volume alone. Insight into the mechanism of this deposition rate enhancement is obtained through analysis of SEM photographs of deposits. Growth rates and deposit structures are consistent with the trends predicted by the previously developed random-sphere model of simultaneous particle-vapor deposition (RASSPVDN), which is used here to interpret the data.

Enhancement of deposition rates in the reactive sputtering of silicon exposed to an argon-oxygen plasma

Silicon oxide films were prepared by the reactive radio frequency (rf) sputtering in an Ar-O2 plasma. The deposition rates were measured as a function of oxygen mole fraction in the sputtering gas and sputtering power. It was found that the deposition rate was abruptly enhanced at a critical oxygen mole fraction in an Ar-O2 plasma. This enhancement was attributed to chemical sputtering of the Si target by argon ion bombardment in the oxygen atmosphere. Thus, the reactive sputtering of a Si target in an argon-oxygen plasma was found to consist of three modes, namely, (i) physical sputtering of oxidized target surface, (ii) chemical sputtering, i.e., release of species having very low energy, and (iii) physical sputtering of metallic target surface.

Influence of pressure and radio frequency power on deposition rate and structural properties of hydrogenated amorphous silicon thin films prepared by plasma deposition

The influence of radio frequency (rf) power and pressure on deposition rate and structural properties of hydrogenated amorphous silicon (a-Si:H) thin films, prepared by rf glow discharge decomposition of silane, have been studied by phase modulated ellipsometry and Fourier transform infrared spectroscopy. It has been found two pressure regions separated by a threshold value around 20 Pa where the deposition rate increases suddenly. This behavior is more marked as rf power rises and reflects the transition between two rf discharges regimes (α and γ). The best quality films have been obtained at low pressure and at low rf power but with deposition rates below 0.2 nm/s. In the high pressure region, the enhancement of deposition rate as rf power increases first gives rise to a reduction of film density and an increase of content of hydrogen bonded in polyhydride form because of plasma polymerization reactions. Further rise of rf power leads to a decrease of polyhydride bonding and the material density remains unchanged, thus allowing the growth of a-Si:H films at deposition rates above 1 nm/s without any important detriment of material quality. This overcoming of deposition rate limitation has been ascribed to the beneficial effects of ion bombardment on the a-Si:H growing surface by enhancing the surface mobility of adsorbed reactive species and by eliminating hydrogen bonded in polyhydride configurations.

Enhancement of deposition rate by adding Si2F6 in low-pressure chemical vapor deposition of W using WF6 and H2

The effects of addition of Si2 F6 to low-pressure chemical vapor deposition of W using WF6 and H2 was studied. Adding sufficient Si2 F6 gas enhances the deposition rate (RD ) of W film in the WF6 and H2 system by a factor of 2 over a wide range of deposition parameters, that is, the substrate temperature and the partial pressures of H2, WF6, and Si2 F6. W films deposited under the conditions where the enhancement of RD occurs have a resistivity as low as that of films deposited in the WF6 and H2 system, except for some W films exhibiting β-W structure, and have no Si contamination. The origin of the enhancement of RD by adding Si2 F6 is discussed.

Glow discharge preparation of amorphous hydrogenated silicon from higher silanes

Amorphous hydrogenated silicon has been deposited by plasma decomposition of Si2H6 and Si3H8. A major feature of the process is a deposition rate enhancement of over a factor of 20 compared to monosilane. The resulting films are compositionally similar to monosilane-produced intrinsic a-Si(H), but films deposited at 300 °C substrate temperature show greater photoconductivity. On the basis of our deposition experiments and the known thermolysis chemistry of the silanes, a conjectural model for the deposition process is presented.

The charge on the electron and the value of Planck's constant h

Chromium films were deposited by cooled and hot target magnetron sputtering techniques with unbalanced magnetic field configuration at equal target power density. The dependence of deposition rates of Cr films by the hot target magnetron sputtering on the power density was a non-linear at 27.5–31.5 W/cm2. The optical emission studies indicated the enhancement of deposition rates due to the evaporation of the hot Cr target. The chromium film structure was strongly depended on the factor of «hot target» and the target power density. Cr films were structured to (110) direction in the case of the hot target sputtering, for cooled target configuration – the preferred orientation was changed from (110) to (200) with the power density. Cr+ to Cr ratio and heat flow from the cathode to the substrate influenced on the coating hardness and adhesion. The Cr films with 9.84–12.79 GPa and the non-cracking behavior (up to 15 N) were obtained.