Effect Of Deposition Pressure Research Articles

Effects of deposition pressure on the microstructural and optoelectrical properties of B-doped hydrogenated nanocrystalline silicon (nc-Si:H) thin films grown by hot-wire chemical vapor deposition

We report on the effects of deposition pressure Pd on the growth and properties of the B-doped nanocrystalline silicon (nc-Si:H) thin films grown by hot-wire chemical vapor deposition (HWCVD) at very high hydrogen dilution of 98.8%. We found that the crystallinity of nc-Si:H or μc-Si:H films is not only determined by hydrogen dilution but also the concentration ratio of atomic H to SiH3 ([H]/[SiH3]) on the growing surface which is varied with deposition pressure Pd. Furthermore, there is a threshold of [H]/[SiH3] ratio which we name as overfull hydrogen (OH). When the [H]/[SiH3] ratio is lower than the threshold OH ([H]/[SiH3]<OH), the crystallinity of the nc-Si:H or μc-Si:H films increases with increasing [H]/[SiH3] ratio. But when the [H]/[SiH3] ratio is higher than the threshold OH ([H]/[SiH3]>OH), the crystallinity decreases with increasing [H]/[SiH3] ratio. Finally, the high conductivity of 4.22Scm−1 of the B-doped nc-Si:H thin film deposited at 15Pa is obtained.

Effect of deposition pressure on the adhesion and tribological properties of a-CN x H films prepared by DC-RF-PECVD

Hydrogenated carbon nitride (a-CNxH films) was deposited on n-type single-crystal Si (100) by direct current radio frequency plasma-enhanced chemical vapor deposition (DC-RF-PECVD), under the working pressure of 5.0–17.0 Pa, using the CH4 and N2 as feedstock. The composition and surface morphology of the a-CNxH films were characterized by means of Raman spectroscopy and atomic force microscopy, while the Young’s modulus, elastic recovery, adhesion strength, and tribological properties were evaluated using nano-indentation, scratch test and friction test system. It was found that the surface roughness and Raman spectra peak intensity ratio ID/IG of the films increased with the increase of working pressure, while the Young’s modulus, elastic recovery and adhesion strength of the films significantly decreased. Moreover, the tribological properties of the films also varied with the working pressure. The wear life sharply increased with the increase of working pressure from 5.0 Pa to 7.5 Pa, further, an increase in the deposition pressure led to a gradual decrease in the wear life, consequently, the a-CNxH film deposited at 7.5 Pa exhibited the longest wear life. The deposition pressure seemed to have slight effect on the average friction coefficients, whereas the surface roughness and adhesion strength have deteriorated with increasing deposition pressure.

Effect of Deposition Pressure on the Morphology and Structural Properties of Carbon Nanotubes Synthesized by Hot-Filament Chemical Vapor Deposition

Hot-filament chemical vapor deposition has developed into an attractive method for the synthesis of various carbon nanostructures, including carbon nanotubes. This is primarily due to its versatility, low cost, repeatability, up-scalability, and ease of production. The resulting nano-material synthesized by this technique is dependent on the deposition conditions which can be easily controlled. In this paper we report on the effect of the deposition pressure on the structural properties and morphology of carbon nanotubes synthesized by hot-filament chemical vapor deposition, using Raman spectroscopy and high-resolution scanning electron microscopy, respectively. A 10 nm-thick Ni layer, deposited on a SiO2/Si substrate, was used as catalyst for carbon nanotube growth. Multi-walled carbon nanotubes with diameters ranging from 20-100 nm were synthesized at 500 degrees C with high structural perfection at deposition pressures between 150 and 200 Torr. Raman spectroscopy measurements confirm that the carbon nanotube deposit is homogeneous across the entire substrate area.

Effects of deposition pressure on the properties of transparent conductive ZnO:Ga films prepared by DC reactive magnetron sputtering

Gallium (Ga)-doped zinc oxide (ZnO:Ga) transparent conductive films were deposited on glass substrates by DC reactive magnetron sputtering. Effects of deposition pressure on the structural, electrical and optical properties of ZnO:Ga films were investigated. X-ray diffraction (XRD) studies show that the films are highly oriented with their crystallographic c-axis perpendicular to the substrate almost independent of the deposition pressure. The morphology of the film is sensitive to the deposition pressure. The transmittance of the ZnO:Ga thin films is over 90% in the visible range and the lowest resistivity of ZnO:Ga films is 4.48×10 −4 Ω cm.

Deposition pressure effects on material structure and performance of micromorph tandem solar cells

Tandem solar cells represent an elegant way of overcoming the efficiency limits of single-junction solar cells and reducing the light-induced degradation of amorphous silicon films. Stacked structures consisting of an amorphous silicon top cell and a microcrystalline silicon bottom cell allow a good utilization of the solar spectrum due to the band gap values of the two materials. These devices, firstly introduced by the IMT research group, were designated as “micromorph” tandem solar cells. To better exploit this concept, it is important to tune parameters like the band gaps and the short-circuit currents. In this work, we have realized micromorph tandem solar cells on Asahi U-type TCO-covered glass substrates. The intrinsic layer of both the amorphous top cell and the microcrystalline bottom cell is grown by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) at 100 MHz at low substrate temperature (150 °C). Finally, a ZnO reflector and a metal contact complete the structure. No intermediate optical mirror between the two cells is used at this stage. Undiluted a-Si:H, with reduced band gap when compared to H 2-diluted amorphous silicon, is used as absorber layer in the top cell. As for the bottom cell, the high-pressure–high-power regime (up to 267 Pa–80 W) has been explored aiming at growing high-quality microcrystalline silicon at large deposition rates. The effect of the structural composition of the microcrystalline absorber layer on the current–voltage characteristic and spectral response of tandem devices has been investigated. An efficiency of 11.3% has been obtained with short-circuit current densities around 13 mA/cm 2, open-circuit voltages ∼1.34 V and fill factors ∼66%.

Influence of deposition pressure on the structural mechanical and decorative properties of TiN thin films deposited by cathodic arc evaporation

TiN coatings can be obtained in a relatively wide range of compositions around stoichiometry. Changing the stoichiometry around the 1:1 composition broadens the spectrum of colors and can modify the mechanical properties as compared with those of stoichiometric TiN. In this work, we present the deposition of TiN coatings by using a metallic Ti cathode and varying the nitrogen partial pressure in a cathodic arc evaporation reactive process. The composition, crystalline structure, hardness and color of the different samples are characterized, and the effect of deposition pressure is discussed. The hardest coatings were deposited in the interval of deposition pressures between 5 and 20×10 −3 mbar. From the reflectance spectra in the visible range, a dominant wavelength of 581–582 nm is found for all the TiN samples, very close to that of the pure gold reference spectrum (579 nm) with purity colors that increase with the deposition pressure from 0.67 to 0.84 and approaches the color purity measured for the pure gold reference (0.91).

Effect of deposition pressure on microstructure and tribological behavior of MoS x /MoS x -Mo nanoscale multi-layer films

MoSx/MoSx-Mo multi-layer films consisted of several bilayers and a surface layer on steel substrate were deposited by d.c. magnetron sputtering at different deposition pressures. Each bilayer contained a MoSx layer with 80 nm in thickness and a MoSx-Mo composite layer with 20 nm in thickness. With the increase of deposition pressure, the perpendicular orientation of the basal plane prevailed while the parallel orientation decreased. The tribological properties of the multi-layer films were investigated by using a ball-on-disk tribometer both in vacuum and in humid air. The multi-layer film deposited at 0.24 Pa had a compact, consistent layered structure with high intensity of (002) plane and low S content compared to the others deposited at 0.32 and 0.40 Pa, and showed the lowest friction coefficient and wear rate in humid air.

Effect of Deposition Pressure on Switching Field Distribution of CoPtCr–SiO$_2$Perpendicular Magnetic Recording Thin Film Media

We studied the effects of the deposition Ar pressure on the switching field distribution (SFD) of Tb/Pt/Ru/CoPtCr-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> perpendicular media. In this study, we describe a simple method for obtaining parameters of the SFD such as the standard deviation (SD) while taking the effect of demagnetizing field into account. The SFD changed its character greatly with the change of Ar pressure. The differences in the SD of the SFD of various samples may originate from the variation of intergranular exchange and the demagnetizing field due to different Ar pressure

The Effects of Deposition Pressure on the Optical and Structural Properties of d.c. PECVD Hydrogenated Amorphous Carbon Films

A direct-current plasma enhanced chemical vapour deposition (PECVD) system was designed and built in-house for the deposition of hydrogenated amorphous carbon(a-C:H) thin films. In this work, a-C:H thin films prepared using this system at different deposition pressures were studied. The influence of deposition pressure on the deposition rate, energy gap, bonded hydrogen content and structure of the film has been investigated. The characterization techniques were determined from optical transmission spectroscopy, Fourier transform infrared spectroscopy and Xray diffraction measurements. The results demonstrated that the deposition pressure had strong influence on the deposition rate, optical energy gap and the bonded H content in the film. Evidence of crystallinity was observed in films prepared at low deposition pressure.

Phosphorus doping and deposition pressure effects on optical and electrical properties of polysilicon

The optical and electrical properties of amorphously deposited and then post-crystallized silicon films are studied as a function of the deposition pressure and the phosphorus doping. Amorphous silicon films are deposited in a high pressure regime by SAPCVD (Sub-Atmospheric Pressure Chemical Vapour Deposition) to study the effect of the deposition pressure. They are also deposited in a low pressure regime by LPCVD (Low Pressure Chemical Vapour Deposition) to study the effect of a low phosphorus doping. Both types of amorphous films are then crystallized in the solid phase at 600 °C. Using different optical and electrical characterization techniques, the beneficial effect of a high pressure as well as of a weak phosphorus doping on the decrease of the defect density is highlighted. These results give some ways to improve the quality of polysilicon enough to be used in photovoltaic or in thin film electronic devices.

Effect of deposition pressure on microstructure and properties of hydrogenated carbon nitride films prepared by DC-RF-PECVD

Hydrogenated carbon nitride (a-CN:H films) were deposited on n-type (1 0 0) silicon substrates making use of dual direct current radio frequency plasma enhanced chemical vapor deposition (DC-RF-PECVD), at working pressure of 2–20 Pa, using a mixed gas of CH 4 and N 2 as the source gas. The growth rate, composition, bonding structure of the deposited films were characterized by means of XPS and FTIR, and the mechanical properties of the deposited films were investigated by nano-indentation test. It was found that the parameters for the DC-RF-PECVD process had significant effects on the growth rate, structure and properties of the deposited films. The growth rate of the deposited films increased at first with increasing deposition pressure, then saturated with further increase of the deposition pressure. The N/C ratio inside the deposited films increased with increasing working pressure except that it was as much as 0.50 at a working pressure of 5.0 Pa. The nano-hardness of the films decreased with increasing deposition pressure. CN radicals were remarkably formed in the deposited films at higher pressures, and their contents are related to the nitrogen concentrations in the deposited films.

Effects of Deposition Pressure on Properties of Carbon-Doped Silicon Oxide Low Dielectric Constant Films

Carbon-doped silicon oxide [SiO(C,H)] dielectric films have been prepared by the plasma-enhanced chemical vapor deposition technique from trimethylsilane in an oxygen environment. The process pressure was varied from and its effects on the properties of these films have been investigated. The films were also annealed at different temperatures from to determine their thermal stability. The thickness, refractive index, dielectric constants, infrared absorption, and surface morphology of the as-deposited and annealed samples were characterized. The dielectric constants of the as-deposited films were found to decrease initially with increasing process pressure and nearly saturate at pressures beyond . Dielectric constant as low as 2.86 has been obtained from the as-deposited film at process pressure. Lower refractive indexes were also obtained for films deposited at higher pressure. There are no significant changes to the properties of the films upon annealing at temperatures up to , which is beyond the current highest processing temperature for back end of the line structure of around . However, beyond that annealing resulted in a sharp increase in the dielectric constants of the films, attributed to the decomposition of and bonds.

Sputtering power and deposition pressure effects on the electrical and structural properties of copper thin films

We investigated the effects of sputtering power and deposition pressure on the electrical and structural properties of dc magnetron sputter-deposited copper films on p-type silicon grown at room temperature. Results from our experiments showed that the deposition rate of the copper films increased proportionally with the sputtering power. Sputtering power also affected the structural properties of the copper films through the surface diffusion mechanism of the adatom. From the scanning electron microscopy surface analysis, the high sputtering power favored the formation of continuous film. The poor microstructure with voided boundaries as a result of low sputtering power deposition was manifested with the high resistivity obtained. The deposition rate was found also depending on the deposition pressure. The deposition pressure had the contrary effect on structural properties of copper films in which high deposition pressure favored the formation of voided boundaries film structure due to the shadowing effect, which varied with different deposition pressure.

Statistical analysis of the effect of deposition parameters on the preferred orientation of sputtered AlN thin films

A response surface statistical method was used to study the effects of deposition pressure, power and substrate temperature on the degree of preferred orientation of aluminum nitride films grown on Si (111) by dc magnetron sputtering. The AlN films were deposited at gas pressures ranging from 0.66 to 1.33 Pa, substrate temperature from 300 to 400 °C and power from 100 to 200 W. The degree of preferred orientation was evaluated and quantified using two-dimensional X-ray diffraction, which provides information on the out of plane (002) crystal alignment. The statistical method yielded a surface response curve in the parameter space and a correlation equation between the deposition parameters was obtained. Substrate temperature showed no significant effect upon texture quality for the temperature range studied. A surface response graph as a function of pressure and power was obtained. The main factor affecting texture quality was found to be a pressure–power interaction. The possible mechanisms that contribute to such correlation are discussed. Our best films yielded a rocking curve with full width at half maximum of 6.3°.

Structural and multiferroic properties of BiFeO3 thin films at room temperature

BiFeO 3 thin films have been prepared on Pt∕TiO2∕SiO2∕Si substrates under various oxygen pressures of 0.15–0.005Torr at a temperature of 450°C by pulsed-laser deposition. The effects of deposition pressure on their crystal structure and multiferroic properties have been investigated at room temperature. X-ray diffraction analysis (θ-2θ scans and 2-dimensional scans) shows that the BiFeO3 thin films consist of perovskite single phase with tetragonal crystal structure and space group P4mm. The c-axis lattice constant decreases (4.062–4.006Å) and c∕a ratio of the films decreases from 1.032 to 1.014 with a decrease in the oxygen pressure. The surface roughness and grain size of the films depend dramatically on oxygen pressures. The dielectric constant of the films decreases with decreasing oxygen pressure. The film deposited at 0.05Torr shows a stable current density and well-saturated hysteresis loop with twice the remanent polarization (2Pr) of 136μC∕cm2 and coercive field (2Ec) of 109kV∕cm. The BiFeO3 thin films also show the saturated weak ferromagnetic hysteresis loops with a small remanent magnetization.

Growth of cubic SiC thin films on Si(001) by high vacuum chemical vapor deposition using 1,3-disilabutane and an investigation of the effect of deposition pressure

We have deposited cubic SiC thin films on Si(001) substrates by high vacuum chemical vapor deposition (CVD) using a single molecular precursor of 1,3-disilabutane (DSB) at various temperatures (600–1000 °C) and pressures in the range of 1×10−6–1×10−5 Torr. A single-crystalline cubic SiC thin film with stoichiometric composition can be obtained under deposition conditions of 900–1000 °C and 4.0–6.5×10−6 Torr. However, on increasing the deposition pressure and decreasing the growth temperature to 1×10−5 Torr and 600 °C, respectively, the film became polycrystalline. The effect of deposition pressure on the film growth rate and crystallinity was also studied. Based on the experimental results from x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy, and transmission electron diffraction, the best SiC film was grown at 900 °C and 6.5×10−6 Torr of DSB at a maximum growth rate of 0.1 μm/h. The thicknesses of as-grown films were determined by cross-sectional SEM and Rutherford backscattering spectroscopy. Two different activation energies for cubic SiC film formation were obtained from Arrhenius plots. The deposition temperatures and pressures used in this study are lower by as much as 200 °C and a factor of 102, respectively, compared with those grown by conventional CVD methods.

Effects of Deposition Pressure on the Properties of a Low-Dielectric Constant Cyclohexane-based Plasma Polymer

The effects of deposition pressure on the properties of cyclohexane-based plasma polymer (CHexPP) thin films were investigated. Deposition of CHexPP thin films at higher deposition pressures was associated with lower deposition rates and produced thin films with lower k-values, lower thermal stabilities and higher etching rates. It is considered that the higher deposition pressure decreases the energies of the charged reactive species generated by the plasma from the precursor molecules, resulting in less dense and less well cross-linked plasma polymer thin films.

Effect of deposition pressure on bonding nature in hydrogenated amorphous carbon films processed by electron cyclotron resonance plasma enhanced chemical vapor deposition

Electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) process of hydrogenated amorphous carbon (a-C:H) thin films on Si(100) substrate was investigated with varying CH4 flow rate, radio frequency (RF) self-bias voltage and deposition pressure. A continuous a-C:H film was formed on a Si substrate only when emission intensity ratio of CH to Hb in the plasma was larger than 0.66. Raman characteristic peaks of the a-C:H films were changed from two distinct bands into single broad band when deposition pressure increased from 3 to 36 mTorr. The G band width and the Fourier transform-infrared (FT-IR) spectra indicated that the change in Raman characteristic peaks was associated with the change of bonding nature in a-C:H film from low hydrogen containing film to high hydrogen containing film. The change of bonding nature with increasing deposition pressure was due to the lower impact energy of bombarding ions and the saturation of fragmented CH ions by hydrogen atoms in plasma at high deposition pressure in ECR-PECVD. © 2000 Elsevier Science S.A. All rights reserved.

Effects of deposition pressure on structure and hardness of amorphous carbon nitride films synthesized by shielded arc ion plating

Amorphous carbon nitride (a-C:N) films were synthesized by shielded arc ion plating (SAIP) at the wide pressure range of 0.01–30 Pa. It is essential to prepare a-C:N films at pressures below 0.1 Pa or apply negative voltages to substrates at pressures below 1 Pa for fabricating hard films. Appropriate N2+ ion bombardment increases compressive stresses and promotes formation of fourfold coordinated carbon micro-networks in a-C:N films. N/C ratios of these hard films were <0.26 and N atoms substituted for C sites in amorphous carbon networks. On the other hand, in order to raise N/C ratios of a-C:N films, it is necessary to prepare the films at as high a pressure as possible. The maximum N/C ratio was 0.51 at 30 Pa with no substrate bias. Even this value is much lower than 1.33 of hypothetical C3N4. CN radicals were remarkably formed in the plasma at higher pressures and related to nitrogen concentrations in a-C:N films. CN radicals were considered to act as precursors of aromatic plain carbon–nitrogen networks, and a-C:N films prepared at higher pressures were very soft. Conclusively, three-dimensional carbon nitride structures with high hardnesses and high nitrogen concentrations have not achieved at the same time by such PVD processes as SAIP.

Spectroscopic studies of hydrogen related defects in CVD diamond

Thin diamond films prepared by the hot filament chemical vapour deposition (HFCVD) method at various deposition pressures have been characterized using a variety of spectroscopic techniques. Interpretation of the spectral details have provided useful information about the nature of the films. Deposition pressure appears to affect the quality of the diamond films which is reflected in terms of the position and width of the characteristic Raman peak of diamond. Raman spectra of the films prepared at low deposition pressures showed the presence of a sharp peak at ∼1332 cm−1 characteristic of theT 2g mode of diamond. The study of the effect of deposition pressure on the diamond growth, shows that in the range between 20 torr and 60 torr, there is little effect on the width and the shift of the 1332 cm−1 Raman peak. However, at higher pressures the peak showed a blue shift and was considerably broadened. These studies indicate the development of strain in the lattice due to the introduction of unetched hydride layer, at higher deposition pressures, as well as distortions in the lattice leading to partial lifting of the degeneracy of theT 2g mode. A broad band corresponding to the non-diamond phase (which exists at the grain boundaries, interface or as inclusions inside the grain), which can be attributed to the effect of hydrogen impurity creeping into the lattice at higher deposition pressures is also observed. SEM and XRD patterns have confirmed the dominance of diamond phase in these films.