DC Plasma CVD Research Articles

地熱発電プラントにおける酸性熱水からのシリカ付着低減のためのa-C:H合成法の検討

In this study, in order to control the effects of hydrogen content and carbon network structure in the outermost layer of a-C:H film on silica scaling adhesion from geothermal steam, the effects of substrate bias during deposition on the hydrogen content and carbon network structure in the outermost layer of a-C:H were investigated. For this purpose, outermost layer and bulk layer of a-C:H were analyzed by surface-enhanced Raman spectroscopy and conventional Raman spectroscopy, respectively. Silica adhesion simulation tests were performed on a-C:H films deposited at substrate biases of -400 and -700 V by using DC plasma CVD using methane gas as a source gas. The a-C:H film deposited at 400 - V had a smaller amount of silica adhesion than that of the a-C:H film deposited at -700 V. The SERS spectra for the a–C:H films showed an increase in the amount of hydrogen and a decrease in the sp2/sp3 ratio in the outermost layer due to a decrease in the substrate bias, and thus we interpreted that these differences caused the decrease of the silica adhesion.

High crystalline quality heteroepitaxial diamond using grid-patterned nucleation and growth on Ir

High crystalline quality heteroepitaxial diamond films were successfully formed by using grid-patterned growth on Ir with dc plasma CVD. The crystalline qualities were evaluated by X-ray diffraction, Raman spectroscopy, and etch pit method. Flat {100} diamond films without unepitaxial crystals were formed through epitaxial lateral overgrowth with grid-patterned nucleation region of 100-μm spacing. Omega-rocking curves using X-ray diffraction showed obvious improvement in tilt and twist components for wider grid-spacing. For 100-μm grid spacing, the lowest tilt and twist were 0.064 and 0.043°, respectively. The average dislocation density of 9 × 106 cm−2 for the diamond film grown with grid spacing of 100 μm was the lowest ever in reported values for heteroepitaxial diamond. A correlation between the distribution of crystallinity and dislocation was discussed from the results of etch pit method, Raman mapping and TEM observation. Finally, the crystallinity was compared with single crystal diamonds grown by CVD and HPHT. By using grid-patterned nucleation, the quality of heteroepitaxial diamond on Ir has reached in the range of homoepitaxial diamond film.

563 パルス化直流プラズマCVD法によるB_2O_3からのcBN薄膜の作成と評価(OS8-3 軽量化,機能化のための表面創製技術,OS8 軽量化,機能化のための界面・表面創製ならびに塑性加工技術)

563 パルス化直流プラズマCVD法によるB_2O_3からのcBN薄膜の作成と評価(OS8-3 軽量化,機能化のための表面創製技術,OS8 軽量化,機能化のための界面・表面創製ならびに塑性加工技術)

Direct Synthesis of TiN and BN Films from TiO<sub>2</sub> and B<sub>2</sub>O<sub>3</sub> by Using Pulsed DC Plasma CVD Method

Direct Synthesis of TiN and BN Films from TiO<sub>2</sub> and B<sub>2</sub>O<sub>3</sub> by Using Pulsed DC Plasma CVD Method

564 パルス化直流プラズマCVD法によるTiO_2からのTiN成膜(OS8-3 軽量化,機能化のための表面創製技術,OS8 軽量化,機能化のための界面・表面創製ならびに塑性加工技術)

564 パルス化直流プラズマCVD法によるTiO_2からのTiN成膜(OS8-3 軽量化,機能化のための表面創製技術,OS8 軽量化,機能化のための界面・表面創製ならびに塑性加工技術)

Investigation of field emission properties of nanorods formed on nanostructured laminated films

The origin of field emission of nano-crystalline diamond/carbon nanowall (ND/CNW) films prepared by DC plasma CVD has been investigated by macroscopic field emission measurements and SEM observation. We found that there is correlation between the field enhancement factors estimated from Fowler–Nordheim plots and shape parameters of the highest nanorods of ND/CNW films deposited at various deposition times. In addition, it was found that emission site densities were almost independent to the deposition time although the deposition time changed the total nanorod densities by over a factor of ten. We concluded that the origin of field emission of ND/CNW films derives from a part of the highest nanorods which mainly grow during CNW deposition.

Study on Temperature Field of Different Substrate Shape in Preparing Diamond Film

Shell diamond film was prepared by DC plasma CVD, and substrate shape had an important influence on the growth of shell diamond film. Simulations of the substrate temperature field have been done respectively when the substrates are convex and concave. The simulation results show that, DC plasma flow more easily on convex substrate than concave substrate, and temperature field of convex substrate is more uniform than concave substrate; uniform temperature field was help to prepare high quality shell diamond film. In this study, shell diamond films were prepared on convex and concave substrate, respectively in experience. The results indicate that the growth of diamond film on convex substrate was better than on concave substrate, and Raman spectrum shows, on the convex substrate, high quality shell diamond film was prepared successfully, and it accords with the simulation results.

Lithium insertion behavior of carbon nanowalls by dc plasma CVD and its heat-treatment effect

Lithium insertion behavior of carbon nanowall (CNW), which is a two-dimensional carbon nanostructures, was studied by cyclic voltammetry and charge/discharge measurements. It was found that CNW had reversible capacities of more than 200 mAh/g with stable charge/discharge potential like that of graphite even though the materials were produced at low temperature of 973 K. It was also found that CNW showed good responses of lithium insertion/extraction reaction because of their small and uniform particle size with well oriented graphene in nanometer scale. Heat treatment of CNW was found to purify the CNW from by-product amorphous carbon phase and the effect on their charge/discharge property was also clarified.

157 パルス化直流プラズマCVD装置によって成膜されたDLC膜の密着性向上(OS3-2最先端金型技術2)

157 パルス化直流プラズマCVD装置によって成膜されたDLC膜の密着性向上(OS3-2最先端金型技術2)

Characterization of Diamond Spherical Shell Thick Film by DC Plasma CVD

Diamond spherical shell thick film was prepared by high power DC-plasma jet CVD. Atom force microscopy, scanning electron microscopy, Raman spectroscopy and roughness-profile-meter were used to characterize microstructure, morphology, impurities and orientation evolution of diamond spherical shell thick film. The results show that, when nucleation begins, grains grow random orientation. The grain size of spherical diamond film prepared is compact, clear, uniform, continuous and no remarkable bigger grain over the whole surface of film. On the growth surface, (100) facets were dominant, and the cross-section SEM indicated that film columnar spreading grew from the substrate surface to the diamond film surface. The roughness of the growth surface was much more than that of the nucleation surface. To adjust some important parameters as methane concentrate, depositing time, and matrix temperature, and high quality diamond spherical shell thick film was deposited.

Optical emission spectroscopic study for diagnostics in high gravity DC-plasma CVD diamond growth

The effect of gravity on materials processing is rather complicated, and a large number of considerably unexpected results due to high gravity or sometimes centrifugation have been reported. The authors have been conducting high gravity diamond thin film growth by the DC-plasma CVD method up to 100 G. The effects of high gravity appeared in the nucleation site density, growth rate, grain size, uniformity, film coverage and morphology. With the increase in gravity, the nucleation site density, growth rate, grain size were all found to be increased, the uniformity and film coverage were improved, and {100} facet became dominant rather than {111} facet. To understand the deposition mechanism in these effects observed in high gravity, a diagnostic apparatus for spectroscopic study of the optical emission from the DC-plasma was developed, and the OES (optical emission spectroscopy) apparatus has been employed in high gravity CVD experiments. The influence of gravity on the most active species in the plasma, such as H, CH, C2 was discussed together with the results from the Raman spectroscopy and X-ray diffraction study.

Development of a New a-Si Photoreceptor Drum by DC Plasma CVD

Development of a New a-Si Photoreceptor Drum by DC Plasma CVD

Development of a New a-Si Photoreceptor Drum by DC Plasma CVD

We developed a new pulse DC plasma CVD layer deposition process for a-Si photoreceptor drums instead of the ordinary high frequency 13.56 MHz plasma process. This has made the layer deposition process speed 2 times faster, minimized by-product powder generation and improved the surface smoothness of the a-Si drum. Through these improvements, we realized production cost reduction. This makes it easier to offer small diameter a-Si drums for tandem color printers, where growth in demand is predicted.

Patterned growth of heteroepitaxial diamond

A novel microfabrication method for heteroepitaxial diamond was developed. Substrates used in present work were heteroepitaxial Ir(001) films deposited on MgO(001) by sputtering method. The Ir surfaces were treated with ion irradiation of CH4/H2 gas by dc discharge using planar diode. Resist masks were patterned on the ion irradiated Ir surface by electron-beam lithography. The mask patterned Ir surface was etched by Ar ion to remove the irradiated surface at non-patterned area using an ion beam etching system. Then, diamond was grown on the substrate by dc plasma CVD method. As a result, we have successfully fabricated the heteroepitaxial diamond on the patterned areas of the substrate in submicron scale.

Morphology dependence of cathodoluminescence spectra of CVD diamond film

Translucent polycrystalline diamond film made by a DC plasma CVD method was investigated with cathodoluminescence spectroscopy and topography. Shift and/or splitting were found in peaks of several luminescence bands, 575, 532, 480, 460, 389, 270 (5RL) and 235 nm (FE), suggesting considerable magnitude of residual stress is present in the film. The behavior of the splitting was different for the different peak, indicating that the symmetries of the associated defects are different. The film after heat treatment at 6 GPa and 1800 °C was found to exhibit new luminescence bands approximately 300 and 500 nm. Splitting of the 575 nm peak was recognized to decrease with the heat treatment, suggesting that the residual stress was reduced.

Synthesis of boron-doped diamond films by DC plasma CVD using a CH 4+CO 2+H 2 gas mixture at lower substrate temperature and formation of an n-Si/p-diamond heterojunction

Diamond films were synthesized by direct current plasma chemical vapour deposition using a CH 4+CO 2+H 2 gas mixture on Si substrates. The optimum deposition conditions were determined. It was found that 0.4 A/cm 2 current density, at applied voltage of 1 kV, resulted in good-quality diamond films. The substrate temperature was 750 K which is considerably lower than the conventional requirement of ∼1100 K. Boron doping was achieved by passing a portion of the gas mixture through boric acid dissolved in methanol. The boron-doped p-type diamond films were deposited on an n-type single crystalline Si substrate and an n-Si/p-diamond heterojunction was fabricated. The p–n junction was characterized in terms of current–voltage ( I– V) and capacitance–voltage ( C– V) measurements.

Wear Resistance of Microextrusion Dies Coated by Diamond-Like Carbon Films

In order to improve the wear resistance of stainless steel extrusion dies, the mechanical properties of diamond-like carbon (DLC) films deposited on SUS630 (17 4PH) substrates have been investigated. It was clearly shown that wear resistance of the dies was significantly improved when high-voltage pulse pretreatment was applied before DLC deposition by DC plasma CVD. The DLC film showed good wear resistance against cordierite clay in an extrusion experiment. Furthermore, in order to strengthen the adhesion between the DLC film and the substrate which were deposited, TiCN films was fabricated as a buffer layer between DLC and SUS630 substrates. It was found that DLC film with high adhesion strength was prepared at relatively low CH 4 gas pressure of 6 Pa.

The large area deposition of diamond by the multi-cathode direct current plasma assisted chemical vapor deposition (DC PACVD) method

Recently, considerable progress in direct current plasma assisted chemical vapor deposition (DC PACVD) of diamond materials has been achieved by adopting a multi-cathode system with cathode temperatures maintained above 2000 °C. This paper presents an overview of the multi-cathode DC plasma CVD method. The plasma operates in the transition region between abnormal glow and arc discharges on a current–voltage curve. Its gas temperature, as estimated by optical emission spectroscopy, is approximately 3000 K. The standard apparatus composed of seven cathodes enables the deposition of diamond films with various film attributes including good optical transparency on substrates of 3–4 inches in diameter.

Use of real-time ion-mass spectrometry and discharge voltage trending for analysis of a-Si DC plasma CVD processes

DC discharge voltage monitoring is a convenient non-intrusive tool for in-line monitoring of plasma-deposited amorphous silicon deposition processes. We discuss the observed variations of the discharge voltage due to (i) changing hydrogen dilution of silane, (ii) etch back of silicon by a hydrogen plasma, (iii) admixing of germane and methane and correlate the results with in situ ion-mass spectroscopy. We suggest that negative ion formation by electron attachment to silane and/or higher-silane species causes the changes of discharge voltage. Time dependences following discharge initiation are discussed in terms of the relative concentrations of silane versus higher-silane species.

Application of scanning tunneling-field emission microscopy for investigations of field electron emission from nanoscale diamond films

A special scanning tunneling-field emission microscope (STFEM) has been used for studying field electron emission from thin nanocrystalline diamond films grown by a DC plasma CVD. These are characterized by turn-on electric fields as low as 3.5 V/μm and by long-term stability of the emission current. Comparing different surface properties (topography, field electron emission intensity, surface potential and local electroconductivity distributions) on a large surface area it was found that, in most cases, emission centre position is not coincident with peaks of the surface profile. It has been noted that the diamond films studied are composed from nano-grained phases distinguished by their physical properties. These are thought to be diamond and graphitic phases. The low-field electron emission from the samples studied is considered to be associated with the presence of these phases. The results of the STFEM mapping have been compared with data on macroscopic current/field field emission characterization. The mechanisms governing low-field electron emission from nanoscale diamond films are discussed.