7513. RF plasma nitriding of Ti-6Al-4V alloy

7513. RF plasma nitriding of Ti-6Al-4V alloy

Clas'sified abstracts 7 5 0 5 - 7 5 1 4 23 7505. Formation of device quality Si/SiO2 interfaces at low substrate temperatnres by remote plasma enhance...

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Clas'sified abstracts 7 5 0 5 - 7 5 1 4 23 7505. Formation of device quality Si/SiO2 interfaces at low substrate temperatnres by remote plasma enhanced chemical vapor deposition of SiO2 We discuss the factors that contribute to the formation of device quality Si/SiO2 interfaces using the low temperature process of remote plasma enhanced chemical vapor deposition (PECVD) to deposit the SiO2 thin films. This includes identification of: (i) the ex situ and in situ processes required for surface preparation prior to film deposition ; (ii) the factors that define the range o f substrate temperatures for thin film deposition ; and (iii) the factors that are important in post-deposition annealing of Si/SiO2 interfaces. The low temperature limit for SiO2 deposition by remote PECVD derives from increased SiOH incorporation, whereas the high temperature and thickness limitations derive from subcutaneous surface reactions in which the Si substrate can be oxidized via process gas/substrate reactions during the deposition process. G Lncovsky et al, J Vac Sci Technol, AS, 1990, 822-831. 23 7506. Ion beam assisted coating and surface modification with plasma source ion implantation Plasma source ion implantation (PSII) is a non-line-of-sight technique which is being developed as an alternative to beamline accelerator technology for ion implantation. The initial development phase of PSII concentrated on implantation of ion species which are gaseous at room temperature (primarily nitrogen ions) and employed a cylindrical vacuum chamber 16 in. high and 14 in. in diameter. A second generation PSII system is being constructed to extend the PSII process to ion beam mixing and ion beam assisted coating modes of operation. The new, larger system (with dimensions 36 x 36 × 36 in.) will feature multiple-array sources for sputter deposition concurrent with ion bombardment. J R Conrad et al, J Vac Sci Technol, A8, 1990, 3146-3151. 23 7507. Radiation-enhanced sublimation of graphite in PISCES experiments Radiation-enhanced sublimation (RES) of graphite leads to potentially high erosion rates in advanced fusion devices (Compact Ignition Tokamak, CIT and the International Thermonuclear Experimental Reactor, ITER) and may be important in the 'carbon blooms' observed in Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET). Erosion rates measured by weight loss are reported for POCO graphite exposed to helium plasmas for a temperature range from 9002000°C, ion energies of 30-300 eV, ion fluxes of l~Sx 10 ~8 cm 2 s-~, densities of 2-10 x 10 ~2cm 3, and electron temperatures of4~10 eV. These are the first data on RES at fusion-relevant particle fluxes. The data show little reduction from a direct linear dependence upon flux. For these conditions, the amount of redeposition and carbon self-sputtering was minimal. Over 1700°C, there is evidence of electron emission from the sample. R E Nygren et al, J Vac Sci Technol, A8, 1990, 1778 1782. 23 7508. Free molecular transport and deposition in cylindrical features A Clausing-like integral equation is derived which applies to both low pressure chemical vapor deposition (CVD) and physical vapor deposition (PVD) in cylindrical contact holes ; i.e. over the full range of sticking coefficients (0-1). A steady state assumption is implicit in the formulation. In the absence of film deposition, the flux to the surface is spatially uniform. Analytical expressions are presented for the initial deposition profiles for PVD (unity sticking coefficient). Numerical inversions of the integral equations provide initial deposition profiles for CVD (low sticking coefficients). Initial deposition profiles exhibit poor uniformity in PVD and high uniformity in CVD, in agreement with empirical evidence. The results provide a test for proposed Monte Carlo simulations which are based on the same assumptions. T S C a l e and G B Raupp, J Vac Sci Technol, B8, 1990, 649~555. 23 7509. Molecular dynamics simulations of low-energy particle bombardment effects during vapor-phase crystal growth: 10 eV Si atoms incident on Si(001)2 × 1 surfaces Molecular dynamics simulations, utilizing the Tersoff many-body potential, were used to investigate the effects of 10 eV Si atom bombardment of a Si lattice with a (001)2 × 1 reconstructed surface. The irradiation events were initiated at an array of points in the primitive surface unit cell. Each event was followed to determine kinetic energy redistribution in the lattice as a function o f time, ion and lattice atom trajectories, and

the nature, number, and depth of residual defects. Surface dimer breaking, epitaxial growth (due to both projectiles and lattice atoms coming to rest at epitaxial positions), and the formation o f residual hexagonal and split interstitials composed of projectiles and/or lattice atoms were observed. There were no residual vacancies. Impact points leading to each of the above results clustered in distinctly different regions of the surface unit cell. Implications of this work for ion-assisted film growth are discussed. M Kitabatake et al, J Vac Sci Technol, A8, 1990, 3726-3735. 23 7510. Morphology and crystal orientation of chromium thin films deposited by ion plating Chromium thin films were deposited by ion plating. The influence of argon gas pressure and substrate bias voltage on the morphology and crystal orientation of the films was investigated by using scanning electron micrography (SEM) and X-ray diffraction. The preferred orientation of the films changed from (110) to (200) with the increase of argon gas pressure. Most of chromium films exhibited columnar structure and the width o f the column became smaller at higher argon gas pressure. The chromium film which was deposited at higher argon pressure exhibited a finer granular structure. The microhardness of the films increased with the increase of bias voltage and argon gas pressure. D D Wang and T Oki, J Vac Sci Technol, A8, 1990, 3163 3167. 23 7511. Synthesis of diamond powder in acetylene oxygen plasma Diamond particles 10-500 nm in diameter were produced by microwaveassisted combustion of acetylene in oxygen. Both premixed and diffusion flame configurations were investigated. A mixture of cubic and hexagonal polytypes of diamond were identified. Larger particle sizes were observed at lower reactor pressure and higher C to O atomic ratios. C to O atomic ratios between 0.83 and 1.0 produced crystalline diamond powder while other ratios produced graphite, soot, and amorphous carbon phases. Diamond formation was not observed when reaction pressures were above 150 tort. W Howard et al, J Appl Phys, 68, 1990, 1247 1251. 23 7512. Effect of substrate temperature on recrystallization of plasma chemical vapor deposition amorphous silicon films The effect of substrate temperature on the recrystallization of plasma chemical vapor deposition amorphous silicon films is investigated. The grain size of polycrystalline silicon films recrystallized at 600°C increases as the substrate temperature decreases. The enlargement in the grain size is attributed to the decrease in the nucleation rate. The nucleation rate is suppressed by an increase in structural disorder of the Si network. Electrical properties of recrystallized films are improved by the increase in the grain size. K Nakazawa and K Tanaka, J Appl Phys, 68, 1990, 1029 1032. 23 7513. RF plasma nitriding of Ti-6AI--4V alloy Titanium alloy ( T i ~ A I ~ V ) samples were nitrided in low pressure (7 mbar) inductive rf (0.5 M Hz) plasmas of nitrogen or nitrogen-hydrogen. The nitriding time was 5 h and the temperatures of the samples during the nitriding process were 470 + 20°C and 420 + 20°C in the discharge and afterglow regions, respectively. The effect o f the sample location in the reactor and of the N2 : H2 ratio in the gas mixture was studied. In the centre of the discharge region e-Ti2N plus 6-TIN phases were formed on top of a solid solution of nitrogen in titanium, ct-(Ti, N). In the afterglow region an ~-(Ti, N) plus e-Ti2N structure were obtained. The effects of nitrogen concentration in the gas mixture and o f the sample location on the microhardness, lattice parameters, composition and structure of the nitrided films are presented and discussed. A Raveh et al, Thin Solid Films, 186, 1990, 241 256. 23 7514. Plasma-enhanced chemical vaponr deposition of thin GeO2, S n O , GeO2-SnO~, and In203 films Thin films of SnOx, GeO2, mixed GexSnyOz, and In203 have been deposited by plasma-enhanced chemical vapour deposition (PECVD) of the methyl compounds Sn(CH3)4, Ge(CH3)4 and In(CH3)3. Indium oxide films have also been prepared from In(thd)3 (thd = 2,2,6,6-tetramethyl3,5-heptanedionato) by PECVD. S Reich et al, Thin Solid Films, 189, 1990, 293 302. 675