Browsing by Author "KO, HW"

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LOW-TEMPERATURE GROWTH OF DIAMOND FILMS BY MICROWAVE PLASMA CHEMICAL-VAPOR-DEPOSITION USING CH4+CO2 GAS-MIXTURES
(1994-04-01)
CHEN, CF
;
CHEN, SH
;
KO, HW
;
HSU, SE
;
材料科學與工程學系
Diamond films were deposited on Si substrates at low temperatures using CH4 + CO2 gas mixtures, which are different from conventional mixtures such as CH4 + H-2, CH4 + O2 + H-2 and CO + O2 + H-2. The films were deposited by microwave plasma chemical vapor deposition. High quality diamond films with high growth rates were fabricated at lower temperatures than those used by previous researchers. After 24 h of deposition, the deposited films were characterized using scanning electron microscopy, and their quality was determined by laser Raman spectroscopy and X-ray diffraction. The results showed that, when the microwave power was set at 290 W, well-faceted diamond films were formed in the total gas pressure range 6-25 Torr. The substrate temperatures and the volume ratios [CH4]/[CO2] (in volume per cent) were also changed from 340 to 220-degrees-C and from 60.1 % to 57.3% respectively. The growth rate of diamond films changed from 0.31 to 0.18 mum h-1 in the above growth temperature range. The growth rate of the diamond films increased as the substrate temperature increased. Consequently, we predict that diamond films may be formed using CH4 + CO2 gas mixtures, even at temperatures of less than 200-degrees-C.
MICROWAVE DIAMOND SYNTHESIS WITH HIGH OXYGEN HYDROCARBONS (CARBON-DIOXIDE, OXYGEN)
(1993-12-15)
CHEN, CF
;
CHEN, SH
;
HONG, TM
;
KO, HW
;
SHEU, SE
Our previous study demonstrated that a higher growth rate and improved crystallinity resulted from using CH4-CO(2)s in diamond deposition. The possibility of diamond synthesis using a high oxygen-containing liquid hydrocarbon, dimethyl carbonate (C3H6O3) supplemented by CO2 or 0(2) was therefore explored in the present study. Well-faceted diamond was deposited when the ratios of the respective flow rates for CO2/C3H6O3 and O-2/C3H6O3 were 6%-8% and 1.5%-2.25%. The growth rates of the diamond films, which were of high quality, were 3.6 and 1.7 mu m h(-1) respectively. The diamond films displayed different surface morphology and crystal features in these gas mixtures, i.e. the diamond film possessed more (311) and (100) facets in the O-2-C3H6O3 mixture at a power of 400 W. The diamond film deposited from 6.75% CO2 in C3H6O3 was indicated by the roughness determination not only to possess a higher growth rate but also to attain a smooth surface with a roughness of 0.048 mu m (R(a)). The surface roughness of the diamond film was 0.083 mu m for 2% O-2 in C3H6O3. The intensities of CO, OH and O produced from O-2-C3H6O3 mixtures were observed by optical emission spectroscopy measurements to be greater than those produced from CO2-C3H6O3 mixtures, but the intensities of C(2)d CH showed the opposite trend. This was the main difference between the CO2-C3H6O3 and O-2-C3H6O3 mixtures. Therefore a larger amount of etching agents appears to block the nucleation of diamond in O-2-C3H6O3 mixtures. The complete results of our study, including Raman and X-ray diffraction analyses, are presented here.