DIAMOND DEPOSITION USING A GRID FILAMENT

A grid tantalum filament of a dimension of 3 x 4 cm(2) was used for di amond synthesis by hot-filament assisted chemical vapour deposition (H FCVD). After proper carburization, the filament could be used for mult i-cycles of deposition. By heating the filament to 2400 degrees C in 8 % CH4 mixed with H-2, diamond has been deposited at rate of about 5 mu m/hour on (100) oriented silicon substrate placed 5 mm away from the filament. By X-ray diffraction (XRD), the structure of the films depos ited in the mixture of CH4 and H-2 was characterized as diamond, while tantalum oxide was found in the presence of oxygen during deposition. The deposited diamond appeared uniform over an area of 2 x 3 cm(2) ob served by scanning electron microscopy (SEM) perhaps due to the stable filament geometry. Raman spectra of these films showed a sharp peak n ear 1332 cm(-1), which indicated the presence of a large amount of sp( 3) bonds in the film. The present grid filament can be scaled-up for l arge area diamond deposition.