Diamond Deposition Using a Grid Filament

Abstract
A grid tantalum filament of a dimension of 3 x 4 cm² was used for diamond synthesis by hotfilament assisted chemical vapour deposition (HFCVD). After proper carburization, the filament could be used for multi-cycles of deposition. By heating the filament to 2400°C in 8% CH₄ mixed with H₂, diamond has been deposited at rate of about 5 µm/hour on (100) oriented silicon substrate placed 5 mm away from the filament. By X-ray diffraction (XRD), the structure of the films deposited in the mixture of CH₄ and H₂ 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 cm² observed by scanning electron microscopy (SEM) perhaps due to the stable filament geometry. Raman spectra of these films showed a sharp peak near 1332 cm^-l, which indicated the presence of a large amount of sp³ bonds in the film. The present grid filament can be scaled-up for large area diamond deposition.