Bias effects on large area polycrystalline diamond films synthesized by the bias enhanced growth technique

Large area polycrystalline diamond films up to 3 inches in diameter were synthesized on p-type silicon (100) substrate by microwave plasma chemical vapor deposition (MPCVD) using a bias enhanced growth (BEG) technique. Scanning electron microscopy (SEM) reveals half-spherical, amorphous crystalline diamonds of ballas shape were deposited under no bias. Diamond (100) faceted film can be produced at -250 V bias. When the negative bias was increased to -450 V, only (111) faceted faces was produced. Raman spectra obtained using both 514 and 633 nm lasers were analyzed to reveal detailed structure of the diamond films. At -250 V bias, optimal diamond growths were found from Raman spectral analysis. The analysis of C_1S XPS spectrum indicated the large ratio of sp³/s²p at -250 V implying carbon atoms would have more chance to connect into sp³ carbon phase of diamond.