DIAMOND HOMOEPITAXY BY HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

Diamond homoepitaxy grown by microwave plasma chemical vapor deposition (MWCVD) yields optimal results at a CH4 concentration in H-2 of 6%. In the present work we report on successful homoepitaxial diamond growth using hot-filament CVD (HFCVD). However, in contrast to results obtained by MWCVD, we show that optimal growth occurs at lower methane concentrations of 0.5-1%. A conventional HFCVD reactor was used to deposit diamond onto [100] and [111] oriented natural diamonds, using CH4 in H-2 mixtures varying from 0.5% to 4%. The thicknesses of the grown films were of the order of several micrometers. The results show good homoepitaxy when low CH4 concentrations are used. Films grown under such conditions exhibit good ion channeling (x(min)=0.13, for 320 keV H+), reflection high-energy electron diffraction patterns of single-crystal diamond, smooth morphologies and optical transparency. With increasing methane concentration the film properties degrade. The crystalline quality on both (100) and (111) faces deteriorates, and on (111) graphitization takes over.