Growth of free-standing diamond films of hemispheric shells

Free-standing diamond films of hemispheric shells were fabricated in a hot filament CVD system by using positive substrate bias. The graphite mold was sputtered with a stainless steel layer of 0.5 um on the surface. During the diamond growth, a thin carbon soot layer with loose structure was first formed on the iron surface and then the growth of a thick diamond film followed. The diamond film could be easily delaminated from the graphite mold due to the weak bonding between the iron-containing carbon soot layer and the graphite substrate. Without the positive substrate bias, the varied distance between the flat hot filaments and the hemispherical substrate in the hot filament CVD system resulted in low nucleation density and non-uniform diamond film. The electron bombardments induced by the positive substrate bias were shown to enhance the diamond nucleation density on the soot-covered surface and thus improved the uniformity of diamond film thickness over the non-flat graphite mold.