Atomic and electron structure of diamond grain boundaries in a polycrystalline film

A polycrystalline diamond film was grown on the polished surface of silicon substrate in H-2-CO-O-2 mixing gas. Atomic and electron structure of grain boundaries in the film was investigated by both high resolution electron microscopy and electron energy loss spectroscopy. CSL boundaries in the film showed characteristic feature in atomic structure; Sigma 9 CSL boundary was parallel not to (221) plane but to (114) plane. A new line which correspond to pi* state was found in addition to major sigma* line in the EELS spectra of the boundary which contained three coordinate atoms. Observed pi* line shows occurred change of a dangling bond (p(z) electron) to pi state. No pi* line appeared in the EELS spectra obtained from boundaries which contained no three coordinate atom such as (111) Sigma 3 boundary.