We analyse be means of transmision electron microscopy techniques the proce
sses during the initial stages of diamond growth by magnetron sputtering. W
e show that a comparatively high density of C is found as deep as 100 nm in
the Si substrate. The carbon arranges in planar defects in {111} and in {0
01} lattice planes. Our analysis shows that these defects can best be descr
ibed by coherently strained inclusions that resemble hexagonal SiC platelet
s. These can act as seeds for orientated growth of diamond on Si.