Early stages of diamond film deposition on molybdenum substrates using
dc arc discharge in CH4/H-2 gas mixtures were studied by in situ meas
urements of optical reflectivity of growing film. Ultrafine diamond gr
it of almost-equal-to 200 angstrom size was used for seeding to increa
se nucleation density up to 2 X 10(9) cm-2 and to produce smooth thin
films. Evolution of He-Ne laser beam reflection at 0.63 mum wavelength
is described in terms of Mie scattering by nonabsorbing dielectric sp
heres in the case of nucleated film and of light interference in the s
ystem of continuous diamond film on a metal substrate. During the depo
sition process the growth rate passes through a minimum at the moment
when a minimum roughness is supposed to be achieved.