IN-SITU DIAGNOSTICS OF FILM THICKNESS AND SURFACE-ROUGHNESS OF DIAMOND FILMS ON A TI-6AL-4V ALLOY BY OPTICAL PYROMETRY

The thickness and surface roughness of diamond films grown on a Ti-6Al -4V alloy in a microwave plasma reactor was measured in situ using opt ical pyrometry. The growing film results in oscillations of the appare nt temperature with time, which can be explained by interference effec ts caused by reflections from the film/air and film/substrate interfac es. The equation governing the transmittance of the diamond/metal syst em has been derived by taking into account the complex index of refrac tion of an absorbing substrate. The apparent temperature was modeled u sing this relation for the transmittance in order to extract the time dependence of film thickness, surface roughness, and the true temperat ure of the substrate. The growth rate was observed to exhibit two regi mes: an initial period of slowly increasing growth followed by a growt h rate that was about 50% higher. The surface roughness increased at a nearly uniform rate but quickly reached a saturation roughness for lo ng deposition times (high surface roughness). The limitation of the mo del for films in the high surface roughness regime is discussed. (C) 1 998 American Institute of Physics.