STATES OF SURFACE CARBON DURING DIAMOND GROWTH ON PT

Filament assisted diamond film growth on a Pt foil scratched with diamond paste and on an unscratched Pt foil was examined with X-ray photoelectron spectroscopy (XPS) at selected intervals in the growth process. The samples were transferred between the growth chamber and the ultrahigh vacuum analytical chamber without exposure to air. Before growth, but after exposure to CH4/H2 without the filament on, XPS detected a mixed layer of "graphitic carbon", adsorbed hydrocarbons, and carbon in direct contact with Pt. Once growth with the filament was begun, "graphitic carbon" was converted to or replaced by a stable hydrocarbon deposit. Later in the growth, the hydrocarbon species were replaced by diamond, which grew to form a continuous layer. The unscratched Pt foil showed a similar behavior; however, the diamond formation rate was substantially slower. Diamond growth on Pt differs from previously studied substrates such as Si and Ni in that Pt does not form thick (greater than 50 Å) intermediate layers such as carbide or graphite prior to diamond growth. © 1990.