Gas phase versus surface contributions to photolytic laser chemical vapor deposition rates

The rate of cw photolytic laser chem. vapor deposition (LCVD) of Pt was measured for l = 350 nm as a function of light intensity and metalorg. vapor pressure. The growth of the metal films was studied in situ and in real time by monitoring optical transmission. At low intensities the transmitted light decreases monotonically with time, and the LCVD process is photolytic with its rate limiting step in the surface adlayer. At higher intensities 2 distinct time domains were obsd. An improved method for distinguishing between adlayer and gas-phase limiting processes is demonstrated. These observations are confirmed by studying the photolytic deposition rates while varying the thickness of the adlayer.