CONTINUOUS WAVE VISIBLE LASER ASSISTED DECOMPOSITION OF CR(CO)6 ON A GROWING FILM - INSITU OBSERVATIONS

Direct measurements of volatile products desorbing from the surface of a growing film have been made by molecular beam mass spectrometry. Laser illumination of the substrate-film system induces two distinct regimes of decomposition of Cr(CO)6 over a 300-950 K temperature range. The first of these is a pregrowth regime characterized by limited decomposition of the precursor, and the second is a growth regime in which near-total consumption of Cr(CO)6 occurs. Both regimes are found at all temperatures. Each is characterized by complex, temperature-dependent chemistry which includes desorption of coordinatively unsaturated chromium carbonyl intermediates. CO ejection from the surface appears to involve several channels, including thermal and possibly electronically stimulated desorption. No evidence is found that recombinative desorption of C and O occurs, consistent with results of a separate study showing C and O concentrations in the films to be very low. The implications of these data for current ideas concerning the process of film growth from carbonyl precursors are discussed.