Quartz Crystal Microbalance Determination of Laser Photochemical Deposition Rates: Mechanism of Laser Photochemical Deposition From the Group 6 Hexacarbonyls

Abstract

ABSTRACTA quartz crystal microbalance has been used to measure the rates of focused uv laser-induced deposition from the Group 6 hexacarbonyls in real time. The experimental configuration employs acwuv laser beam focused onto the microbalance crystal surface at normal incidence to deposit material by decomposition of a metal complex vapor. Simple equations are given for determining absolute deposition rates in terms of the total mass deposited per unit time. Kinetic data obtained with this system have been used to study the mechanism of laser photodeposition from Cr(CO)e, Mo(CO)6, and W(CO)é induced by a frequency-doubled argon ion laser. The rate-determining deposition step involves condensation of products formed upon single-photon dissociation of the metal carbonyls in the gas phase. Additional observations indicate that the adsorbed photoproducts undergo further photo-initiated dissociation on the substrate surface.