The reactivity of CH3CH2AuP(CH3)3 and CH3AuP(CH3)3 is investigated on silicon, chromium, copper, PMDAODA polyimide, and silicon dioxide surfaces at temperatures ranging from 25 to 400 °C in an ultrahigh-vacuum chamber. By exploitation of the advantages of kinetically controlled reaction conditions and atomically clean surfaces, high-purity gold films are deposited at temperatures as low as room temperature. The surface reaction generating elemental gold is subject to an unusual level of control. Excursions to only moderately higher temperature serve to tune the process from one which is completely selective for metal and semiconductor surfaces to one which provides blanket deposition. Enhanced selectivity, allowing the discrimination between different metal substrates (e.g. Cr versus Cu or Au) is achieved by prior exposure of the substrate surface to inhibition agents such as P(CH3)3 and BF3. The inhibition by BF3 is essentially complete for deposition on Cr at 25 °C but is reversed by relatively mild heating of the substrate to 350 °C. © 1994, American Chemical Society. All rights reserved.