The role of gas adsorption in ion-beam-induced deposition of gold

Abstract

Gold films were deposited on quartz crystal microbalances (QCM) by decomposing C7H7F6O2Au [dimethyl gold hexafluoroacetylacetonate, or DMG(hfac)] with a 5-keV argon-ion beam. A model for ion-beam-induced deposition is presented which relates the net deposition yield to the gas adsorption, the decomposition cross section, and the sputtering yield. The deposition rate was measured in situ as a function of ion current, gas pressure, and substrate temperature using the QCM. The deposition yield (mass deposited per incident ion) increased with increasing gas pressure and decreasing substrate temperature. The QCM was also used to measure the adsorption of DMG(hfac). The results demonstrated that the variation in deposition yield with temperature and pressure was proportional to the number of DMG(hfac) molecules adsorbed per cm2. Based on the observed correlation between deposition yield and adsorption, a decomposition cross section for 5-keV argon ions of 2×10-13 cm2 was estimated.