In Situ Real Time Observation of Chemical Vapor Deposition Using an Environmental Transmission Electron Microscope

Material synthesis by chemical vapor deposition (CVD) in a number of material systems has been investigated in real time using an environmental transmission electron microscope (ETEM) with 3.8 Å resolution. Here, we will focus on two metal / insulator systems. Al CVD onto SiO2 from trimethyl amine alane and Au CVD from ethyl (trimethylphosphine) gold (I), also onto SiO2. For Al deposition, dendritic growth was observed for all pressure / substrate temperature combinations investigated for growth on untreated SiO2. Subsequent to reaction of the substrate surface with TiC14, almost immediate continuous Al film growth was observed. Growth rates for the Al film could be measured in situ by monitoring the evolution of the growth front at the Al/vacuum interface. In this system, very little enhancement in the metal film growth rate was observed as a consequence of electron beam irradiation for continuous films grown after TiCl4 pretreatment.. This dramatically contrasts with the case of Au CVD investigated. In this instance, growth rate enhancements of up to 150 times were observed during electron beam irradiation as compared to purely pyrolytic decomposition of the precursor on the insulator surface. This growth rate enhancement decreased monotonically with substrate temperature. We surmise that this effect is related to the ratio of precursor surface residence time prior to ecomposition to the probability of collision from the impinging electron beam.