Grain boundary diffusion activation energy derived from surface roughness measurements of aluminum thin films

Surface roughness measurements of 600-nm-thick aluminum thin films deposited on oxidized silicon substrates have been made by Verkerk and Raaymakers [Appl. Opt. 25, 3602 (1986)]. Here, their data are shown to yield an Arrhenius activation energy of 0.55±0.05 eV/atom. This activation energy is found for T>0.5 Tm, where T is the substrate temperature during deposition and Tm is the melting temperature of aluminum. The regime T>0.5Tm is known to correspond to zone 3 of the structure zone model (SZM) developed by Movchan and Demchishin [Fiz. Metal. Metalloved. 28, 653 (1969)]. The activation energy for grain growth within zone 3 is attributed primarily to bulk or grain boundary diffusion. The activation energy derived from the data of Verkerk and Raaymakers agrees well with the known activation energy for grain boundary diffusion in bulk aluminum, 0.56 eV/atom.