Thermal annealing induced redistribution behavior of Au (3MeV, 6.0 x 1015/cm2), implanted into SiO2/Si(100) substrates, was investigated by using Rutherford back-scattering spectrometry and cross-sectional transmission electron microscopy. Sequential annealing at 550 to 750C was found to result in rejection of Au atoms from Si toward the SiO2/Si interface. Above 750C, a significant fraction of the implanted Au atoms was found to back-diffuse into deeper regions, well below the projected range Rp of Au. Direct annealing of a sample at 850C also exhibited a similar anomalous diffusion of Au into deeper regions; well below Rp. However, direct annealing at 1050C was found to result in an enhanced accumulation of Au at a deeper layer. Cross-sectional transmission electron micrographs for the same sample revealed the presence of Au-rich nanoparticles and dislocations, decorated with Au-rich nanoparticles in this region. Trails of Au-Si liquid nanodroplets along with dislocations extending into this region were also observed. The observed enhanced accumulation of Au in the deeper layer was explained as being due to the efficient gettering of diffusing Au atoms at dislocations in this region, together with the migration of Au-Si liquid nanodroplets into it.

Anomalous Diffusion of Au in Mega-Electron-Volt Au Implanted SiO2/Si(100). S.Mohapatra, J.Ghatak, B.Joseph, H.P.Lenka, P.K.Kuiri, D.P.Mahapatra: Journal of Applied Physics, 2007, 101[6], 063542