Anomalous diffusion of Au in mega-electron-volt Au implanted SiO2/Si(100)

Thermal annealing induced redistribution behavior of Au (3 MeV, 6.0x1015 ions cm-2), implanted into SiO2/Si(100) substrates, has been investigated using Rutherford backscattering spectrometry and cross-sectional transmission electron microscopy (XTEM). Sequential annealing in the temperature range of 550-750 degree sign C has been found to result in rejection of Au atoms from Si toward the SiO2/Si interface. Above 750 degree sign C a significant fraction of the implanted Au atoms has been found to back diffuse into deeper regions, well below the projected range Rp of Au. Direct annealing of a sample at 850 degree sign C also shows a similar anomalous diffusion of Au into deeper regions, well below Rp. However, direct annealing at 1050 degree sign C has been found to result in an enhanced accumulation of Au at a deeper layer. XTEM micrographs for the same sample show 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 have also been observed. The observed enhanced accumulation of Au in the deeper layer has been explained as due to efficient gettering of diffusing Au atoms at dislocations in this region, together with the migration of Au-Si liquid nanodroplets into it