Low-energy (keV) Si ions were implanted into mask-pattered Si wafers at doses above the amorphization threshold for a variety of implantation conditions (ion dose, energy, temperature) and post-implantation annealing. Precise measurement of the surface swelling (step-height) on the amorphous Si layer was carried out using an atomic force microscope. Thickness and microstructure of the ion-damaged layer was evaluated by transmission electron microscopy measurements. The measured step-height in excess to that contributed by implanted ions showed a cube root dependence on the Si ion dose. The swelling heights studied for 2 different energies of Si ions showed identical step-heights. Implantation at low temperature (77K) showed a reduced step-height, indicating possible contribution of migrated Si atoms in the swelling. It was proposed that excess swelling was caused by the migration and segregation of displaced Si atoms from the bulk to the surface, leaving behind corresponding vacancies in the lattice. Ellipsometric studies of the similarly damaged layer profile provided supporting evidence for the surface segregation of Si atoms over the amorphous layer. A reduction of defect densities in non-polar a-plane GaN films over r-plane sapphire was achieved by using the epitaxial lateral overgrowth approach. A mask pattern was used to produce epitaxial laterally overgrown GaN with a wing region width of about 30µm. Based upon transmission electron microscopy results, the window regions had a stacking faults density of about 106/cm and a threading dislocation density of about 1010/cm2. Both the epitaxial laterally overgrowth Ga-face and the N-face wing regions had a stacking fault density of about 105/cm, and a dislocation density of less than 108/cm2. Cathodoluminescence studies revealed a difference in defect densities between N-faced and Ga-faced wings.

Studies of the Surface Swelling of Ion-Irradiated Silicon - Role of Defects. P.K.Giri: Materials Science and Engineering B, 2005, 121[3], 238-43