Effects of implantation energy and annealing temperature on the structural evolution of Ge+-implanted amorphous Si

High-resolution transmission electron microscopy in conjunction with autocorrelation function analysis have been applied to investigate the evolution of structural order in Ge+-preamorphized silicon layers. (0 0 1)Si wafers were preamorphized with 5 and 10 keV Ge+ to a dose of 5 × 1015 ions/cm2. A higher density of embedded nanocrystallites was found to be present in as-implanted amorphous Si layer for 10 keV Ge+ than that for 5 keV Ge+. The densities of embedded nanocrystallites in Ge+-preamorphized Si layer with 5 and 10 keV Ge+ were found to diminish with annealing temperature first then increase. The effects of ion-implantation energy and annealing temperature on the structural evolution in Ge+-implanted amorphous Si are discussed in terms of ion-beam induced annealing and free energy change of the system. The depth dependence on the density of embedded nanocrystallites is attributed to the nonuniform distribution of Ge atoms.