Comparative study of as-implanted and pre-damaged ion-beam-synthesized ZnS nanocrystallites in SiO2

The semiconducting ZnS nanocrystallites were synthesized by sequential high dose ion implantation of Zn and S in thermally grown SiO2 on Si(100) and subsequent rapid thermal annealing (RTA). Some samples were pre-implanted with Ar ions in order to investigate the influence of radiation induced damage on the Formation of ZnS nanocrystallites. The crystal structure of the ZnS crystallites, their size distribution and the concentration depth profile were analyzed by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) and cross-sectional transmission-electron-microscopy (XTEM). The XRD results indicate, that the phase transition from cubit zinc blende to hexagonal wurtzite structure of ZnS nanocrystallites begins at temperatures below 1000 degreesC. The RBS results show a clear redistribution of Zn and S after RTA annealing. The concentration of Zn is seriously reduced due to strong diffusion towards deeper regions and the surface, while Ar pre-implantation partially suppressed the concentration loss of Zn. Moreover XTEM images show that the concentration profile, the radiation induced damage and the annealing temperature have strong influence on the resulting size distribution of formed ZnS nanocrystals. (C) 2002 Elsevier Science B.V. All rights reserved.