| Group IV semiconductor (Si, Ge and Sn) nanocrystals were synthesized in dielectric matrixes by ion implantation of the respective species into the matrix to form a supersaturated solid solution and subsequent precipitation by thermal annealing. The resulting structure was characterized by Transmission Electron Microscopy and Raman spectroscopy. It was found that nanocrystals of these materials can be effectively synthesized with diameters in the nanometer range. Ge nanocrystals in SiO{dollar}sb2{dollar} were extensively characterized, particle size distributions were counted from TEM results and were used to compare experimental photoluminescence spectra with theoretical predictions. Unusual nanostructures were formed in samples co-implanted with Ge and Sn and annealed at 600{dollar}spcirc{dollar}C. Raman spectroscopy indicated a possibility of significant alloying of Ge and Sn in these nanostructures. Optical properties of Si nanocrystals in silicon dioxide were investigated by photoluminescence spectroscopy as well. It was found that while Ge nanocrystal system luminescence is mostly due to defects in the matrix produced by ion implantation, Si nanocrystal sample luminescence is due to the Si nanocrystals themselves. The luminescence is above the bulk Si bandgap and supports the quantum confined excitonic luminescence theory. Light emitting devices were fabricated using both systems. Electroluminescence was observed for both Si and Ge, albeit with rather low efficiency, in the {dollar}10sp{lcub}-6{rcub}{lcub}-{rcub}10sp{lcub}-7{rcub}{dollar} range. Electroluminescence from Si nanocrystal containing devices was spectrally similar to photoluminescence from that system, with a band about 800 nm, consistent with electronic excitation of radiative transitions in Si nanocrystals. Cubic nonlinearities were measured for both Ge and Si nanocrystals and found to be {dollar}10sp{lcub}-9{rcub}{lcub}-{rcub}10sp{lcub}-10{rcub}{dollar} esu range. Finally, an interesting interferometric arrangement which has a potential to be useful for investigating nanoscale structures was theoretically described. |
