Synthesis of Ge Nanocrystals Grown by Ion Implantation and Subsequent Annealing

Ge Nanocrystallites (nc-Ge) have been formed by 250 keV Ge⁺⁷⁴ implantation at fluences of [0.5; 0.8; 1; 2; 3; 4]times10¹⁶ atoms/cm² into 300-nm-thick SiO₂ layer thermally grown on p-type Si (100) substrate, followed by thermal treatment at 1000 degC in forming gas atmosphere for 1 hour. All the samples show a broad Raman spectrum with fluences variation as function of the shift Raman. Ge⁺-dose dependence of the Raman intensity at wap 304 cm^-1 for SiO₂ with nc-Ge was observed. The photoluminescence spectra exhibit a maximum intensity around 3.2 eV for the sample implanted at room temperature with a dose of 2times10¹⁶ cm^-2. Infrared spectroscopy shows that the SiO₂ film moved off stoichiometry due to Ge⁺⁷⁴ ion implantation, and that Ge oxides are formed in it. This result is shown as a reduction of GeO_x at exactly the dose corresponding to the maximum PL peak (3.2 eV) and the largest Raman emission at 304 cm^-1. This method is fully compatible with silicon microelectronic technology