Nanosized crystallites have been synthesized in the Si and SiO2/Si structures by means of As (170 keV, 3.2 x 10(16) cm(-2)) and In (250 keV, 2.8 x 10(16) cm(-2)) implantation at 25 degrees C and 500 degrees C and subsequent annealing at 1050 degrees C for 3 min. The Rutherford backscattering, transmission electron microscopy, and photoluminescence techniques were used to analyse the impurity distribution as well as the structural and optical characteristics of the implanted layers. It was found that oxidation of samples before thermal treatment significantly reduced the As and In losses. A broad band in the region of 1.2-1.5 mu m was detected in the photoluminescence spectra. The highest photoluminescence yield for the samples after "hot" implantation and annealing was obtained. Anodic oxidation of the implanted samples before annealing results in the additional increase of photoluminescence yield.