We present a method to form semiconductor nanodots on Si substrates by using ultrathin Si oxide technology and the results on their optical properties. We can form ultra-small semiconductor nanodots with the size of similar to 5 nm and ultra-high density of similar to 10(12) cm (2) on Si surfaces covered with ultrathin SiO2 films of similar to 0.3 nm thickness. We focus on photoluminescence and electroluminescence properties of Ge nanodots embedded in Si. lms. These structures exhibit intense luminescence in the energy region of about 0.8 eV. (c) 2008 Elsevier B. V. All rights reserved.