The aim of this work is to study optical properties of Si nanohills formed on the SiO2/Si
interface by the pulsed Nd:YAG laser radiation. Nanohills which are self-organized on the surface
of Si, are characterized by strong photoluminescence in the visible range of spectra with long wing
in the red part of spectra. This peculiarity is explained by Quantum confinement effect in nanohillsnanowires
with graded diameter. We have found a new method for graded band gap semiconductor
formation using an elementary semiconductor. Graded change of band gap arises due to Quantum
confinement effect.