Optical properties of silicon nanostructures

Abstract

The electronic structures and the imaginary part of the dielectric function ${\mathrm{\epsilon }}_2$(ω) for Si nanostructures simulated by spherical clusters are studied. By comparing the ${\mathrm{\epsilon }}_2$(ω) curves of Si nanostructures with that of bulk Si, the evolution of the optical properties of Si nanostructures with the increase of the cluster size is presented. It is shown that, for Si nanostructures, a peak in the ${\mathrm{\epsilon }}_2$(ω) curve, which has no counterpart in the case of bulk silicon, appears in the lower-energy region. With the increase of the size of the Si cluster, the peak shifts towards lower energy, and its intensity decreases until it vanishes in the case of bulk Si. By comparing the density of states of the nanostructures with that of bulk silicon, the origin of this peak in the ${\mathrm{\epsilon }}_2$(ω) curve is discussed.