Optical reflectivity from highly disordered Si nanowire films

Abstract

In this work we present a study of the reflectivity from highly disordered silicon nanowire films as afunction of the wire size. Arrays of Au-catalyzed Si wires with length and diameter ranging from 0.15–0.2 µm and 30–50nm up to 20–25 µm and 200–250 nm, respectively, were grown on top of eitherSiO2(1 µm)/Si(100) or Si(100) substrates. The integrated total reflection was measured in the 190–2500 nmspectral range. The results show that, increasing the wire size, the optical behavior of theSi wire film can be gradually tuned from that of an optical coating characterized by agraded effective refractive index to that of an ensemble of diffuse optical reflectors. Inaddition, we show how the optical analysis provides some important indications concerningthe structural properties of the nanowires.