Preparation and Optical Properties of Substrates with Surface Nanostructure

Abstract

It is experimentally established that thermal annealing of single-crystal substrates of Cd1-xMnxTe (x  0.04-0.45) solid solutions in the air at 920 K results in formation of surface nanostructure (SNS). In so doing, optimal annealing time ta for each molar composition х is determined by empirical expression ta ≈ 35 + 1.3·x, min. Analysis of АFM-topograms shows that SNS is a set of pyramids with the base size 2- 5 µm, which are a combination of smaller 10-100 nm nanopyramids. The result of size quantization in the latter is luminescence band in the energy region ħ larger than the energy gap of material Eg, and its maximum ħωm with increasing х is displaced toward high-energy region. Large half-width of this band is due to considerable spread in dimensions of small nanopyramids. Displacement of maxima of bands of differential optical transmission spectra of substrates with SNS to low-energy region is explained by joint action of light absorption and scattering with participation of free pyramids.