ELECTRONIC PROPERTIES OF NANOMETRIC SEMICONDUCTORS FROM AB INITIO CALCULATIONS

The electronic structure of materials can be tuned by varying the physical size of the crystal. This size dependence of electronic band gap in semiconductor nanocrystals opens fascinating options for the design of device applications without any need of changing their chemical composition. Understanding and exploiting these possibilities requires knowledge and control of the electronic states of nanoscale semiconductor systems. In particular surface states become significantly more important. The goal of this research is to study the electronic properties of semiconductors in the nanometric scale via first principles calculations. Specifically we examine the PbX (X=S, Se, Te) family of semiconductors which is of potential use in electronic (PV) and optoelectronic applications. We report initial results on the atomic and electronic structure of surfaces and thin films of PbSe, which are found to exhibit strong oscillatory dependence on the number of layers, the effect of different ligands adsorbed on the surface on the electronic band structure and the band gap. We also report initial results of first principles calculations on PbSe nanowires.