Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.79: Poster

Thursday, March 17, 2011, 18:00–21:00, P4

Atomic and electronic structure of non-planar Si/SiO₂ interfaces — •Kaori Seino¹, Friedhelm Bechstedt¹, and Peter Kroll² — ¹Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Jena, Germany — ²Department of Chemistry and Biochemistry, University of Texas at Arlington, Arlington, TX, USA

Silicon (Si) nanocrystals (NCs) are promising objects for quantum and photovoltaic devices. However, there are open questions concerning the influence of the embedding amorphous SiO₂ matrix and the NC-matrix interface. In contrast to the planar Si/SiO₂ interfaces with defined crystallographic orientation in layered heterostructures, the NCs are surrounded by almost spherical interfaces with various facets. Here we study the interfacial electronic and bonding properties of Si NCs embedded in SiO₂ by large-scale first-principles calculations. They are based on the density functional theory (DFT) implemented in the VASP code. In our simulations Si NCs with nominal diameters up to 1.6 nm, i.e. systems with more than 1000 atoms, are treated. The atomic geometries are optimized within full quantum-mechanical calculations. The fundamental gap of the NC depends significantly on the matrix. The Si−Si bonds in the NC core are stretched while in the interface regions both types of bonds, stretched and compressed ones, occur. We compute the spatial variation of the electronic structure. The local band edge profiles exhibit different band gaps in the Si NCs and in the matrix region. Significant differences are found comparing embedded Si NCs and planar Si/SiO₂ interfaces.