Density functional simulation of chalcogen doped silicon nanowires

In this thesis we report about the first principle investigation of silicon nanowires. Density functional theory has been used to study the electronic properties of pristine and chalcogen doped nanowires. Nanowires with different surface structures and orientations have been considered. We show that substitutional chalcogen atoms have favorable configurations for positions close to the surface of the nanowire. We also show that hyperfine interactions increase at small diameters, as long as the nanowire is large enough to prevent surface distortion which modifies the symmetry of the donor wave function. Moreover, surface effects lead to strong differences in the hyperfine parameters depending on the Se location inside the nanowire, allowing the identification of an impurity site on the basis of EPR spectra.