Structural and Electronic Properties of Boron Doped Multiply Twinned Silicon Nanowires

Previous studies of undoped multiply twinned (MT) silicon nanowires (SiNWs) have found these structures to be more stable than the bulk-cut single crystal SiNWs for diameters $<$ 6 nm [1]. The five segments that form the MT-SiNWs result in a strain field, causing the interior region of the MT-SiNW to compress while stretching its exterior. In fact, the distribution of the internal stress field in MT-SiNWs offers a unique opportunity for doping the MT-SiNW, including bi-polar doping, and thus opening doors to novel designs of photovoltaic elements. In this work, we will use highly efficient quantum mechanical simulations based on the semi-empirical Hamiltonian developed in Ref. [2] to investigate the electronic structure of boron doped MT-SiNWs of different diameters. We will first determine the most favorable locations for placing boron atoms by mapping out the stress fields of undoped MT-SiNWs. To understand the doping characteristics, we will compare the local site energies and local electronic density of states of MT-SiNWs of undoped and doped systems, and carry out the calculation for MT-SiNWs of different diameters. 1. Y. Zhao, Phys. Rev. Lett., 91, 035501 (2003). 2. C. Leahy \textit{et al.} Phys. Rev. B74, 155408 (2006).