Germanium Based Nanotubes: Fact Or Fiction?

Unlike carbon nanotubes, nanostructures of Ge, a group IV semiconductor, have not been fully explored. In particular, there is limited data available on Germanium-based nanotubes. The aim of this thesis is to explore the structural and electronic properties of Germanium based nanotubes and their potential future electronic applications. We have thus performed a systematic ab initio study of the electronic and geometric structures of three different types of single-walled SiGe and GeC nanotubes in armchair (n, n) and zigzag (n, 0) (3<n<11) configurations using hybrid density functional theory and the finite cluster approximation. Also we provide the detailed analysis of pure Si (armchair, zigzag and chiral) and Ge nanotubes in the armchair and zigzag format with similar dimensions. The Gaussian '03 suite of programs was used for all computations which involved full geometry and spin optimizations. A detailed stability investigation of the topologically similar nanotubes with dependence of the electronic band gaps on the tube diameters, energy density of states, and dipole moments have been carried out. Using the Mulliken charge analysis, charge density distribution along the tube lengths is also calculated. In depth structural analysis and distribution of molecular orbitals are also reported. The spatial positions of the atoms, ionicity, and curvature are the primary governing factors in the determinations of the stabilities and the electronic behavior of the nanotubes. The interesting findings from this detailed study of Ge based hybrid nanotubes can be useful to fabricate and manipulate the future nano-electronic devices.