Silicon and carbon based nanowires

Nanowires have been an active field of study since last decade. The reduced dimensionality end size allowing electrons can propagate only in one direction has led to quantization which are rather different from the bulk structure. As a result, nanowires having cross section in the range of Broglie wavelength have shown stepwise electrical and thermal conductance, giant Young modulus, stepwise variation of the cross-section etc. Moreover, the atomic structure of nanowires have exhibited interesting regularities which are not known in two or three dimensions. These novel properties of nanowires have been actively explored since last decade in order to find an application in the rapidly developing field of nanotechnology. In the present thesis, we investigated the atomic and electronic structure of a variety of Si and C atom based very thin nanowires starting from linear chain including pentagonal, hexagonal and tubular structures. We found that the C and Si linear chains form double bonds and have high binding energy. Although bulk carbon in diamond structure is an insulator, carbon linear chain is metal and has twice conductance of the gold chain. We carried out an extensive analysis of stability and conductance of the other wires. Our study reveals that Si and C based nanowires generally show metallic properties in spite of the fact that they are insulator or semiconductor when they are in bulk crystal structure. Metallicity occurs due to change in the character and order of bonds.