Numerical Study of Effect of Surface Potential on Transport Properties of Bi Nanowires

We numerically investigated the effect of the surface on the transport properties of Bi nanowires. The effect of the surface was modeled using the surface potential. The energy shift in each band due to the surface potential was calculated by a perturbation method. The effect of the surface potential on the transport properties was estimated using the Boltzmann equation with a constant relaxation time. The results reveal that the surface potential dramatically alters the density of states of T-point holes, whereas it has very little effect on the density of states of L-point holes. This is because the wavefunctions at the L- and T-points have different symmetries. The electrical conductivity increases and the Seebeck coefficient decreases with increasing surface potential. The maximum absolute value of the Seebeck coefficient decreases drastically with increasing surface potential. The Seebeck coefficient has a much stronger dependence on the surface potential than on the wire diameter. These results demonstrate that the transport properties of Bi nanowires are very sensitive to the surface potential.