Relation between nanomorphology and energy bands of Si nanowires

We report total-energy electronic-structure calculations performed for Si nanowires along the [100] and [110] directions within the local density approximation in the density-functional theory. Energy-band structures of Si nanowires with a cross-sectional dimension in the range of 1 to 6 nm are clarified for a variety of cross-sectional morphologies. Sidewall roughness inevitably existing in real experimental situations is examined and its effects on the electron states are revealed. We find that the nanometer scale morphology of the cross-sections of the nanowires interestingly affects the energy-band structures. The implication of the obtained electronic structures is discussed in case that Si nanowires are utilized in the next-generation field-effect transistors.