First-Principle Study of Energy-Band Control by Cross-Sectional Morphology in [110]-Si Nanowires

Si nanowire field-effect transistors (SiNW FETs) are expected to be boosters in postscaling semiconductor technology. Hydrogenated SiNWs that are formed by treatments of pristine or oxidized SiNWs with hydrogen fluorides offer a stage where salient properties of SiNWs are investigated. Electronic structures of such hydrogenated SiNWs have been indeed studied by density functional theory (DFT), although the NWs considered so far are much thinner than those experimentally synthesized. Calculations have been performed in the local density approximation (LDA) in DFT. Normconserving pseudopotentials generated by using the Troullier–Martins scheme are adopted to describe the electron–ion interaction. In the experiment, however, SiNWs have a subnanometer roughness by the oxidation or etching in fabrication processes, and it is difficult to eliminate roughness in the sidewall of SiNWs in their fabrication processes. Therefore, it is important to clarify the effects of sidewall roughness. These effects can be regarded as the effects of the cross-sectional morphology.