Tunable electronic band structures of hydrogen-terminated 〈112〉 silicon nanowires

The possibility of inducing indirect-to-direct band gap transition in silicon nanowires (SiNWs) by changing wire diameter is well known. Here, we show that for 〈112〉-oriented SiNWs indirect-to-direct band gap transition can be tuned simply by changing the wire cross-section shape or the cross-sectional aspect ratio of the (111) and (110) facets that enclose the wire, instead of changing the wire diameter. The cross-sectional aspect ratio must be smaller than 0.5 in order to maintain a direct band gap, indicating the important role of the (110) facet. © 2008 American Institute of Physics.