Strain induced band dispersion engineering in Si nanosheets

The electronic properties of strained hydrogen-passivated Si nanosheets are investigated using the first-principles density functional theory. Asymmetrical strain has been found to cause a direct-to-indirect transition in the (100) Si nanosheet, while symmetrical strain retains its direct band gap characteristic. Under asymmetrical strain along the 〈100〉 direction, the direct band gap of the (110) Si nanosheet exhibits unique characteristics, with the direct band gap varying linearly with strain. Similar band gap variation behaviors are observed for the (110) Si nanosheet subject to symmetrical and asymmetrical strains along the 〈110〉 direction. The various strain dependences are attributed to the changes in its charge density. Our results can be used to guide the strain engineering of the electronic properties of low-dimensional silicon materials. © 2011 American Chemical Society.