Role of surfaces and interfaces in mechanical and piezoresistive properties of bare Si/Ge heterostructure nanowires

•Si3 − x/Gex HNWs with clear interfaces have semiconductor-like band, while those with mixed interfaces have metal-like band.•Enhanced piezoresistive effects can be obtained for HNWs with clear interfaces, as compared with those with mixed interfaces.

Mechanical and piezoresistive properties of bare Si3 − x/Gex heterostructure nanowires (HNWs) have been investigated by using first-principles calculations. It is found that Young's modulus of Si2/Ge1 HNW is much smaller than that of other Si3 − x/Gex, attributed to the partial surface reconstruction. Moreover, Si3 − x/Gex HNWs with clear interfaces exhibit semiconductor-like band, while those with mixed interfaces are of metal-like band. Enhanced piezoresistive coefficients can be obtained for HNWs with clear interfaces, as compared with those with mixed interfaces. Our results indicate that bare Si3 − x/Gex HNWs with clear interfaces have potential applications as pressure sensors due to the enhanced piezoresistance.