Si-Ge核壳纳米线禁带宽度的形貌效应

Shape-dependent Band Gap of Si-Ge Core-shell Nanowire

基于连续介质力学和键弛豫理论等方法,从原子键长和键强的变化以及应变的角度出发研究了包括三边形、四边形、六边形和圆形等不同形貌Si纳米线的能隙。研究结果表明,表面原子,特别是顶角和棱边上的原子,对多边形纳米线能带结构会产生重大影响。此外,研究发现纳米线的能隙随尺寸的减少而增大,并且Ge外延层厚度的改变也可实现对能带的调控。结果与实验测量吻合较好,这也说明该理论方法的可行,可为今后分析多边形核壳纳米结构的能隙以及为Si基材料的应用提供借鉴。

Shape-dependent band gap of Si nanowire(NW)with polygonal cross-sectional shapes,including trigon,tetragon,hexagon,and circle,from the change of the bond length,stronger,as well as strain is explored based on the continuum mechanics and atomic-bond-relaxation approach.It is found that the surface atoms,especially the atoms at the top and edge,play a significant role on the band structure of NWs.Moreover,the band gap of NWs is not only modified by the dimension,but also modulated by the epitaxial layer of Ge.Our predictions are consistent with the available evidences,suggesting that this model provides an effective method for analyzing the band gap and developing Si-based nanostructures for the desirable applications in NWs.