InAs-AlInAs和InAs-AlInP核壳纳米线的结构研究
Structural Investigation of InAs-AlInAs and InAs-AlInP Core-Shell Nanowires
摘要：
在气体源分子束外延（GS-MBE）系统中，采用金辅助气液固（VLS）方法在GaAs衬底上生长了InAs纳米线。钝化的InAs纳米线使用InP壳证明是困难的，由于形成轴向而不是核-壳结构的趋势。为了避免这个问题，通过在InAs纳米线的侧壁上直接气相-固相沉积来生长具有标称Al组成分数x = 0.20、0.36或0.53的Al $_x$ In $_{1-x}$ As或Al $_x$ In $_{1-x}$ P壳。通过透射电子显微镜表征发现，在壳中添加Al导致从VLS到沿纳米线长度具有均匀壳厚度的气-固生长模式的显著转变。这种转变的可能机制包括减少吸附原子扩散，金种子颗粒的相变和表面活性剂的影响。InAs-AlInP核壳纳米线表现出失配位错，而具有较低应变的InAs-AlInAs纳米线似乎没有缺陷。
英文摘要：
InAs nanowires were grown on GaAs substrates by the Au-assisted vapour-liquid-solid (VLS) method in a gas source molecular beam epitaxy (GS-MBE) system. Passivation of the InAs nanowires using InP shells proved difficult due to the tendency for the formation of axial rather than core-shell structures. To circumvent this issue, Al$_x$In$_{1-x}$As or Al$_x$In$_{1-x}$P shells with nominal Al composition fraction of x = 0.20, 0.36, or 0.53 were grown by direct vapour-solid deposition on the sidewalls of the InAs nanowires. Characterization by transmission electron microscopy revealed that the addition of Al in the shell resulted in a remarkable transition from the VLS to the vapour-solid growth mode with uniform shell thickness along the nanowire length. Possible mechanisms for this transition include reduced adatom diffusion, a phase change of the Au seed particle and surfactant effects. The InAs-AlInP core-shell nanowires exhibited misfit dislocations, while the InAs-AlInAs nanowires with lower strain appeared to be free of defects.
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