Schmiedeke Paul, Panciera Federico, Harmand Jean-Christophe, Travers Laurent, Koblmüller Gregor
Technical University of Munich, Walter Schottky Institute, TUM School of Natural Sciences, Physics Department Garching 85747 Germany
Centre for Nanoscience and Nanotechnology, CNRS, Université Paris-Saclay 10 Boulevard Thomas Gobert 91120 Palaiseau France.
Nanoscale Adv. 2023 May 5;5(11):2994-3004. doi: 10.1039/d3na00135k. eCollection 2023 May 30.
Nanowires (NWs) offer unique opportunities for tuning the properties of III-V semiconductors by simultaneously controlling their nanoscale dimensions and switching their crystal phase between zinc-blende (ZB) and wurtzite (WZ). While much of this control has been enabled by direct, forward growth, the reverse reaction, , crystal decomposition, provides very powerful means to further tailor properties towards the ultra-scaled dimensional level. Here, we use transmission electron microscopy (TEM) to investigate the thermal decomposition kinetics of clean, ultrathin GaAs NWs and the role of distinctly different crystal polytypes in real-time and on the atomic scale. The whole process, from the NW growth to the decomposition, is conducted without breaking vacuum to maintain pristine crystal surfaces. Radial decomposition occurs much faster for ZB- compared to WZ-phase NWs, due to the development of nano-faceted sidewall morphology and sublimation along the entire NW length. In contrast, WZ NWs form single-faceted, vertical sidewalls with decomposition proceeding only step-flow mechanism from the NW tip. Concurrent axial decomposition is generally faster than the radial process, but is significantly faster (∼4-fold) in WZ phase, due to the absence of well-defined facets at the tip of WZ NWs. The results further show quantitatively the influence of the NW diameter on the sublimation and step-flow decomposition velocities elucidating several effects that can be exploited to fine-tune the NW dimensions.
纳米线（NWs）为调控III-V族半导体的性质提供了独特的机会，可通过同时控制其纳米尺度尺寸并在闪锌矿（ZB）和纤锌矿（WZ）之间切换其晶体相来实现。虽然这种控制大多是通过直接的正向生长实现的，但逆反应，即晶体分解，为在超小尺度维度水平上进一步定制性质提供了非常强大的手段。在此，我们使用透射电子显微镜（TEM）来研究清洁的超薄砷化镓纳米线的热分解动力学以及不同晶体多型体在实时和原子尺度上的作用。从纳米线生长到分解的整个过程在不破坏真空的情况下进行，以保持原始晶体表面。与WZ相纳米线相比，ZB相纳米线的径向分解速度要快得多，这是由于纳米刻面侧壁形态的发展以及沿整个纳米线长度的升华。相比之下，WZ纳米线形成单面的垂直侧壁，分解仅从纳米线尖端以台阶流机制进行。同时发生的轴向分解通常比径向过程快，但在WZ相中要快得多（约4倍），这是由于WZ纳米线尖端没有明确的刻面。结果还定量地显示了纳米线直径对升华和台阶流分解速度的影响，阐明了几种可用于微调纳米线尺寸的效应。
