Walter Schottky Institut and Physics Department, Technische Universität München , Am Coulombwall 4, 85748 Garching, Germany.
Nano Lett. 2015 Mar 11;15(3):1773-9. doi: 10.1021/nl504446r. Epub 2015 Feb 3.
In this work the position-controlled growth of GaN nanowires (NWs) on diamond by means of molecular beam epitaxy is investigated. In terms of growth, diamond can be seen as a model substrate, providing information of systematic relevance also for other substrates. Thin Ti masks are structured by electron beam lithography which allows the fabrication of perfectly homogeneous GaN NW arrays with different diameters and distances. While the wurtzite NWs are found to be Ga-polar, N-polar nucleation leads to the formation of tripod structures with a zinc-blende core which can be efficiently suppressed above a substrate temperature of 870 °C. A variation of the III/V flux ratio reveals that both axial and radial growth rates are N-limited despite the globally N-rich growth conditions, which is explained by the different diffusion behavior of Ga and N atoms. Furthermore, it is shown that the hole arrangement has no effect on the selectivity but can be used to force a transition from nanowire to nanotube growth by employing a highly competitive growth regime.
本文研究了通过分子束外延在金刚石上进行位置受控的 GaN 纳米线（NWs）生长。从生长的角度来看，金刚石可以被视为一种模型衬底，为其他衬底提供具有系统相关性的信息。通过电子束光刻对薄 Ti 掩模进行构图，可制造出具有不同直径和间距的完全均匀 GaN NW 阵列。发现 wurtzite NW 是 Ga 极性的，而 N 极性成核导致形成具有闪锌矿芯的三脚架结构，当衬底温度高于 870°C 时，这种结构可以被有效抑制。III/V 通量比的变化表明，尽管生长条件整体上是富 N 的，但轴向和径向生长速率均受 N 限制，这可以通过 Ga 和 N 原子的不同扩散行为来解释。此外，还表明空穴排列对选择性没有影响，但可以通过采用竞争激烈的生长模式来迫使从纳米线到纳米管的生长转变。
