Kindlund Hanna, Zamani Reza R, Persson Axel R, Lehmann Sebastian, Wallenberg L Reine, Dick Kimberly A
Division of Solid State Physics , Lund University , Box 118 , S-221 00 Lund , Sweden.
Centre for Analysis and Synthesis , Lund University , Box 124 , S-221 00 Lund , Sweden.
Nano Lett. 2018 Sep 12;18(9):5775-5781. doi: 10.1021/acs.nanolett.8b02421. Epub 2018 Aug 28.
Using AlSb as the model system, we demonstrate that kinetic limitations can lead to the preferential growth of wurtzite (WZ) AlSb shells rather than the thermodynamically stable zinc-blende (ZB) AlSb and that the WZ and ZB relative thickness can be tuned by a careful control of the deposition parameters. We report selective heteroepitaxial radial growth of AlSb deposited by metal-organic vapor phase epitaxy (MOVPE) on InAs nanowire core templates with engineered lengths of axial WZ and ZB segments. AlSb shell thickness, crystal phase, nanostructure, and composition are investigated as a function of the shell growth temperature, T, using scanning electron microscopy, transmission electron microscopy, electron tomography, and energy-dispersive X-ray spectroscopy. We find that ZB- and WZ-structured AlSb shells grow heteroepitaxially around the ZB and WZ segments of the InAs core, respectively. Surprisingly, at 390 < T < 450 °C, the WZ-AlSb shells are thicker than the ZB-AlSb shells, and their thickness increases with decreasing T. In comparison, the ZB-AlSb shell thicknesses increase slightly with increasing T. We find that the increased thickness of the WZ-AlSb shells is due to the formation and enhanced deposition on {112̅0} facets rather than on the more commonly grown {101̅0} sidewall facets. Overall, these results, which are in direct contrast with previous reports suggesting that heteroepitaxial radial growth of III-antimonides is always favored on the ZB-structure facets, indicate that the growth of WZ-AlSb is preferred over the thermodynamically stable ZB-AlSb at lower growth temperatures. We attribute this behavior to kinetic limitations of MOVPE of AlSb on ZB and WZ phases of InAs.
以AlSb作为模型体系，我们证明了动力学限制会导致纤锌矿（WZ）结构的AlSb壳层优先生长，而非热力学稳定的闪锌矿（ZB）结构的AlSb，并且通过仔细控制沉积参数可以调节WZ和ZB的相对厚度。我们报道了通过金属有机气相外延（MOVPE）在具有轴向WZ和ZB段工程长度的InAs纳米线芯模板上选择性异质外延径向生长AlSb。使用扫描电子显微镜、透射电子显微镜、电子断层扫描和能量色散X射线光谱，研究了AlSb壳层厚度、晶相、纳米结构和组成与壳层生长温度T的关系。我们发现，ZB结构和WZ结构的AlSb壳层分别在InAs芯的ZB段和WZ段周围异质外延生长。令人惊讶的是，在390 < T < 450 °C时，WZ-AlSb壳层比ZB-AlSb壳层更厚，并且其厚度随T的降低而增加。相比之下，ZB-AlSb壳层厚度随T的增加略有增加。我们发现WZ-AlSb壳层厚度增加是由于在{112̅0}面上形成并增强了沉积，而不是在更常见生长的{101̅0}侧壁面上。总体而言，这些结果与之前的报道直接相反，之前的报道表明III - 锑化物的异质外延径向生长总是在ZB结构面上更有利，这表明在较低生长温度下，WZ-AlSb的生长优于热力学稳定的ZB-AlSb。我们将这种行为归因于AlSb在InAs的ZB和WZ相上MOVPE的动力学限制。
