Ruhstorfer Daniel, Lang Armin, Matich Sonja, Döblinger Markus, Riedl Hubert, Finley Jonathan J, Koblmüller Gregor
Walter Schottky Institute and Physics Department, Technical University of Munich, Garching, Germany.
Department of Chemistry, Ludwig-Maximilians-University Munich, Munich, Germany.
Nanotechnology. 2021 Mar 26;32(13):135604. doi: 10.1088/1361-6528/abcdca.
We report a comprehensive study of the growth dynamics in highly periodic, composition tunable InAsSb nanowire (NW) arrays using catalyst-free selective area molecular beam epitaxy. Employing periodically patterned SiO-masks on Si (111) with various mask opening sizes (20-150 nm) and pitches (0.25-2 μm), high NW yield of >90% (irrespective of the InAsSb alloy composition) is realized by the creation of an As-terminated 1 × 1-Si(111) surface prior to NW nucleation. While the NW aspect ratio decreases continually with increasing Sb content (x from 0% to 30%), we find a remarkable dependence of the aspect ratio on the mask opening size yielding up to ∼8-fold increase for openings decreasing from 150 to 20 nm. The effects of the interwire separation (pitch) on the NW aspect ratio are strongest for pure InAs NWs and gradually vanish for increasing Sb content, suggesting that growth of InAsSb NW arrays is governed by an In surface diffusion limited regime even for the smallest investigated pitches. Compositional analysis using high-resolution x-ray diffraction reveals a substantial impact of the pitch on the alloy composition in homogeneous InAsSb NW arrays, leading to much larger x as the pitch increases due to decreasing competition for Sb adatoms. Scanning transmission electron microscopy and associated energy-dispersive x-ray spectroscopy performed on the cross-sections of individual NWs reveal an interesting growth-axis dependent core-shell like structure with a discontinuous few-nm thick Sb-deficient coaxial boundary layer and six Sb-deficient corner bands. Further analysis evidences the presence of a nanoscale facet at the truncation of the (111)B growth front and {1-10} sidewall surfaces that is found responsible for the formation of the characteristic core-shell structure.
我们报告了一项关于使用无催化剂选择性区域分子束外延技术生长高度周期性、成分可调的InAsSb纳米线（NW）阵列的生长动力学的综合研究。在具有各种掩膜开口尺寸（20 - 150 nm）和间距（0.25 - 2 μm）的Si（111）上采用周期性图案化的SiO掩膜，通过在NW成核之前创建As终止的1×1 - Si（111）表面，实现了>90%的高NW产率（与InAsSb合金成分无关）。虽然NW的纵横比随着Sb含量（x从0%增加到30%）的增加而持续降低，但我们发现纵横比对掩膜开口尺寸有显著依赖性，对于开口尺寸从150 nm减小到20 nm的情况，纵横比可增加约8倍。线间距对NW纵横比的影响对于纯InAs NW最强，并且随着Sb含量的增加逐渐消失，这表明即使对于研究的最小间距，InAsSb NW阵列的生长也受In表面扩散限制机制支配。使用高分辨率x射线衍射进行的成分分析表明，间距对均匀InAsSb NW阵列中的合金成分有重大影响，由于对Sb吸附原子的竞争减少，随着间距增加x会大得多。对单个NW的横截面进行的扫描透射电子显微镜和相关的能量色散x射线光谱分析揭示了一种有趣的与生长轴相关的核壳状结构，具有不连续的几纳米厚的Sb缺陷同轴边界层和六个Sb缺陷角带。进一步分析证明在（111）B生长前沿和{1 - 10}侧壁表面的截断处存在一个纳米级小面，该小面被认为是形成特征核壳结构的原因。
