Crystalline, Phononic, and Electronic Properties of Heterostructured Polytypic Ge Nanowires by Raman Spectroscopy
Crystalline, Phononic, and Electronic Properties of Heterostructured Polytypic Ge Nanowires by Raman Spectroscopy
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DOI：
10.1021/acs.nanolett.8b03073
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发表时间：
2018-11-01
期刊：
影响因子：
10.8
通讯作者：
Zardo, Ilaria
中科院分区：
文献类型：
--
作者：
Fasolato, Claudia;De Luca, Marta;Zardo, Ilaria
半导体纳米线（NW）提供了在纳米结构中承载不同晶相的前所未有的机会，这使得能够在材料组成不变的情况下形成多型异质结构。这一特性增强了多型异质结构纳米线在光电和声子应用中的潜力。在这项工作中，我们调查立方锗纳米线小（类似于20纳米）六边形域形成由于应变诱导相变。通过结合非破坏性的光学技术（拉曼光谱）与密度泛函理论（DFT）计算，我们评估的声子性能的六方锗，确定晶体的相位变化沿着NW轴，并相当显着，重建的两个多型体的相对取向。此外，我们还提供了有关布里渊区中与六角Ge中发生直接带隙复合的布里渊区（F）不同的点处异质结构的电子能带排列的信息。我们展示了拉曼光谱的多功能性，并表明它可以用来确定最具挑战性的异质结构（一个多型，纳米级异质结构与恒定的材料组成）的主要晶体，声子和电子特性。我们建立的一般程序可以应用于几种类型的异质结构。
Semiconducting nanowires (NWs) offer the unprecedented opportunity to host different crystal phases in a nanostructure, which enables the formation of polytypic heterostructures where the material composition is unchanged. This characteristic boosts the potential of polytypic heterostructured NWs for optoelectronic and phononic applications. In this work, we investigate cubic Ge NWs where small (similar to 20 nm) hexagonal domains are formed due to a strain-induced phase transformation. By combining a nondestructive optical technique (Raman spectroscopy) with density-functional theory (DFT) calculations, we assess the phonon properties of hexagonal Ge, determine the crystal phase variations along the NW axis, and, quite remarkably, reconstruct the relative orientation of the two polytypes. Moreover, we provide information on the electronic band alignment of the heterostructure at points of the Brillouin zone different from the one (F) where the direct band gap recombination in hexagonal Ge takes place. We demonstrate the versatility of Raman spectroscopy and show that it can be used to determine the main crystalline, phononic, and electronic properties of the most challenging type of heterostructure (a polytypic, nanoscale heterostructure with constant material composition). The general procedure that we establish can be applied to several types of heterostructures.