Improving pseudo-van der Waals epitaxy of self-assembled InAs nanowires on graphene via MOCVD parameter space mapping
Improving pseudo-van der Waals epitaxy of self-assembled InAs nanowires on graphene via MOCVD parameter space mapping
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DOI：
10.1039/c8ce01666f
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发表时间：
2019-01-28
期刊：
影响因子：
3.1
通讯作者：
Mohseni, Parsian K.
中科院分区：
文献类型：
--
作者：
Baboli, Mohadeseh A.;Slocum, Michael A.;Mohseni, Parsian K.
惰性二维单层材料上的 III-V 纳米结构的异质自组装使得新型混合纳米系统具有独特的性能，可用于低成本、低重量的柔性光电和纳米电子器件应用。在这里，研究了通过金属有机化学气相沉积 (MOCVD) 将 InAs 纳米线 (NW) 与单层石墨烯 (SLG) 连续膜异质集成的伪范德华外延 (vdWE) 生长参数空间。纳米线的长度、直径和数量密度以及寄生岛的面积覆盖率被量化为关键生长变量的函数，包括生长温度、V/III 比率以及金属有机和氢化物前驱体的总流速。在选定的一组最佳生长条件下，实现了包含高数密度阵列的高纵横比纳米线的自组装和同时最小化寄生生长覆盖范围之间的折衷。对各种生长条件下形成的 NW 晶体结构的探索表明，特征多型和无序晶格在探索的参数空间内是不变的。生长演化研究表明，在最佳生长条件的探索时间范围内，轴向和径向生长速率逐渐降低，这归因于供应有限的竞争性生长机制。引入了两种策略来进一步优化增长。首先，结果表明，缺乏预生长原位胂表面处理会导致寄生岛覆盖率降低约 0.62，而 NW 纵横比和数量密度同时提高。其次，使用两步流量调制生长程序可以实现高深宽比 InAs 纳米线的密集场。通过应用研究和生长参数空间的优化，石墨表面高深宽比（>80）InAs纳米线阵列的vdWE实现了最高报道的840 nm min(-1)轴向生长速率和类似于8.3 x 10(8) cm(-2)的纳米线数密度。这项工作旨在为自组装III-V半导体纳米线（例如功能性二维单层材料上的In基三元和四元合金）的vdWE提供指导，以实现柔性光电子和串联结光伏器件的应用。
Heterogeneous self-assembly of III-V nanostructures on inert two-dimensional monolayer materials enables novel hybrid nanosystems with unique properties that can be exploited for low-cost and low-weight flexible optoelectronic and nanoelectronic device applications. Here, the pseudo-van der Waals epitaxy (vdWE) growth parameter space for heterogeneous integration of InAs nanowires (NWs) with continuous films of single layer graphene (SLG) via metalorganic chemical vapor deposition (MOCVD) is investigated. The length, diameter, and number density of NWs, as well as areal coverage of parasitic islands, are quantified as functions of key growth variables including growth temperature, V/III ratio, and total flow rate of metalorganic and hydride precursors. A compromise between self-assembly of high aspect ratio NWs comprising high number density arrays and simultaneous minimization of parasitic growth coverage is reached under a selected set of optimal growth conditions. Exploration of NW crystal structures formed under various growth conditions reveals that a characteristic polytypic and disordered lattice is invariant within the explored parameter space. A growth evolution study reveals a gradual reduction in both axial and radial growth rates within the explored timeframe for the optimal growth conditions, which is attributed to a supply-limited competitive growth regime. Two strategies are introduced for further growth optimization. Firstly, it is shown that the absence of a pre-growth in situ arsine surface treatment results in a reduction of parasitic island coverage by factor of similar to 0.62, while NW aspect ratio and number densities are simultaneously enhanced. Secondly, the use of a two-step flow-modulated growth procedure allows for realization of dense fields of high aspect ratio InAs NWs. As a result of the applied studies and optimization of the growth parameter space, the highest reported axial growth rate of 840 nm min(-1) and NW number density of similar to 8.3 x 10(8) cm(-2) for vdWE of high aspect ratio (>80) InAs NW arrays on graphitic surfaces are achieved. This work is intended to serve as a guide for vdWE of self-assembled III-V semiconductor NWs such as In-based ternary and quaternary alloys on functional two-dimensional monolayer materials, toward device applications in flexible optoelectronics and tandem-junction photovoltaics.