Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations

IF 4.8 Q2 NANOSCIENCE & NANOTECHNOLOGY
Manoel Alves Machado Filho, Ching-Lien Hsiao, Renato Batista dos Santos, Lars Hultman, Jens Birch and Gueorgui K. Gueorguiev*, 
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引用次数: 14

Abstract

By addressing precursor prevalence and energetics using the DFT-based synthetic growth concept (SGC), the formation mechanism of self-induced InAlN core–shell nanorods (NRs) synthesized by reactive magnetron sputter epitaxy (MSE) is explored. The characteristics of In- and Al-containing precursor species are evaluated considering the thermal conditions at a typical NR growth temperature of around 700 °C. The cohesive and dissociation energies of In-containing precursors are consistently lower than those of their Al-containing counterparts, indicating that In-containing precursors are more weakly bonded and more prone to dissociation. Therefore, In-containing species are expected to exhibit lower abundance in the NR growth environment. At increased growth temperatures, the depletion of In-based precursors is even more pronounced. A distinctive imbalance in the incorporation of Al- and In-containing precursor species (namely, AlN/AlN+, AlN2/AlN2+, Al2N2/Al2N2+, and Al2/Al2+ vs InN/InN+, InN2/InN2+, In2N2/In2N2+, and In2/In2+) is found at the growing edge of the NR side surfaces, which correlates well with the experimentally obtained core–shell structure as well as with the distinctive In-rich core and vice versa for the Al-rich shell. The performed modeling indicates that the formation of the core–shell structure is substantially driven by the precursors’ abundance and their preferential bonding onto the growing edge of the nanoclusters/islands initiated by phase separation from the beginning of the NR growth. The cohesive energies and the band gaps of the NRs show decreasing trends with an increment in the In concentration of the NRs’ core and with an increment in the overall thickness (diameter) of the NRs. These results reveal the energy and electronic reasons behind the limited growth (up to ∼25% of In atoms of all metal atoms, i.e., InxAl1–xN, x ∼ 0.25) in the NR core and may be qualitatively perceived as a limiting factor for the thickness of the grown NRs (typically <50 nm).

Abstract Image

自诱导核壳纳米棒:由从头算模拟揭示的形成和稳定性
通过使用基于DFT的合成生长概念(SGC)解决前驱体的普遍性和能量学问题,探索了通过反应磁控溅射外延(MSE)合成的自诱导InAlN核壳纳米棒(NRs)的形成机制。考虑到在700°C左右的典型NR生长温度下的热条件,评估了含In和Al前体物种的特性。含In的前体的内聚能和离解能始终低于含Al的前体,这表明含In的前驱体结合更弱,更容易离解。因此,含In物种在NR生长环境中表现出较低的丰度。在生长温度升高的情况下,铟基前体的损耗更加明显。在NR侧表面的生长边缘处发现含Al和in的前体物种(即AlN/AlN+、AlN2/AlN2+、Al2N2/Al2N2+和Al2/Al2+与InN/InN+、InN2/InN2+、In2N2/In2N2+和In2/In2+)的掺入的明显不平衡,这与实验获得的核-壳结构以及独特的富In核密切相关,反之亦然。所进行的建模表明,核壳结构的形成基本上是由前体的丰度及其在纳米团簇/岛的生长边缘上的优先键合驱动的,这是由NR生长开始的相分离引发的。NRs的内聚能和带隙随着NRs核心in浓度的增加和NRs总厚度(直径)的增加而呈下降趋势。这些结果揭示了NR核中有限生长(所有金属原子的In原子高达~25%,即InxAl1–xN,x~0.25)背后的能量和电子原因,并且可以定性地视为生长的NR厚度的限制因素(通常<;50 nm)。
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来源期刊
ACS Nanoscience Au
ACS Nanoscience Au 材料科学、纳米科学-
CiteScore
4.20
自引率
0.00%
发文量
0
期刊介绍: ACS Nanoscience Au is an open access journal that publishes original fundamental and applied research on nanoscience and nanotechnology research at the interfaces of chemistry biology medicine materials science physics and engineering.The journal publishes short letters comprehensive articles reviews and perspectives on all aspects of nanoscience and nanotechnology:synthesis assembly characterization theory modeling and simulation of nanostructures nanomaterials and nanoscale devicesdesign fabrication and applications of organic inorganic polymer hybrid and biological nanostructuresexperimental and theoretical studies of nanoscale chemical physical and biological phenomenamethods and tools for nanoscience and nanotechnologyself- and directed-assemblyzero- one- and two-dimensional materialsnanostructures and nano-engineered devices with advanced performancenanobiotechnologynanomedicine and nanotoxicologyACS Nanoscience Au also publishes original experimental and theoretical research of an applied nature that integrates knowledge in the areas of materials engineering physics bioscience and chemistry into important applications of nanomaterials.
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