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).
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.