TEM EDS analysis of epitaxially-grown self-assembled indium islands

Jasmine Sears (1) , Ricky Gibson (1) , Michael Gehl (1) , Sander Zandbergen (1) , Patrick Keiffer (1) , Nima Nader (1) , Joshua Hendrickson (2) , Alexandre Arnoult (3) , Galina Khitrova (4)

1 University of Arizona
2 AFRL - Air Force Research Laboratory
3 LAAS-TEAM - Service Techniques et Équipements Appliqués à la Microélectronique
4 OSC - Optical Sciences Center

Epitaxially-grown self-assembled indium nanostructures, or islands, show promise as nanoantennas. The elemental composition and internal structure of indium islands grown on gallium arsenide are explored using Transmission Electron Microscopy (TEM) Energy Dispersive Spectroscopy (EDS). Several sizes of islands are examined, with larger islands exhibiting high (>94%) average indium purity and smaller islands containing inhomogeneous gallium and arsenic contamination. These results enable more accurate predictions of indium nanoantenna behavior as a function of growth parameters. 1. Background As the field of plasmonic nanostructures develops, there is increasing demand for epitaxially-grown metallic nanostructures. Metal-on-semiconductor nanoantennas, which operate at optical and near-infrared wavelengths, have a wide range of potential applications, from low-cost photodetectors1 to higher-efficiency solar cells.2 Currently, nanoantenna fabrication is often performed separately from substrate preparation;3-8 this discontinuity can adversely affect the finished product through contamination and impurities introduced during fabrication. One method for avoiding these issues is to epitaxially grow both the substrate and plasmonic nanostructure, with the structure self-assembling from a uniformly-deposited metal layer such as silver or indium.9,10 Self-assembled nanostructures can additionally benefit from a better contact interface between structure and substrate compared to other fabrication methods. Epitaxially-grown nanostructures may also have applications in quantum computing.11,12 Majorana fermions, a candidate for qubit construction, have been observed in InSb nanowires coupled to superconducting NbTiN.13 Other s-wave superconductor-1D semiconductor systems are also expected to generate Majorana fermions; InAs and indium have been identified as a potential semiconductor and superconductor, respectively.14,15 InAs nanowires can be grown epitaxially, suggesting that self-assembled indium islands may allow for the epitaxial growth of entire Majorana fermion-generating heterostructures. While epitaxially-grown self-assembled indium islands show promise as nanoantennas,16 the internal structure of these islands has not been thoroughly explored. Prior work has indicated that these structures may contain impurities unique to the epitaxial growth process.17 This paper seeks to describe and analyze the internal structure of indium islands grown under three different sets of growth conditions, in order to better predict the behavior and future applications of these plasmonic nanostructures. 2. Experiment

Domaines: Matière Condensée [cond-mat]

Jasmine Sears, Ricky Gibson, Michael Gehl, Sander Zandbergen, Patrick Keiffer, et al.. TEM EDS analysis of epitaxially-grown self-assembled indium islands. AIP Advances, 2017, 7 (5), ⟨10.1063/1.4983492⟩. ⟨hal-01912407⟩