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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Electronic Structure and Epitaxy of CdTe Shells on InSb Nanowires

Abstract Indium antimonide (InSb) nanowires are used as building blocks for quantum devices because of their unique properties, that is, strong spin‐orbit interaction and large Landé g‐factor. Integrating InSb nanowires with other materials could potentially unfold novel devices with distinctive functionality. A prominent example is the combination of InSb nanowires with superconductors for the emerging topological particles research. Here, the combination of the II–VI cadmium telluride (CdTe) with the III–V InSb in the form of core–shell (InSb–CdTe) nanowires is investigated and potential applications based on the electronic structure of the InSb–CdTe interface and the epitaxy of CdTe on the InSb nanowires are explored. The electronic structure of the InSb–CdTe interface using density functional theory is determined and a type‐I band alignment is extracted with a small conduction band offset ( ⩽0.3 eV). These results indicate the potential application of these shells for surface passivation or as tunnel barriers in combination with superconductors. In terms of structural quality, it is demonstrated that the lattice‐matched CdTe can be grown epitaxially on the InSb nanowires without interfacial strain or defects. These shells do not introduce disorder to the InSb nanowires as indicated by the comparable field‐effect mobility measured for both uncapped and CdTe‐capped nanowires.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Few-mode and anisotropic quantum transport in InSb nanoribbons using an all-van der Waals material-based gate

High-quality electrostatic gating is a fundamental ingredient for successful semiconducting device physics, and a key element of realizing clean quantum transport. Inspired by the widespread improvement of transport quality when two-dimensional van der Waals (vdW) materials are gated exclusively by other vdW materials, we have developed a method for gating non-vdW materials with an all-vdW gate stack, consisting of a hexagonal boron nitride dielectric layer and a few-layer graphite gate electrode. We demonstrate this gating approach on MOVPE-grown InSb nanoribbons (NRs), a novel variant of the InSb nanowire, with a flattened cross-section. In our all-vdW gated NR devices we observe conductance features that are reproducible and have low- to near-zero gate hysteresis. We also report quantized conductance, which persists to lower magnetic fields and longer channel lengths than typical InSb nanowire devices reported to date. Additionally, we observe level splitting that is highly anisotropic in an applied magnetic field, which we attribute to the ribbon cross-section. The performance of our devices is consistent with the reduced disorder expected from the all-vdW gating scheme, and marks the first report of ballistic, few-modes quantum transport in a non-vdW material with an all-vdW gate. Our results establish all-vdW gating as a promising approach for high-quality gating of non-vdW materials for quantum transport, which is in principle applicable generically, beyond InSb systems. In addition, the work showcases the specific potential of all-vdW gate/InSb NR devices for enabling clean quantum devices that may be relevant for spintronics and topological superconductivity studies.

InSb↗
DOE OSTI2022

Electronic Structure of InAs and InSb Surfaces: Density Functional Theory and Angle-Resolved Photoemission Spectroscopy

The electronic structure of surfaces plays a key role in the properties of quantum devices. However, surfaces are also the most challenging to simulate and engineer. Here, in this work, the electronic structure of InAs(001), InAs(111), and InSb(110) surfaces is studied using a combination of density functional theory (DFT) and angle-resolved photoemission spectroscopy (ARPES). Large-scale first principles simulations are enabled by using DFT calculations with a machine-learned Hubbard U correction [npj Comput. Mater. 6, 180 (2020)]. To facilitate direct comparison with ARPES results, a “bulk unfolding” scheme is implemented by projecting the calculated band structure of a supercell surface slab model onto the bulk primitive cell. For all three surfaces, a good agreement is found between DFT calculations and ARPES. For InAs(001), the simulations clarify the effect of the surface reconstruction. Different reconstructions are found to produce distinctive surface states, which may be detected by ARPES with low photon energies. For InAs(111) and InSb(110), the simulations help elucidate the effect of oxidation. Owing to larger charge transfer from As to O than from Sb to O, oxidation of InAs(111) leads to significant band bending and produces an electron pocket, whereas oxidation of InSb(110) does not. The combined theoretical and experimental results may inform the design of quantum devices based on InAs and InSb semiconductors, for example, topological qubits utilizing the Majorana zero modes.

42 ENGINEERING↗
DOE OSTI2021

Near-field photonic thermal diode based on hBN and InSb films

A thermal diode is a two-terminal device that allows heat to transfer more easily in one direction (forward bias) than in the opposite direction (reverse bias). A photonic thermal diode operates in a contactless mode and may afford a large operating temperature range. Here, a near-field photonic thermal diode based on hexagonal boron nitride (hBN) and indium antimonide (InSb) films is theoretically demonstrated. In this work, the temperature dependence of the interband absorption of InSb is used to couple (or decouple) with the hyperbolic phonon polaritons in hBN. The numerical analysis predicts a rectification ratio greater than 17 for a 10 nm vacuum gap, when operating at an average temperature of 300 K and a temperature difference of 200 K. The calculated rectification ratio exceeds 35 at higher average temperatures with larger temperature differences.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Diffusive and ballistic transport in thin InSb nanowire devices using a few-layer-graphene-AlO x gate

Abstract Quantum devices based on InSb nanowires (NWs) are a prime candidate system for realizing and exploring topologically-protected quantum states and for electrically-controlled spin-based qubits. The influence of disorder on achieving reliable quantum transport regimes has been studied theoretically, highlighting the importance of optimizing both growth and nanofabrication. In this work, we consider both aspects. We developed InSb NW with thin diameters, as well as a novel gating approach, involving few-layer graphene and atomic layer deposition-grown AlO x . Low-temperature electronic transport measurements of these devices reveal conductance plateaus and Fabry–Pérot interference, evidencing phase-coherent transport in the regime of few quantum modes. The approaches developed in this work could help mitigate the role of material and fabrication-induced disorder in semiconductor-based quantum devices.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Phase field modeling of dislocations and obstacles in InSb

We present a phase-field dislocation dynamics (PFDD) model informed by first-principle calculations to elucidate the competitive dislocation nucleation and propagation between the glide and shuffle sets in InSb diamond cubic crystal. The calculations are directly informed with generalized stacking fault energy curves on the (111) slip plane for both the “glide set,” with the smaller interplanar spacing, and the “shuffle set,” with the larger interplanar spacing. The formulation also includes elastic anisotropy and the gradient term associated with the dislocation core. The PFDD calculations show that under no stress the equilibrium structure of screw glide set dislocations dissociates into Shockley partials, while those of the shuffle set dislocations do not dissociate, remaining compact. The calculated dislocation core widths of these InSb dislocations agree well with the measured values for other semiconductor materials, such as Si and GaN. We find that a shuffle set dislocation emits from a dislocation source at an applied stress about three times smaller than that needed to emit leading and trailing partials successively on the glide set plane. Once the partial dislocations in the glide set are emitted, they propagate faster than the shuffle set perfect dislocation at the same stress level.

36 MATERIALS SCIENCE↗
DOE OSTI2023

First principles study of the electronic structure of the Ni 2 MnIn / InAs and Ti 2 MnIn / InSb interfaces

We present a first principles study of the electronic and magnetic properties of epitaxial interfaces between the Heusler compounds, Ti 2 MnIn and Ni 2 MnIn, and the III-V semiconductors, InSb and InAs, respectively. We use density functional theory (DFT) with a machine-learned Hubbard U correction determined by Bayesian optimization. Here, we evaluate these interfaces for prospective applications in Majorana-based quantum computing and spintronics. In both interfaces, states from the Heusler penetrate into the gap of the semiconductor, decaying within a few atomic layers. The magnetic interactions at the interface are weak and local in space and energy. Magnetic moments of less than 0.1 µB are induced in the two atomic layers closest to the interface. The induced spin polarization around the Fermi level of the semiconductor decays within a few atomic layers. The decisive factor for the induced spin polarization around the Fermi level of the semiconductor is the spin polarization around the Fermi level in the Heusler, rather than the overall magnetic moment. As a result, the ferrimagnetic narrow-gap semiconductor Ti 2 MnIn induces a more significant spin polarization in the InSb than the ferromagnetic metal Ni 2 MnIn induces in the InAs. This is explained by the position of the transition metal d states in the Heusler with respect to the Fermi level. Based on our results, these interfaces are unlikely to be useful for Majorana devices but could be of interest for spintronics.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Growth and characterization of α-Sn thin films on In- and Sb-rich reconstructions of InSb(001)

α-Sn thin films can exhibit a variety of topologically nontrivial phases. Both studying the transitions between these phases and making use of these phases in eventual applications requires good control over the electronic and structural quality of α-Sn thin films. α-Sn growth on InSb often results in out-diffusion of indium, a p-type dopant. By growing α-Sn via molecular beam epitaxy on the Sb-rich c(4×4) surface reconstruction of InSb(001) rather than the In-rich c(8×2), we demonstrate a route to substantially decrease and minimize this indium incorporation. The reduction in indium concentration allows for the study of the surface and bulk Dirac nodes in α-Sn via angle-resolved photoelectron spectroscopy without the common approaches of bulk doping or surface dosing, simplifying topological phase identification. In this study, the lack of indium incorporation is verified in angle-resolved and angle-integrated ultraviolet photoelectron spectroscopy as well as in clear changes in the Hall response.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. In3+ is bonded in a body-centered cubic geometry to eight equivalent Sb3- atoms. All In–Sb bond lengths are 3.30 Å. Sb3- is bonded in a body-centered cubic geometry to eight equivalent In3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. In3+ is bonded to six equivalent Sb3- atoms to form a mixture of corner and edge-sharing InSb6 octahedra. The corner-sharing octahedral tilt angles are 0°. All In–Sb bond lengths are 3.07 Å. Sb3- is bonded to six equivalent In3+ atoms to form a mixture of corner and edge-sharing SbIn6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is High Pressure Cadmuum Telluride structured and crystallizes in the orthorhombic Pmm2 space group. The structure is three-dimensional. In3+ is bonded in a bent 150 degrees geometry to two equivalent Sb3- atoms. Both In–Sb bond lengths are 3.18 Å. Sb3- is bonded to two equivalent In3+ and four equivalent Sb3- atoms to form a mixture of edge and corner-sharing SbIn2Sb4 octahedra. The corner-sharing octahedra tilt angles range from 0–29°. There are two shorter (3.04 Å) and two longer (3.14 Å) Sb–Sb bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. In3+ is bonded to four equivalent Sb3- atoms to form corner-sharing InSb4 tetrahedra. All In–Sb bond lengths are 2.87 Å. Sb3- is bonded to four equivalent In3+ atoms to form corner-sharing SbIn4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to six Sb3- atoms to form InSb6 octahedra that share corners with two equivalent SbIn5Sb octahedra, corners with four equivalent InSb6 octahedra, edges with four equivalent InSb6 octahedra, and edges with eight equivalent InSb5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 0–39°. There are a spread of In–Sb bond distances ranging from 3.04–3.30 Å. In the second In3+ site, In3+ is bonded to five Sb3- atoms to form distorted InSb5 trigonal bipyramids that share corners with four equivalent SbIn5Sb octahedra, corners with five equivalent InSb5 trigonal bipyramids, edges with four equivalent InSb6 octahedra, and edges with four equivalent InSb5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 65–106°. There are a spread of In–Sb bond distances ranging from 3.05–3.22 Å. There are two inequivalent Sb3- sites. In the first Sb3- site, Sb3- is bonded to six In3+ atoms to form a mixture of edge and corner-sharing SbIn6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the second Sb3- site, Sb3- is bonded to five In3+ and one Sb3- atom to form distorted SbIn5Sb octahedra that share a cornercorner with one InSb6 octahedra, corners with five equivalent SbIn5Sb octahedra, corners with four equivalent InSb5 trigonal bipyramids, and edges with eight SbIn6 octahedra. The corner-sharing octahedra tilt angles range from 9–39°. The Sb–Sb bond length is 2.93 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is Halite, Rock Salt-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. In3+ is bonded to six equivalent Sb3- atoms to form a mixture of edge and corner-sharing InSb6 octahedra. The corner-sharing octahedra tilt angles range from 0–13°. There are a spread of In–Sb bond distances ranging from 3.06–3.09 Å. Sb3- is bonded to six equivalent In3+ atoms to form a mixture of edge and corner-sharing SbIn6 octahedra. The corner-sharing octahedra tilt angles range from 0–13°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is beta-prime cadmium gold structured and crystallizes in the orthorhombic Pmmn space group. The structure is three-dimensional. In3+ is bonded to four equivalent Sb3- atoms to form a mixture of distorted corner and edge-sharing InSb4 trigonal pyramids. There are two shorter (3.09 Å) and two longer (3.10 Å) In–Sb bond lengths. Sb3- is bonded in a 6-coordinate geometry to four equivalent In3+ and two equivalent Sb3- atoms. Both Sb–Sb bond lengths are 3.22 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb crystallizes in the monoclinic Cm space group. The structure is three-dimensional. In3+ is bonded to six equivalent Sb3- atoms to form distorted InSb6 octahedra that share corners with twelve equivalent SbIn6Sb2 hexagonal bipyramids, corners with six equivalent InSb6 octahedra, and edges with twelve equivalent InSb6 octahedra. The corner-sharing octahedra tilt angles range from 5–6°. There are a spread of In–Sb bond distances ranging from 3.08–3.42 Å. Sb3- is bonded to six equivalent In3+ and two equivalent Sb3- atoms to form distorted SbIn6Sb2 hexagonal bipyramids that share corners with eight equivalent SbIn6Sb2 hexagonal bipyramids, corners with twelve equivalent InSb6 octahedra, and edges with twelve equivalent SbIn6Sb2 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 59–121°. Both Sb–Sb bond lengths are 3.16 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on InSb by Materials Project

InSb is Wurtzite structured and crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. In3+ is bonded to four equivalent Sb3- atoms to form corner-sharing InSb4 tetrahedra. There are three shorter (2.87 Å) and one longer (2.89 Å) In–Sb bond lengths. Sb3- is bonded to four equivalent In3+ atoms to form corner-sharing SbIn4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Sierpinski Structure and Electronic Topology in Bi Thin Films on InSb(111)B Surfaces

Deposition of Bi on InSb(111)B reveals a striking Sierpinski-triangle (ST)-like structure in Bi thin films. Such a fractal geometric topology is further shown to turn off the intrinsic electronic topology in a thin film. Relaxation of a huge misfit strain of about 30 to 40% between Bi adlayer and substrate is revealed to drive the ST-like island formation. A Frenkel-Kontrova model is developed to illustrate the enhanced strain relief in the ST islands offsetting the additional step energy cost. Besides a sufficiently large tensile strain, forming ST-like structures also requires larger adlayer-substrate and intra-adlayer elastic stiffnesses, and weaker intra-adlayer interatomic interactions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗