Sb Nanowires Research Articles

Spatial dependence of dopant incorporation and electrical transport in Si-doped GaAs(Sb) nanowires

Spatial dependence of dopant incorporation and electrical transport in Si-doped GaAs(Sb) nanowires

Template-assisted electrodeposition of freestanding antimony, tin, and antimony-tin nanowire arrays from an ionic liquid

In the present study, we show the electrochemical synthesis of Sb, Sn, and Sb-Sn nanowire arrays from the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonate ([Py1,4]TfO) via templated-assisted approaches. Commercially available track etched polycarbonate template with a nominal pore diameter of 400 nm was utilized as a template. The nanowires were electrochemically deposited inside the pores of the template; then, a supporting copper layer was electrodeposited on the back side of the template. Subsequently, the template was dissolved with dichloromethane, and the structural morphology of the nanowire structures was explored by high-resolution scanning electron microscopy (SEM) and energy dispersive x-ray (EDX). Freestanding, mechanically stable nanowire arrays of Sb, Sn, and Sb-Sn with an average pore diameter of 400 nm were obtained. The charge/discharge characteristics of the electrodeposited nanowire films were investigated to explore the Li storage capacity of the fabricated electrodes. The results revealed that the electrodeposited nanowire films are promising anode candidates for the future generation of Li-ion batteries.Graphical abstract

Axial Growth Characteristics of Optically Active InGaAs Nanowire Heterostructures for Integrated Nanophotonic Devices.

III-V semiconductor nanowire (NW) heterostructures with axial InGaAs active regions hold large potential for diverse on-chip device applications, including site-selectively integrated quantum light sources, NW lasers with high material gain, as well as resonant tunneling diodes and avalanche photodiodes. Despite various promising efforts toward high-quality single or multiple axial InGaAs heterostacks using noncatalytic growth mechanisms, the important roles of facet-dependent shape evolution, crystal defects, and the applicability to more universal growth schemes have remained elusive. Here, we report the growth of optically active InGaAs axial NW heterostructures via completely catalyst-free, selective-area molecular beam epitaxy directly on silicon (Si) using GaAs(Sb) NW arrays as tunable, high-uniformity growth templates and highlight fundamental relationships between structural, morphological, and optical properties of the InGaAs region. Structural, compositional, and 3D-tomographic characterizations affirm the desired directional growth along the NW axis with no radial growth observed. Clearly distinct luminescence from the InGaAs active region is demonstrated, where tunable array-geometry parameters and In content up to 20% are further investigated. Based on the underlying twin-induced growth mode, we further describe the facet-dependent shape and interface evolution of the InGaAs segment and its direct correlation with emission energy.

Magnetic properties of Mn-doped InSb nanowires from first principles

Room-temperature ferromagnetism (RTFM) has been achieved in Mn-doped InSb nanowires (NWs) through experiment. However, the underlying cause of RTFM remains unclear. In this paper, using first-principles calculations, the distribution of Mn ions and magnetic properties of Mn-doped wurtzite and zinc blend InSb NWs have been investigated. Our results indicate that wurtzite (In,Mn)Sb NWs can exhibit superior ferromagnetic behavior compared to zinc blend (In,Mn)Sb NWs. The distribution of Mn ions and magnetic properties in the (In,Mn)Sb NWs is influenced by their size, surface passivation and crystal structure. Furthermore, the ferromagnetic coupling is short-range in passivated (In,Mn)Sb NWs, and as the size of the NW decreases, the Mn-3d level becomes a deep acceptor in the band gap, resulting in an enhancement of ferromagnetism.

Influence of High Surfactant Concentrations on the Morphology and Crystallinity of Electrodeposited Antimony and Bismuth Nanowires

Antimony and bismuth nanowires are excellent model systems to investigate the interplay of various size-dependent transport phenomena relevant for applications in thermoelectrics, spintronics, or catalysis. The properties of these nanowires can be significant influenced by size effects due to the large mean free path and Fermi wavelength of charge carriers and phonons. Since antimony and bismuth possess highly anisotropic Fermi surfaces, the transport is also strongly dependent on the crystallographic orientation. Therefore, it is very important to develop and control suitable electrodeposition processes that allow us to understand the nanowire growth and to accordingly adjust preferred orientation and morphology of the synthesized nanowires.The so called template route employed in the presented work allows to control number density, alignment, geometry, length and diameter of the nanowires. The electrolytes and plating processes influence crystallinity, crystal orientation, and morphology of the electrodeposited materials. Here, antimony and bismuth nanowires are grown by potentiostatic electrodeposition in polycarbonate etched ion-track membranes using SbCl3 and BiCl3 in aqueous electrolytes.In this talk, we will show the influence of the presence of nonionic and anionic surfactants in high concentrations in the electrolyte during the electrodeposition of Bi and Sb nanowires. The recorded current-time curves of the plating process will be presented. Systematic characterization of the nanowires by scanning- and transmission electron microscopy, and X-ray diffraction reveal a strong change in crystallinity as a function of surfactant concentration, which will be discussed in detail.

Theoretical approach to the phonon modes of GaSb nanowires

Gallium Antimonide nanowires (GaSbNWs) have attracted much attention due to their possible applications in mid infrared detectors, however, there are only few theoretical investigations about this material and almost none regarding its vibrational properties. In this work the phonon modes of GaSbNWs were studied using the density functional theory with the finite displacement supercell scheme. The nanowires are modeled by removing atoms outside from a circumference along the [1 1 1] direction. All surface dangling bonds were passivated with hydrogen atoms. The results show that the expected red-shift of the highest frequency modes of GaSb are hindered by low frequency H bond bending modes. Three clearly distinguishable frequency intervals were observed: One with vibrations whose main contribution come from the Ga and Sb nanowire atoms, the second interval with main contributions from H bending modes and finally a high frequency interval where the main contributions come from H stretching modes. Also, it was observed that the radial breathing mode (RBM) decreases when the nanowire diameter increases, while the contrary tendency is observed with their specific heat (the specific heat increases as the nanowire diameter increases), except in the low temperature region where the lower diameters have higher specific heat values. These results could be important for the characterization of these nanowires with IR and Raman techniques.

Enhanced growth and properties of non-catalytic GaAs nanowires via Sb surfactant effects

We report the effects of antimony (Sb) surfactant on the growth and correlated structural and optical properties of non-catalytic GaAs nanowires (NW) grown by selective area epitaxy on silicon. Strong enhancements in the axial growth with very high aspect ratio up to 50 are observed by the addition of small traces of Sb (1%–2%), contrasting the commonly reported growth limiting behavior of Sb in GaAs(Sb) NWs. The Sb surfactant effect modifies the growth facet structure from a pyramidal-shaped growth front terminated by {1–1–0} planes to a flat (111)B growth plane, that is even further improved by the presence of Si co-dopants. Additional benefits are seen by the substantial change in microstructure, from a heavily defected layer stacking in Sb-free GaAs NWs to a twinned phase-pure zinc blende structure in Sb-mediated GaAs(Sb) NWs. We directly confirm the impact of the altered microstructure on the optical emission and carrier recombination dynamics via observation of long, few-ns carrier lifetimes in the GaAs(Sb) NWs using steady-state and time-resolved photoluminescence spectroscopy.

Amorphous TiO2-x modified Sb nanowires as a high-performance sodium-ion battery anode

A simple synthesis has been proposed for seaweed-like amorphous TiO2-x modified Sb (a-TiO2-x/Sb) composite nanowires as sodium-ion battery (SIBs) anodes by a dealloying method of Al-Sb-Ti alloys. Compared with other conventional methods, this method has the advantages of simple preparation, high yield and easy large-scale synthesis. It is excitingly discovered that a-TiO2-x/Sb effectively alleviates volume changes and stabilizes the solid electrolyte interface (SEI). The a-TiO2-x/Sb nanowires electrodes deliver outstanding electrochemical performance based on the synergistic effects, exhibiting a high reversible capacity of 591.9 mA h g−1 at 100 mA g−1, stable cycling performance with a high capacity retention of 96.4% after 200 cycles and superior rate capability 382.2 mA h g−1 at 10,000 mA g−1, which is very competitive among the reported Sb-based anodes.

In-plane InGaAs/Ga(As)Sb nanowire based tunnel junctions grown by selective area molecular beam epitaxy

In-plane InGaAs/Ga(As)Sb heterojunction tunnel diodes are fabricated by selective area molecular beam epitaxy with two different architectures: either radial InGaAs core/Ga(As)Sb shell nanowires or axial InGaAs/GaSb heterojunctions. In the former case, we unveil the impact of strain relaxation and alloy composition fluctuations at the nanoscale on the tunneling properties of the diodes, whereas in the latter case we demonstrate that template assisted molecular beam epitaxy can be used to achieve a very precise control of tunnel diodes dimensions at the nanoscale with a scalable process. In both cases, negative differential resistances with large peak current densities are achieved.

Resolving few-layer antimonene/graphene heterostructures

Two-dimensional (2D) antimony (Sb, “antimonene”) is of interest in electronics and batteries. Sb however exhibits a large allotropic structural diversity, which is also influenced by its support. Thus, Sb heterostructure formation is key in 2D Sb integration. Particularly, 2D Sb/graphene interfaces are important. We thus study here few-layered 2D Sb/graphene heterostructures with atomic resolution (scanning) transmission electron microscopy. We find two Sb morphologies to coexist: first, a 2D morphology of layered β-Sb with β-Sb(001)||graphene(001) texture. Second, one-dimensional Sb nanowires which can be matched to β-Sb[2-21]⊥graphene(001) and are closely related to cubic Sb(001)||graphene(001). Importantly, both Sb morphologies show rotational van-der-Waals epitaxy with graphene. Both are resilient against oxidation, although superficial Sb-oxide formation merits consideration, including epitaxial Sb2O3(111)/β-Sb(001) heterostructures. Exact Sb growth behavior depends on processing and substrate properties including, notably, the support underneath the graphene. Our work elucidates the rich phase and epitaxy landscape in 2D Sb and 2D Sb/graphene heterostructures.

Recent Progress on the Gold-Free Integration of Ternary III-As Antimonide Nanowires Directly on Silicon.

During the last few years, there has been renewed interest in the monolithic integration of gold-free, Ternary III–As Antimonide (III–As–Sb) compound semiconductor materials on complementary metal-oxide-semiconductor (CMOS)—compatible silicon substrate to exploit its scalability, and relative abundance in high-performance and cost-effective integrated circuits based on the well-established technology. Ternary III–As–Sb nanowires (NWs) hold enormous promise for the fabrication of high-performance optoelectronic nanodevices with tunable bandgap. However, the direct epitaxial growth of gold-free ternary III–As–Sb NWs on silicon is extremely challenging, due to the surfactant effect of Sb. This review highlights the recent progress towards the monolithic integration of III–As–Sb NWs on Si. First, a comprehensive and in-depth review of recent progress made in the gold-free growth of III–As–Sb NWs directly on Si is explicated, followed by a detailed description of the root cause of Sb surfactant effect and its influence on the morphology and structural properties of Au-free ternary III–As–Sb NWs. Then, the various strategies that have been successfully deployed for mitigating the Sb surfactant effect for enhanced Sb incorporation are highlighted. Finally, recent advances made in the development of CMOS compatible, Ternary III–As–Sb NWs based, high-performance optoelectronic devices are elucidated.

Ultra-fast photodetectors based on high-mobility indium gallium antimonide nanowires

Because of tunable bandgap and high carrier mobility, ternary III-V nanowires (NWs) have demonstrated enormous potential for advanced applications. However, the synthesis of large-scale and highly-crystalline InxGa1−xSb NWs is still a challenge. Here, we achieve high-density and crystalline stoichiometric InxGa1−xSb (0.09 < x < 0.28) NWs on amorphous substrates with the uniform phase-purity and <110 >-orientation via chemical vapor deposition. The as-prepared NWs show excellent electrical and optoelectronic characteristics, including the high hole mobility (i.e. 463 cm2 V−1 s−1 for In0.09Ga0.91Sb NWs) as well as broadband and ultrafast photoresponse over the visible and infrared optical communication region (1550 nm). Specifically, the In0.28Ga0.72Sb NW device yields efficient rise and decay times down to 38 and 53 μs, respectively, along with the responsivity of 6000 A W−1 and external quantum efficiency of 4.8 × 106 % towards 1550 nm regime. High-performance NW parallel-arrayed devices can also be fabricated to illustrate their large-scale device integrability for next-generation, ultrafast, high-responsivity and broadband photodetectors.

Feasibility of achieving high detectivity at short- and mid-wavelength infrared using nanowire-plasmonic photodetectors with p–n heterojunctions

Photodetection at short- and mid-wavelength infrared (SWIR and MWIR) enables various sensing systems used in heat seeking, night vision, and spectroscopy. As a result, uncooled photodetection at these wavelengths is in high demand. However, these SWIR and MWIR photodetectors often suffer from high dark current, causing them to require bulky cooling accessories for operation. In this study, we argue for the feasibility of improving the room-temperature detectivity by significantly suppressing dark current. To realize this, we propose using (1) a nanowire-based platform to reduce the photoabsorber volume, which in turn reduces trap state population and hence generation-recombination current, and (2) p–n heterojunctions to prevent minority carrier diffusion from the large bandgap substrate into the nanowire absorber. We prove these concepts by demonstrating a comprehensive three-dimensional photoresponse model to explore the level of detectivity offered by vertical InAs(Sb) nanowire photodetector arrays with self-assembled plasmonic gratings. The resultant electrical simulations show that the dark current can be reduced by three to four orders at room temperature, leading to a peak detectivity greater than 3.5 × 1010 cm Hz1/2 W−1 within the wavelength regime of 2.0–3.4 μm, making it comparable to the best commercial and research InAs p–i–n homojunction photodiodes. In addition, we show that the plasmonic resonance peaks can be easily tuned by simply varying the exposed nanowire height. Finally, we investigate the impact of nanowire material properties, such as carrier mobility and carrier lifetime, on the nanowire photodetector detectivity. This work provides a roadmap for the electrical design of nanowire optoelectronic devices and stimulates further experimental validation for uncooled photodetectors at SWIR and MWIR.

In-doped Sb nanowires grown by MOCVD for high speed phase change memories

Abstract We investigated the Phase Change Memory (PCM) capabilities of In-doped Sb nanowires (NWs) with diameters of (20-40) nm, which were self-assembled by Metalorganic Chemical Vapor Deposition (MOCVD) via the vapor-liquid-solid (VLS) mechanism. The PCM behavior of the NWs was proved, and it was shown to have relatively low reset power consumption (~ 400 μW) and fast switching capabilities with respect to standard Ge-Sb-Te based devices. In particular, reversible set and reset switches by voltage pulses as short as 25 ns were demonstrated. The obtained results are useful for understanding the effects of downscaling in PCM devices and for the exploration of innovative PCM architectures and materials.

Realization of Wurtzite GaSb Using InAs Nanowire Templates

AbstractThe crystal structure of a material has a large impact on the electronic and material properties such as band alignment, bandgap energy, and surface energies. Au‐seeded III–V nanowires are promising structures for exploring these effects, since for most III–V materials they readily grow in either wurtzite or zinc blende crystal structure. In III–Sb nanowires however, wurtzite crystal structure growth has proven difficult. Therefore, other methods must be developed to achieve wurtzite antimonides. For GaSb, theoretical predictions of the band structure diverge significantly, but the absence of wurtzite GaSb material has prevented any experimental verification of the properties. Having access to this material is a critical step toward clearing the uncertainty in the electronic properties, improving the theoretical band structure models and potentially opening doors toward application of this material. This work demonstrates the use of InAs wurtzite nanowires as templates for realizing GaSb wurtzite shell layers with varying thicknesses. The properties of the axial and radial heterointerfaces are studied at the atomic scale by means of aberration‐corrected scanning transmission electron microscopy, revealing their sharpness and structural quality. The transport characterizations point toward a positive offset in the valence bandedge of wurtzite compared to zinc blende.

Crystal-phase control of GaAs–GaAsSb core–shell/axial nanowire heterostructures by a two-step growth method

This study provides a controllable approach to grow both wurtzite and zinc-blende III–Sb nanowire heterostructures.

(Invited) Electrodeposition in Tailored Nanochannels: A Rich Plattform to Study Nanowire Growth in Confinement and to Develop Stable Functional 3D Nanowire Architectures

The implementation of nanowires and nanotubes for applications such as thermoelectrics, catalysis, plasmonics, or photoelectrochemical water splitting for hydrogen generation requires both, an excellent control on geometry, crystallinity and composition of the individual nanostructures, as well as its successful assembly into 2-D and 3-D architectures. Fabrication of 3-D nanowire superstructures by vapour–liquid–solid processes has been reported; however, it reveals a limited tunability of the relevant parameters. This talk will illustrate how the unique combination of electrodeposition and tailored nanochannel templates provides an excellent platform (i) to study and control the nanowire growth, and (ii) to synthesize 3-D nanostructure assemblies and investigate their size-dependent properties. Membranes with parallel nanochannels are fabricated by swift heavy ion irradiation and subsequent chemical etching. In addition, templates with interconnected tilted nanochannels are obtained by applying ion irradiation at several incident angles in consecutive steps. Nanochannel density and orientation, as well as diameter and geometry, are adjusted by the irradiation and etching conditions, respectively. Subsequent electrodeposition in the channels results in nanowire arrays and highly ordered 3-D nanowire ensembles of various materials. Recent developments achieved on the electrodeposition of metal (Au1-xAgx), semiconductor (ZnO and p-Cu2O) and semimetal (Sb) nanowire arrays and nanowire networks will be presented. Special emphasis will be given to the implementation of the nanowire assemblies in photoelectrochemical and thermoelectric devices, which is possible thanks to the flexibility and control offered by electrodeposition.

Thermoelectric battery based on bundles of Bi and Sb nanowires in anodic alumina matrices

A model of a microthermoelectric battery consisting of series connected thermoelectric cells of one-dimensional nanostructures formed into bundles by external contacts is proposed. The electrochemical processes of forming Bi and Sb nanowire arrays with the required dimensions and physicochemical properties in porous anodic alumina templates with large length-to-diameter ratios are studied and developed. The design and basis of the fabrication technology of microthermoelectric battery branches are developed, whose heat flow density will be controlled by the Seebeck coefficient measured at external contacts connecting the nanowire ends. It is shown that a set of parallel branches in the battery can be fabricated due to a high density of nanowire packing in a porous matrix, which will make it possible to achieve a fundamentally higher increase in the microheat meter efficiency.

Tuning growth direction of catalyst-free InAs(Sb) nanowires with indium droplets

The need for indium droplets to initiate self-catalyzed growth of InAs nanowires has been highly debated in the last few years. Here, we report on the use of indium droplets to tune the growth direction of self-catalyzed InAs nanowires. The indium droplets are formed in situ on InAs(Sb) stems. Their position is modified to promote growth in the 〈11–2〉 or equivalent directions. We also show that indium droplets can be used for the fabrication of InSb insertions in InAsSb nanowires. Our results demonstrate that indium droplets can initiate growth of InAs nanostructures as well as provide added flexibility to nanowire growth, enabling the formation of kinks and heterostructures, and offer a new approach in the growth of defect-free crystals.

Memristive Switching in Bi(1-x)Sb(x) Nanowires.

We investigated the memristive switching behavior in bismuth-antimony alloy (Bi(1-x)Sb(x)) single nanowire devices at 0.1 ≤ x ≤ 0.42. At 0.15 ≤ x ≤ 0.42, most Bi(1-x)Sb(x) single nanowire devices exhibited bipolar resistive switching (RS) behavior with on/off ratios of approximately 10(4) and narrow variations in switching parameters. Moreover, the resistance values in the low-resistance state (LRS) were insensitive to x. On the other hand, at 0.1 ≤ x ≤ 0.15, some Bi(1-x)Sb(x) single nanowire devices showed complementary RS-like behavior, which was ascribed to asymmetric contact properties. Transmission electron microscopy and elemental mapping images of Bi, Sb, and O obtained from the cross sections of the Bi(1-x)Sb(x) single nanowire devices, which were cut before and after RS, revealed that the mobile species was Sb ions, and the migration of the Sb ions to the nanowire surface brought the switch to LRS. In addition, we demonstrated that two types of synaptic plasticity, namely, short-term plasticity and long-term potentiation, could be implemented in Bi(1-x)Sb(x) nanowires by applying a sequence of voltage pulses with different repetition intervals.