Semiconductor Nanowires Research Articles

Plausible Colloidal Methods to Synthesize Semiconductor Nanowires: Deep Study From ZnSe Nanorods

AbstractWhen the diameter of semiconductor nanowires is below the Bohr radius, confined excitons in the radial direction can freely move along the elongated axis direction, highlighting their potential for applications in quantum information and optoelectronic devices. Controlled anisotropic growth and oriented attachment are viable strategies for producing ultra‐long semiconductor nanowires with precisely controlled lengths and diameters. Anisotropic ZnSe nanorods are used as the initial seeds for the controlled anisotropic growth and oriented attachment methods. ZnSe nanorods/nanowires with limiting lengths of tens to hundreds of nanometers are produced. The advantages and limitations of semiconductor nanowires via controlled anisotropic growth and oriented attachment are summarized. The perspective for the promotion of controlled anisotropic growth and oriented attachment is discussed, which allows to promotion of the precise synthesis of semiconductor ultra‐long nanowires to develop the fundamental research and applications of ultra‐long semiconductor nanowires.

Diffusion-Induced Ordered Nanowire Growth: Mask Patterning Insights.

Innovative methods for substrate patterning provide intriguing possibilities for the development of devices based on ordered arrays of semiconductor nanowires. Control over the nanostructures' morphology in situ can be obtained via extensive theoretical studies of their formation. In this paper, we carry out an investigation of the ordered nanowires' formation kinetics depending on the growth mask geometry. Diffusion equations for the growth species on both substrate and nanowire sidewalls depending on the spacing arrangement of the nanostructures and deposition rate are considered. The value of the pitch corresponding to the maximum diffusion flux from the substrate is obtained. The latter is assumed to be the optimum in terms of the nanowire elongation rate. Further study of the adatom kinetics demonstrates that the temporal dependence of a nanowire's length is strongly affected by the ratio of the adatom's diffusion length on the substrate and sidewalls, providing insights into the proper choice of a growth wafer. The developed model allows for customization of the growth protocols and estimation of the important diffusion parameters of the growth species.

High‐Performance Flexible Silicon Nanowire Field Effect Transistors on Plastic Substrates

AbstractInorganic semiconductor nanowires, known for their exceptional electronic properties and mechanical flexibility, are widely regarded as the ideal 1D channel materials for creating high‐performance flexible electronics. In this work, the integration of ordered arrays of silicon nanowire (SiNW) field effect transistors (FETs) directly onto flexible plastic substrates is showcased. The self‐aligned crystalline SiNW multi‐channels are first grown through an in‐plane solid–liquid–solid mechanism on rigid substrates, and then efficiently transferred in‐batch onto flexible polyethylene terephthalate (PET) plastics. The FETs constructed on these transferred SiNW channels exhibit outstanding performance, with a high on/off current ratio of >105, a low subthreshold swing of 175 mV dec−1, and remarkable mechanical stability that can endure an extremely small bending radius of 0.5 mm for 1000 cycles. Furthermore, inverter logics are also successfully demonstrated on plastic substrates, highlighting a prominent routine for scalable integration of high‐quality SiNW channels in the development of low‐cost, high‐performance flexible displays and wearable electronics.

Selective area epitaxy of in-plane HgTe nanostructures on CdTe(001) substrate

Semiconductor nanowires (NWs) are believed to play a crucial role for future applications in electronics, spintronics and quantum technologies. A potential candidate is HgTe but its sensitivity to nanofabrication processes restrain its development. A way to circumvent this obstacle is the selective area growth technique. Here, in-plane HgTe nanostructures are grown thanks to selective area molecular beam epitaxy on a semi-insulating CdTe substrate covered with a patterned SiO2mask. The shape of these nanostructures is defined by the in-plane orientation of the mask aperture along the <110>, <11¯0>, or <100> direction, the deposited thickness, and the growth temperature (GT). Several micron long in-plane NWs can be achieved as well as more complex nanostructures such as networks, diamond structures or rings. A good selectivity is achieved with very little parasitic growth on the mask even for a GT as low as 140 °C and growth rate up to 0.5 monolayer per second. For <110> oriented NWs, the center of the nanostructure exhibits a trapezoidal shape with {111}B facets and two grains on the sides, while <11¯0> oriented NWs show {111}A facets with adatoms accumulation on the sides of the top surface. Transmission electron microscopy observations reveal a continuous epitaxial relation between the CdTe substrate and the HgTe NW. Measurements of the resistance with four-point scanning tunneling microscopy indicates a good electrical homogeneity along the main NW axis and a thermally activated transport. This growth method paves the way toward the fabrication of complex HgTe-based nanostructures for electronic transport measurements.

Sodium-based plasmonic waveguides with high confinement factors and ultra-low gain thresholds.

The noble metal-based hybrid plasmon mode features low loss and strong field localization, making it widely applicable in the field of nanophotonic devices. However, due to the high loss of noble metals, the gain threshold is unacceptably high, usually larger than 0.1 µm-1. Here we present a hybrid plasmonic waveguide consisting of a SiO2 layer coated Na nanowire and a hexagonal semiconductor nanowire. Based on the high performance of the proposed waveguide, the Purcell factor exceeding 120 and a confinement factor above 90% are achieved, leading to an ultra-low gain threshold of 0.02117 µm-1. In addition, the proposed waveguide exhibits an extremely low cross talk, making it highly suitable for applications in compact photonic integrated devices. The proposed waveguide may contribute to the development of low-threshold nano-lasers and promote other applications in nanophotonics.

Materials for semiconductor nanowires in nanoscale photonic and electronic devices

Abstract Many aspects of civilization are impacted by electronic and optoelectronic equipment, including medical instruments, communications, computing, multimedia systems, and basic home appliances. the development of nanoscale devices has garnered significant attention due to the increasing demand for smaller, more powerful, and efficient systems across various industries. Nanoscale devices operate at the nanometer scale, typically involving structures and components with dimensions on the order of 1 to 100 nanometers. As a potent class of materials, semiconductor nanowires are creating a lot of new possibilities for innovative nanoscale photonic and electrical devices through carefully regulated development and organization. the exploration of electronic and optoelectronic nanodevices, along with integrated arrays, opens up a rich landscape of possibilities across various technological domains. This research not only pushes the boundaries of miniaturization but also paves the way for innovative applications in electronics, photonics, sensing, and emerging fields like quantum and neuromorphic computing that hold the potential for numerous applications in the future.

High-quality thickness-tunable InAs nanowire crosses grown by molecular-beam epitaxy

InAs nanowire crosses show great potential applications in detection and braiding of Majorana zero modes. Controlled growth of high-quality and diameter tunable InAs nanowire crosses is fundamental for these applications. However, it is still difficult to freely and conveniently adjust the diameter of the free-standing InAs nanowire crosses grown by the conventional growth methods. Here, we report a new technique to realize the growth of high-quality thickness-tunable InAs nanowire crosses by molecular-beam epitaxy. GaAs nanowire crosses were firstly grown on the Si (100) substrates spontaneously by merging the <111>-oriented GaAs nanowires. InAs nanowire crosses were then obtained by in situ growth of InAs shells on the facets of GaAs nanowire cross cores. Detailed scanning and transmission electron microscopic observations and energy dispersive spectrum analyses confirm that the InAs nanowire crosses grown by this manner have continuous and smooth morphology and they are high-quality zinc-blende crystals. More importantly, the InAs shell is grown with the vapor-solid growth mechanism and the thickness of the InAs nanowire crosses can be tuned by varying the InAs shell growth time. Our work provides a valuable method for the controlled growth of thickness-tunable semiconductor nanowire crosses.

Geometric Symmetry Breaking and Nonlinearity Can Increase Thermoelectric Power.

Direct thermal-to-electric energy converters typically operate in the linear regime, where the ratio of actual maximum power relative to the ideal maximum power, the so-called fill factor (FF), is 0.25. Here, we show, based on fundamental symmetry considerations, that the leading order nonlinear terms that can increase the FF require devices with broken spatial symmetry. Studying nonlinear, thermoelectric transport across an asymmetric energy barrier defined in a single semiconductor nanowire, we find in both experiment and theory that we can increase the FF as well as maximum power. Geometric symmetry breaking combined with the design of nonlinear behavior thus represents a strategy for increasing the performance of thermoelectric or hot-carrier devices.

Imaging of Volatile Organic Compounds Using a Single Nanowire-Based Electronic Nose for Future Biomedical Applications.

This study introduces an array of semiconductor oxide single nanowires fabricated using advanced semiconductor processing techniques, including electron beam lithography and thin-film deposition, which is well-suited for large-scale nanowire integration. A four-channel nanowire array consisting of tin oxide (SnO2), indium oxide (In2O3), ferric oxide (Fe3O4), and titanium oxide (TiO2) was developed. As a proof of concept, we converted the response curves of the sensor array to heat maps, enabling comprehensive feature representation. The fabricated electronic nose (E-nose) was utilized to detect three types of volatile organic compounds (VOCs), with the results visualized in a heat map format. Additionally, the performance of each individual sensor was quantitatively studied, highlighting the array's potential for enhanced gas detection and analysis. To further illustrate the interaction between gas molecules and the nanowires, we visualized the gas response results by mapping the sensor's signal changes. These visualizations provide a clear representation of how different gas molecules interact with specific nanowires. For example, the heat maps reveal distinct response patterns for each type of VOC, allowing for the identification and differentiation of gases based on their unique signatures. This visualization technique not only enhances the understanding of gas-nanowire interactions but also demonstrates the effectiveness of the E-nose in distinguishing between various VOCs. The SnO2 nanowire gas sensor showed enhanced gas response compared to other materials. The SnO2 and TiO2 gas sensors showed enhanced response (62 and 56 s) and recovery times (100 and 37 s).

Optoelectronic synapses with chemical-electric behaviors in gallium nitride semiconductors for biorealistic neuromorphic functionality

Optoelectronic synapses, leveraging the integration of classic photo-electric effect with synaptic plasticity, are emerging as building blocks for artificial vision and photonic neuromorphic computing. However, the fundamental working principles of most optoelectronic synapses mainly rely on physical behaviors while missing chemical-electric synaptic processes critical for mimicking biorealistic neuromorphic functionality. Herein, we report a photoelectrochemical synaptic device based on p-AlGaN/n-GaN semiconductor nanowires to incorporate chemical-electric synaptic behaviors into optoelectronic synapses, demonstrating unparalleled dual-modal plasticity and chemically-regulated neuromorphic functions through the interplay of internal photo-electric and external electrolyte-mediated chemical-electric processes. Electrical modulation by implementing closed or open-circuit enables switching of optoelectronic synaptic operation between short-term and long-term plasticity. Furthermore, inspired by transmembrane receptors that connect extracellular and intracellular events, synaptic responses can also be effectively amplified by applying chemical modifications to nanowire surfaces, which tune external and internal charge behaviors. Notably, under varied external electrolyte environments (ion/molecule species and concentrations), our device successfully mimics chemically-regulated synaptic activities and emulates intricate oxidative stress-induced biological phenomena. Essentially, we demonstrate that through the nanowire photoelectrochemical synapse configuration, optoelectronic synapses can be incorporated with chemical-electric behaviors to bridge the gap between classic optoelectronic synapses and biological synapses, providing a promising platform for multifunctional neuromorphic applications.

3D Shape Reconstruction of Ge Nanowires during Vapor-Liquid-Solid Growth under Modulating Electric Field.

Bottom-up growth offers precise control over the structure and geometry of semiconductor nanowires (NWs), enabling a wide range of possible shapes and seamless heterostructures for applications in nanophotonics and electronics. The most common vapor-liquid-solid (VLS) growth method features a complex interaction between the liquid metal catalyst droplet and the anisotropic structure of the crystalline NW, and the growth is mainly orchestrated by the triple-phase line (TPL). Despite the intrinsic mismatch between the droplet and the NW symmetries, its discussion has been largely avoided because of its complexity, which has led to the situation when multiple observed phenomena such as NW axial asymmetry or the oscillating truncation at the TPL still lack detailed explanation. The introduction of an electric field control of the droplet has opened even more questions, which cannot be answered without properly addressing three-dimensional (3D) structure and morphology of the NW and the droplet. This work describes the details of electric-field-controlled VLS growth of germanium (Ge) NWs using environmental transmission electron microscopy (ETEM). We perform TEM tomography of the droplet-NW system during an unperturbed growth, then track its evolution while modulating the bias potential. Using 3D finite element method (FEM) modeling and crystallographic considerations, we provide a detailed and consistent mechanism for VLS growth, which naturally explains the observed asymmetries and features of a growing NW based on its crystal structure. Our findings provide a solid framework for the fabrication of complex 3D semiconductor nanostructures with ultimate control over their morphology.

Quantum Dots and Molecular Junctions as Energy Filters for Thermal-to-Electric Energy Conversion

The thermoelectric conversion of heat into electricity requires a form of energy filtering, that allows hot electrons to pass while blocking cold electrons. The energy conversion efficiency is determined by the details of the energy filtering, with an infinitely sharp (delta function) transmission spectrum allowing near ideal (Carnot) efficiency. [1]I will introduce this concept and report on a proof-of-performance experiment based on a quantum dot embedded into a single, semiconductor nanowire. This near-ideal quantum-dot heat engine realized power production at maximum power with Curzon-Ahlborn efficiency as well more than 70% of Carnot efficiency at maximum efficiency settings [2].To further enhance efficiency at maximum power one wishes to shape the transmission function to allow a spectrum of warmer electrons to pass while still completely blocking cold electrons. This may be achieved by exploiting quantum interference phenomena to block low-energy electron transmission by destructive interference, and to thus sculpt the transmission function of quantum dots or molecular junctions.[4] In contrast to quantum dots, molecular junctions have the advantage that they can be used at room temperature and can be produced, in principle, cheaply and scalable. To systematically explore the effect of quantum interferences, we designed and synthesized a new class of porphyrins that are expected to feature destructive quantum interference in single molecule junctions with gold electrodes and may thus show high thermopower, as well as a control that does not. We performed detailed experimental single-molecule break-junction studies of conductance and thermopower on porphyrin molecular junctions. We find a somewhat better thermoelectric performance for the porphyrin where we expect destructive interference. However, the predicted large difference in conductance and thermopower is not supported by our experimental findings.[4]Finally, I will also briefly discuss the potential application of the concepts and systems presented here in hot-carrier photovoltaics, as an approach to increasing photovoltaic energy conversion efficiency beyond current limits.[1] T.E. Humphrey et al., Reversible Quantum Brownian Heat Engines for Electrons. Phys. Rev. Lett., 89, 116801 (2002)[2] M. Josefsson et al. A quantum-dot heat engine operated close to thermodynamic efficiency limits. Nature Nanotechn. 13, 920 (2018)[3] O Karlström et al. Increasing thermoelectric performance using coherent transport. Phys. Rev. B 84, 113415 (2011)[4] H. Xu et al. Electrical Conductance and Thermopower of β-Substituted Porphyrin Molecular Junctions Synthesis and Transport. JACS 145 , 23541 (2023) Figure 1

Controlled Assembly of Nanowires into Welded Nanowire Networks for Memristor Device Fabrication

Next-generation electronic devices are essential for neuromorphic computing (or brain-inspired computing), which is essential for the high-speed processing of big data using artificial intelligence tools.(1) Memristors, an important constituent of these next-generation electronic devices, have been fabricated using many forms of metal oxides, including nanowires. Nanowires forms of oxides, although reduce the complexity of the memristive device fabrication process, need many technological advances for their widespread use in memristor fabrication.(1) For instance, the cyclability of devices needs to be improved. Furthermore, realizing the high density of nanowire-based memristor devices requires methods for addressing individual nanowires in large assemblies (i.e., arrays) of nanowires, strategies for which also need to be developed.(1) A possible avenue to address these problems is through the use of nanowire networks,(1) specifically those that have nanowires welded together via bridges that have the same chemical composition as those of the nanowires themselves.(2) In this configuration, the resistive switching of both the nanowires and the randomly-formed junctions between the nanowires can be employed to make mesoscale devices, circumventing the need to individually address each nanowire in the nanowire assemblies.(1) Realizing memristive devices based on welded nanowire networks, therefore, requires a strategy for assembly via welding of pre-synthesized nanowires into networks that offer the ability to control the chemical compositions of the interfaces between the nanowires and the densities of nanowires within the assemblies.(2, 3) In the presentation, strategies developed by our group for the assembly of semiconductor nanowires into welded nanowire networks of controlled densities will be discussed in detail. Specific devices that will be discussed include assembly via welding of Mg2Si, TiO2 and TiC nanowires.(2, 3) The assembly via welding of nanowires into networks is expected to accelerate the testing of mesoscale memristive devices, irrespective of the method employed for the synthesis of the nanowires used in the assemblies. This is expected to aid in accelerating both the science and technology needed for the deployment of memristive devices.

(Invited) Photoluminescence Properties of Single InAsP Quantum Dots Embedded in InP Nanowires

Non-classical light emitters that can generate single photons with a negligible multiphoton probability are one of the key components for quantum information technologies. Deterministically grown III-V semiconductor nanowires containing quantum dots are gaining interest as a viable platform for quantum key distribution applications. In this talk, we will report on our recent development of the fabrication of InAsP single quantum dots embedded within InP photonic waveguide nanowires. In particular, we outline the importance of the photonic waveguide design for optimum photon generation and coupling to external optics [1]. The measured count rate dependence on normalized wire diameter, D/λ (figure 1) of the nanowire sources is consistent with calculations of the spontaneous emission rate into the fundamental HE11 nanowire waveguide mode (ΓHE11). Manipulating dot growth conditions and engineering the band structure around the dot (dot-in-a-rod configuration) are applied [2] to enhance the photoluminescence emission rate at 1310 nm and 1550 nm. Single photon emission with very low multiple photon probability is demonstrated at O- and C-band [3,4]. Temperature dependent, second-order correlation measurements on the 1310 nm source show that these nanowire sources can generate single photons up to temperatures of 220 K [3].[1] S. Haffouz, et al., Nano Letters, 18, 3047 (2018).[2] S. Haffouz, et al., Applied Physics Letters, 117, 113101 (2020).[3] P. Laferriére, et al., Nano Letters, 23, 962 (2023).[4] A.N. Wakileh, et al., arXiv:2309.13381 (2023). Figure 1

Room-Temperature Near-Infrared Lasing from GaAs/AlGaAs Core-Shell Nanowires Based on Random Cavity.

Room-temperature lasing based on low-dimensional GaAs nanowires (NWs) is one of the most critical and challenging issues in realizing near-infrared lasers for nanophotonics. In this article, the random lasing characteristics based on GaAs NW arrays have been discussed theoretically. According to the simulation, GaAs/AlGaAs core-shell NWs with an optimal diameter, density, and Al content in the shell have been grown. Systematic morphological and optical characterizations were carried out. It is found that the GaAs NWs with the additional growth of the AlGaAs shell exhibit improved emission by about 2 orders of magnitude at low temperatures, which can be attributed to the suppression of crystal defects. At room temperature, lasing was observed with a threshold around 70.16 mW/cm2, and the random lasing mechanism was discussed in detail. This work is of great significance for the design of random cavities based on semiconductor NWs, which is important for optoelectronic integration.

Josephson Diode Effect in Parallel-Coupled Double-Quantum Dots Connected to Unalike Majorana Nanowires.

We study theoretically the Josephson diode effect (JDE) when realized in a system composed of parallel-coupled double-quantum dots (DQDs) sandwiched between two semiconductor nanowires deposited on an s-wave superconductor surface. Due to the combined effects of proximity-induced superconductivity, strong Rashba spin-orbit interaction, and the Zeeman splitting inside the nanowires, a pair of Majorana bound states (MBSs) may possibly emerge at opposite ends of each nanowire. Different phase factors arising from the superconductor substrate can be generated in the coupling amplitudes between the DQDs and MBSs prepared at the left and right nanowires, and this will result in the Josephson current. We find that the critical Josephson currents in positive and negative directions are different from each other in amplitude within an oscillation period with respect to the magnetic flux penetrating through the system, a phenomenon known as the JDE. It arises from the quantum interference effect in this double-path device, and it can hardly occur in the system of one QD coupled to MBSs. Our results also show that the diode efficiency can reach up to 50%, but this depends on the overlap amplitude between the MBSs, as well as the energy levels of the DQDs adjustable by gate voltages. The present model is realizable within current nanofabrication technologies and may find practical use in the interdisciplinary field of Majorana and Josephson physics.

Contact Geometry-Dependent Excitonic Emission in Mixed-Dimensional van der Waals Heterostructures.

Manipulation of excitonic emission in two-dimensional (2D) materials via the assembly of van der Waals (vdW) heterostructures unlocks numerous opportunities for engineering their photonic and optoelectronic properties. In this work, we introduce a category of mixed-dimensional vdW heterostructures, integrating 2D materials with one-dimensional (1D) semiconductor nanowires composed of vdW layers. This configuration induces spatially distinct localized excitonic emissions through a tailored interfacial heterolayer atomic arrangement. By precisely adjusting both the axial and sidewall facet orientations of bottom-up grown PbI2 vdW nanowires and by transferring them onto 1L WSe2 flakes, we establish vdW heterointerfaces with either perpendicular or parallel interatomic arrangements. The edge-standing heterojunction, featuring perpendicular PbI2 layers atop WSe2, promotes efficient charge transfer through the edges and coupled localized states, leading to an enhanced redshifted excitonic emission. Conversely, the layer-by-layer heterointerface, where PbI2 layers are in parallel contact with WSe2, exhibits substantial quenching due to deep midgap states in a type-II alignment, as evidenced by power-dependent measurements and first-principle calculations. Our results introduce a method for actively manipulating excitonic emissions in 2D transition metal dichalcogenides (TMDs) through edge engineering, highlighting their potential in the development of various quantum devices.

SYNTHESIS AND STUDY OF OPTICAL, ELECTRICAL PROPERTIES OF TIN DIOXIDE NANOWIRES IN A SiO&lt;sub&gt;2&lt;/sub&gt;/Si TRACK TEMPLATE

This work presents a study of the structural, optical and electrical characteristics of tin dioxide (SnO2) nanowires obtained by chemical deposition (CD) into a SiO2/Si track template (template synthesis). Latent tracks in the SiO2 layer were created by irradiation with swift heavy ions (SHI) of Xe at an energy of 200 MeV with a fluence of Ф = 108 cm−2 and subsequent etching in a 4% aqueous solution of hydrofluoric acid (HF). The chosen CD method is widely used for the deposition of semiconductor oxide nanowires in SiO2 nanopores. The CD method is cost-effective because it does not require special equipment for deposition of nanowires. To carry out deposition, a solution of a coordination compound of a metal and a reducing agent is used. To analyze the filling of pores after the CD process, the surface morphology of the samples was studied using a Zeiss Crossbeam 540 scanning microscope. The crystallographic structure of SnO2/SiO2/Si nanostructures with SnO2 nanopore filling was studied by X-ray diffraction. X-ray diffraction analysis (XRD) is carried out on a Rigaku SmartLab X-ray diffractometer. As a result, a SnO2-NW/SiO2/Si nanoheterostructure with an orthorhombic crystal structure of SnO2 nanowires was obtained. Photoluminescence (PL) spectra were measured upon excitation with light at a wavelength of 240 nm using a CM2203 spectrofluorimeter (Solar). Gaussian decomposition of the photoluminescence spectrum of SnO2-NW/SiO2/Si structures showed that they have low intensity, which is mainly due to the presence of defects such as oxygen vacancies, interstitial tin or tin with damaged bonds. Electrical characterization studies were performed using a VersaStat 3 potentiostat (Ametek). Measurement of the current-voltage characteristic showed that the resulting SnO2-NW/SiO2/Si nanoheterostructure contains arrays of p-n junctions.

Energy Levels of Nanodots Inside Semiconductor Nanowires

Energy Levels of Nanodots Inside Semiconductor Nanowires

Comparing the mean inner potential of Zn-VI semiconductor nanowires using off-axis electron holography

The mean inner potential (MIP), V 0, for a series of Zn group VI semiconductor nanostructures were measured experimentally using off-axis electron holography. Values for ZnS, ZnTe and ZnO were remeasured and new values were added for ZnSe and ZnSSe nanowires. We confirm that the MIP increases non-linearly with mass density beginning at 12.4 ± 0.2 V for the lowest density ZnS and slowly increasing with composition to 12.9 ± 0.2 V for ZnSe, more rapidly for ZnTe and with a significant increase to 14.8 ± 0.3 V for ZnO with the highest density. Published results from DFT calculations compared well to these measurements with similar trends apparent for other cation families such as the Ga-III-V.