Gallium Metal Research Articles

Growth of Ga<sub>2</sub>O<sub>3</sub> Nanowires by a Vapor Transport Method and their Optical Transmittance Spectra

Gallium oxide (Ga2O3) nanowires were grown on fused quartz and Si substrates by a vapor transport method of heating gallium metal at 750−1100 °C in a tube of the horizontal furnace. The obtained white colored product has shown to be the Ga2O3 nanowires with average diameters ranging from 30 to 80 nm. The optical transmittance spectra indicated that the bandgap energy of Ga2O3 nanowire increases as the diameter of nanowire decreases.

Defect-related photoluminescence of gallium nitride/silicon nanoporous pillar array modulated by ammonia gas flow rate

The structural and physical properties of silicon nanoporous pillar array (Si-NPA) make it an ideal template for preparing Si-based gallium nitride (GaN) optoelectronic devices with promising performances. For satisfying the spectral requirements in different devices, the control of the luminescence is of key importance. Here we report that utilizing Si-NPA as substrates, high-purity metal gallium as gallium source and ammonia gas as nitrogen source, GaN nanostructures were grown on Si-NPA by a chemical vapor deposition method. It was demonstrated that the photoluminescence (PL) properties of GaN/Si-NPA can be tuned effectively by changing the ammonia flow rate used during the growing process. Through analyzing the evolution of the PL spectra of GaN/Si-NPA with ammonia flow rate, the origins of the observed ultraviolet and visible PL were attributed to the near band edge emission and the emissions from Ga vacancy and N interstitial point defects, respectively. Therefore the variation of the PL spectra of GaN/Si-NPA with ammonia flow rate is actually a reflection of the change of the types and concentrations of point defects. The results might provide an efficient path for preparing Si-based GaN with controlled properties.

Unexpected Near-Infrared to Visible Nonlinear Optical Properties from 2-D Polar Metals.

Near-infrared-to-visible second harmonic generation from air-stable two-dimensional polar gallium and indium metals is described. The photonic properties of 2D metals, including the largest second-order susceptibilities reported for metals (approaching 10 nm/V), are determined by the atomic-level structure and bonding of two-to-three-atom-thick crystalline films. The bond character evolved from covalent to metallic over a few atomic layers, changing the out-of-plane metal-metal bond distances by approximately ten percent (0.2 Å), resulting in symmetry breaking and an axial electrostatic dipole that mediated the large nonlinear response. Two different orientations of the crystalline metal atoms, corresponding to lateral displacements <2 Å, persisted in separate micrometer-scale terraces to generate distinct harmonic polarizations. This strong atomic-level structure-property interplay suggests metal photonic properties can be controlled with atomic precision.

Electrocatalytic effect of 3D porous sulfur/gallium hybrid materials in lithium–sulfur batteries

Lithium–sulfur battery has long been considered as the best choice for the next generation secondary battery. However, the intrinsic insulativity of sulfur and the polysulfide shuttle effect have been the key problems that hinder the commercialization of lithium sulfur batteries. Here, using a facile shearing implement assists thermal synthesis process, in which liquid metal gallium and sulfur (mass ratio1:10) are the only reactants, we create a 3D porous sulfur/gallium hybrid materials (S/Ga). Micro/nanometer liquid metal gallium particles embed in the porous sulfur. The S/Ga cathode lithium cell exhibits a high Coulombic efficiencies of 98.7%, and high specific capacities of 1044 mAh g−1 after 100 cycles at 1.0 mA cm−2, and good cyclic stability. During first cycle discharge process of the S/Ga cathode, the sulfur reduces to Li2S8 and dissolves in the electrolyte, then the liquid metal Ga has an intimate electrical contact with conductive carbon substrates. Electrons are easily transferred to high conductive liquid metal Ga. Due to the electron abundance on Ga surface, it shows an electrocatalytic effect for the conversion of soluble lithium polysulfides (Li2S4-8) to Li2S2/Li2S, thus improving S utilization and cyclic stability.

Synthesis of Water-Soluble Copolymers of N-vinylpyrrolidone with N-vinyldithiocarbamate as Multidentate Polymeric Chelation Systems and Their Complexes with Indium and Gallium.

Dithiocarbamate (DTC) derivatives of N-vinylpyrrolidone-N-vinylamine (VP–VA) copolymers were synthesized via reaction between the copolymers and carbon disulfide in alkaline medium; molecular masses of the products were 12 and 29 kDa; the VP:VDTC ratios were 94:6 and 83:17 mol.%. Complexation between the obtained DTC derivatives and metal ions (indium and gallium) was investigated. It was demonstrated that metal–DTC ligand complexes with 1:3 ratio between components were formed. Gallium metal–polymer complexes (MPC) were unstable in solution. Individual indium MPC were isolated and characterized by spectral and chromatographic methods. Unlike similar gallium MPC, they appeared to be stable in histidine challenge reaction.

Structural and luminescence properties of GaN nanowires grown on Si substrate by Au catalyst

The synthesis of hexagonal wurtzite one-dimensional GaN nanowires on Si (111) substrate was investigated using a thermal chemical vapor deposition process. The diameter of the GaN NWs was controlled by varying the growth time using a mixture of GaN powder and gallium metal with the ammonia gas reaction. The grown GaN nanowires exhibited a hexagonal perfect wurtzite structure which has been confirmed by high resolution X-ray diffraction analysis. The morphology and elemental analysis of grown GaN nanowires has been studied by scanning electron microscopy and energy dispersive X-ray analysis. Photoluminescence spectra under the excitation of 244 nm showed a strong near band-edge emission around ~ 372 nm and a broad emission at 450–650 nm related to deep-level defects.

A Unified Electrothermal Behavior Modeling Method for Both SiC MOSFET and GaN HEMT

This article has presented a unified electrothermal behavior modeling method for both silicon carbide (SiC) metal oxide semiconductor field effect transistor ( <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> ) and gallium nitride (GaN) high electron mobility transistor (HEMT). The electrothemal behavior of these two kind of devices in both the first and the third quadrant is accurately modeled with serval compact equations. A modeling data and optimization algorithm-based parameter extraction method have been proposed to replace the previous time consuming and labor intensive one. The proposed parameter fitting algorithm is a genetic algorithm and Levenberg–Marquardt combined optimization algorithm possessing the advantages of global optimization and fast convergence speed, and modeling data can come from both datasheets and measurement. The correctness and accuracy of the proposed modeling method has been verified by simulation and experiment result. Meanwhile, it has been proved that the proposed modeling method is applicable to several commercially available SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s and GaN HEMTs.

Mechanically interlocked stretchable nanofibers for multifunctional wearable triboelectric nanogenerator

Abstract Nanofibers with good softness and high surface specific area are excellent choices for wearable triboelectric nanogenerator (TENG), despite that the deformability and durability remain challenging in seamless integration with daily textiles/clothes. Herein, we propose a physical interlocking strategy to realize a self-interlocked stretchable, breathable and waterproof nanofibers-membrane by simultaneous electrospinning of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and electrospraying of styrene-ethylene-butylene-styrene (SEBS). The electrosprayed SEBS microspheres serve as the elastic binders and hydrophobic modifiers for enhancing stretchability and waterproofness of the electrospun PVDF-HFP fibers network. By means of a printable electrode consisted of liquid metal (gallium indium tin particles) and silver flakes, a stretchable nanofibers-based TENG (SNF-TENG) with high triboelectric output (85 V, 219.66 mW m−2) and electrical durability was demonstrated, capable of harvesting energy from human motions and flowing water, powering 200 commercial LEDs and an electronic watch. The stretchable nanofibers membrane shows favorable mechanical compliance, which can be facilely integrated onto stretchable textile to fabricate textile-TENG, promising for comfortable wearable applications for power sources, smart raincoat, self-powered e-skin and tactile interactive interfaces.

The Improvement of Bonding Metal Layers in a GaAs Vertical Structure Light-Emitting Diode Package

This paper presents an investigation into the reliability of substrate bonding between metal layers and gallium arsenide vertical-injection light-emitting diodes (GaAs VLEDs). In this study, molybdenum (Mo) acts as a buffer layer between the GaAs VLED and the aluminum-based metal core printed circuit board (MCPCB). The thermal expansion coefficient (CTE) value of GaAs is approximately equal to that of the Mo layer under the substrate. This is beneficial for slowing the decay of the adhesive bond due to temperature cycling from − 40°C to 125°C for 50 cycles. The experimental results show that the use of the Mo buffer layer greatly improved the electrical and optical performance of the LED packages. The average leakage current was reduced from 33.63 mA to 2.37 mA at the reversed voltage of − 3 V and the increase in light output power was 130% at an injection current of 0.7 A. The results also show that a Mo buffer layer can reduce the risk of cracking on bonding wires after the thermal shock test (TST). These results are useful for improving the aging of GaAs VLEDs.

Transition from thin film to nanostructure in low pressure chemical vapor deposition growth of β-Ga2O3: Impact of metal gallium source

Highly crystalline β-Ga2O3 has been grown on a c-plane (0001) sapphire substrate using low-pressure chemical vapor deposition. This work has been focused on the impacts of the Gallium (Ga) concentration on the surface morphology of the β-Ga2O3 films. Formation of thin film, nanostructure, and the combination of both have been observed. However, no changes have been noticed on the X-ray diffraction peaks of β-phase with an increase in Ga vapor concentration, though different crystal orientation of the nanostructures has been found in the sample with relatively high Ga amount. The average crystallite size which has been calculated using Scherrer's formula shows an increment with Ga concentration. The bandgap has also been found to be altered with the metal concentration. The crystal quality of the nanostrctures evaluated from the Raman measurements shows good quality with low internal strain and low defects density. A small amount of Ga will tend towards the thin film growth whereas a high amount of Ga leads to the formation of different types of nano-structure on the β-Ga2O3 thin film. We propose that the nanostructures are formed through vapor-solid and vapor-liquid-solid mechanisms under the self-catalytic approach.

Exploring Electrochemical Extrusion of Wires from Liquid Metals.

Metal melt extrusion in gaseous or vacuum environments is a classical approach for forming wires. However, such extrusions have not been investigated in ionic solutions. Here, we use liquid metal (LM) gallium (Ga) and its eutectic alloy with indium (EGaIn) to explore the possibility of electrochemical extrusion of wires and study the tuning of the self-liming oxide layers as the coating for these wires formed during the process. By controlling the surface tension of the LM immersed in an electrolyte, and through the electrocapillary effect, we enable the extrusion of LM wires. The surface morphologies of LM wires and the thickness of the oxide layers are investigated when Ga and EGaIn are processed in neutral and basic electrolytes using various voltages. Taking advantage of the LM oxides, we show that LM wires offer tunable surface oxide thickness and composition using the electrochemical system and investigate the related working mechanisms. The wires are formed into patterns using an automated stage and show a self-healing capability. This work presents an unconventional method for electrochemical fabrication of LM wires, offering prospects for further research and industrial scale-up.

Morphological Features and Structural Analysis of Plerocercoids of Spirometra erinaceieuropaei (Cestoda: Diphyllobothriidae) from European Pine Marten, Martes martes (Mammalia: Mustelidae) in Ukraine

We report zoonotic Spirometra erinaceieuropaei (Rudolphi, 1819) Faust, Campbell and Kellogg, 1929 (Diphyllobothriidae), from its natural ecosystem in Europe from Martes martes in Ukraine. Scanning electron microscopy (SEM) images revealed the presence of mineral concretions in the scolex area of S. erinaceieuropaei. The combination of SEM and metal analysis using a dispersive X-ray technique to study the body surface of the plerocercoid and calcareous body–like structures has never been performed before in cestodes. Gallium ion sectioning and metal analysis were performed to study mineral concretions in cestodes for the first time. The results revealed moderate levels of calcium, phosphorus, and magnesium in the scolex and tegument of plerocercoids. Calcareous body–like structures included high levels of calcium and moderate levels of magnesium on their surface.

Reliable and Reversible Contact of Eutectic Gallium Indium and Copper Electrodes

AbstractPhysically reconfigurable electronics provide a unique method to significantly increase the range of capabilities that a single component can possess. Room temperature liquid metal gallium alloys provide this function as a fluid that can be mobilized to drastically modify electrical performance in devices, such as tunable antennas, high isolation switches, and mechanically responsive stretchable electronics. One of the most critical limitations of using gallium alloys for reconfigurable electronics is the irreversible interactions at the interface between the liquid gallium alloy and a traditional solid electrode. In this work, the effect of repeated connection/disconnection cycles on the electrical performance of eutectic gallium indium, a common liquid gallium alloy, and a copper electrode is characterized. The effects of environment, surface treatment, and method of contact between the liquid metal and the solid surface are identified. The failure mechanisms which prevent the reversibility of the electrical interface of these contacts are determined and a mitigation strategy is provided which resulted in 1000 reversible contacts with no degradation in electrical performance.

Synthesis and Characterization of Large‐Area Nanometer‐Thin β‐Ga2O3 Films from Oxide Printing of Liquid Metal Gallium

Herein, wafer‐scale Ga2O3 films are shown, which are synthesized by oxide printing of liquid metal Ga on SiO2/Si and sapphire substrates. This process enables highly uniform ≈2 nm‐thick films over ≫1 mm2 areas. The physical properties of these films (as‐deposited and after annealing in ambient conditions) are investigated. X‐ray photoelectron spectroscopy indicates that the as‐prepared films contain significant fractions (up to 8% wt) of Ga metal residue, which completely converts to Ga2O3 after annealing. Results from Raman spectroscopy confirm the presence of β‐phase in annealed samples. Transmission electron microscopy images indicate that the films are composed of polycrystalline domains. Photoluminescence is observed in all samples, depicting the typical spectrum of Ga2O3 with four emission bands. After annealing, the luminescence intensity increases across all samples, which is attributed to an enhancement in crystallinity. Also, the relative intensity of the blue emission decreases after annealing, which is consistent with a transition from bluish to greenish color in the films. This observation is associated with a change in defect population upon annealing. Overall, these results demonstrate that oxide printing of liquid metal gallium is a simple process that, upon annealing of the resulting films, leads to nanometer‐thin β‐Ga2O3 films over wafer‐scale areas.

Low-dimensional compounds containing bioactive ligands. Part XIV: High selective antiproliferative activity of tris(5-chloro-8-quinolinolato)gallium(III) complex against human cancer cell lines

Four gallium(III) complexes, [Ga(ClQ)3]⋅MeOH (1 – MeOH), [Ga(ClQ)3] (1), [Ga(BrQ)3] (2), [Ga(dIQ)3] (3) and [Ga(CQ)3] (4), were prepared (H-ClQ = 5-chloro-8-quinolinol, H-BrQ = 7-bromo-8-quinolinol, H-dIQ = 5,7-diiodo-8-quinolinol, H-CQ = 5-chloro-7-iodo-8-quinolinol) and characterised by elemental analysis, IR and NMR spectroscopy. Single crystal structure analysis of 1 – MeOH confirmed that the complex has a molecular structure with gallium(III) metal ion coordinated in mer-fashion by N- and O-donor atoms of three ClQ ligands. Stability of all complexes in DMSO was proved by 1H NMR spectroscopy. The in vitro antiproliferative activity of 1 was evaluated against the A2780, MBA-MB-231 and HCT116 cell lines. Complex 1 displays higher antiproliferative activity (IC50 values in the range 2.1–6 μm) compared to the ClQ ligand and cisplatin; and a significant selective antiproliferative potency (IC50 = 136 μm, for normal MRC5pd30 cell line). Radical scavenging experiments revealed that complex 1 exhibits the highest antioxidant activity of the prepared complexes as well as the ligands.

Embedded screen-printed transducers in bulk polymer microfluidic devices

We present a low-cost method to fabricate microfluidic devices with embedded transducers suitable for rapid prototyping on a lab scale and potentially also for mass production. To achieve this goal, a method for fabricating passive microfluidic devices using a solvent bonding technique for sealing is introduced. To avoid clogging, liquid metal (gallium) is utilized as a sacrificial layer during this bonding process. A sensor fabrication method compatible with the rapid prototyping ambitions is screen printing. Sensors based on thermal, capacitive and mechanical effects are fabricated by screen printing and are embedded into channels. The proposed processing methods can be easily adapted to achieve specific requirements associated with different tasks in lab-on-a-chip devices.

Ultrasound-assisted rapid reduction of nitroaromatics to anilines using gallium metal

The reduction of nitroaromatic compounds to anilines is widely used throughout organic synthesis. Typical methods of performing this transformation utilize hydrogenation over a pyrophoric catalyst or a finely divided reducing metal, which often affords heterogeneous mixtures that are difficult to purify. Herein, we report for the first time the use of gallium metal as a reducing agent in organic synthesis. The reaction proceeds under aerobic conditions and affords homogeneous mixtures for a convenient workup. Using this method, twelve anilines were obtained in 33% to quantitative yields with short reaction times of 10-60 minutes.

High-performance field effect transistors based on large ratio metal (Al、Ga、Cr) doped In2O3 nanofibers

Indium oxide nanofibers (In2O3 NFs) are considered to be one of the possible channel materials for future electronic devices, however, these NFs devices suffer from low on/off current ratio (Ion/Ioff), large negative threshold voltage (VTH), and high leakage current due to the excess carriers in NFs. A facile one-step electrospinning technique is employed to synthesize metal element (aluminum (Al), chromium (Cr) or gallium (Ga)) highly-doped In2O3 NFs to both improve the electrical performance of the NFs field effect transistors (FETs) and reduce the consumption of indium. The devices exhibit optimal performance at 10 mol% doping concentration (Al, Cr and Ga): small and positive VTH (<6.0 V), large Ion/Ioff (∼108), high saturation current (∼10−4 A), and decent carrier mobility (∼2.0 cm2/V−1s−1). When a high-k AlOx thin-film is employed as the gate dielectric for the NFs FETs (10 mol% Al–In2O3 NFs), the gate voltage and drain voltage is reduced to 5 V and 3 V, respectively, and the μfe is increased by 6X. Furthermore, 10 mol% Al–In2O3 NFs FETs with enhancement-mode operation were integrated into highly efficient NMOS inverters. All the results indicate that the highly metal-doped In2O3 NFs have practical application for next-generation low-cost, large-area, energy-efficient and high-performance nanoelectronic devices.

Intensification of Hydrogen Generation through Liquid Metal Gallium in Water Splitting Reaction Using Aluminum in Presence of Potassium Hydroxide

The present study reports the effect of the addition of room temperature liquid metal gallium on hydrogen generation in water splitting reaction using aluminum. The various proportions of gallium used were 13%, 23%, 33% and 50% weight by weight gallium of the total weight of metals (aluminum and gallium) in the reaction. The hydrogen generation at these additions of gallium was studied at various concentrations of aqueous KOH viz. 1 N, 1.5 N and 2 N and at various reaction temperatures of 50, 60 and 70 oC. The optimum proportion of gallium was found to be 23% at which the hydrogen generation rate was found to be thrice than the hydrogen generation rate without. The temperature of the reaction was observed to be dominant over the gallium addition at 60 and 70 oC. The gallium used in the reaction was completely recovered and reused in the reaction.

Influence of Quantum Dot Surface on Electrochemical DNA Sensing Mechanism

AbstractOwing to their high surface‐to‐volume ratio, electrocatalytic activity, biocompatibility and novel electron transport properties, quantum dots (QDs) are highly attractive materials for the ultrasensitive detection of biological macromolecules via bioelectronic devices. In this study, a QD‐based genosensor was developed, in which Ga2Te3‐based QDs were synthesized using an aqueous solution approach by mixing 3‐mercaptosuccinic acid (3MSA)‐capped gallium metal precursor with reduced tellurium metal. The results enabled us to reach an original understanding related to the active material involved in the probe DNA sensing mechanism. The morphological and structural characterization of the QDs was performed prior to their utilization in a DNA sensor construction. High‐resolution TEM (HR‐TEM) and atomic force microscopy (AFM) images confirmed the spherical and crystalline nature of the QDs, whereas X‐ray photoelectron spectroscopy (XPS) and X‐ray diffraction (XRD) analyses were able to confirm the oxidation states and formation of the prepared QDs. UV/Vis was capable of finding the optical band gap energy and the photostability of the QDs. The resultant Ga2Te3 QDs together with metal ions confirmed their use for DNA signal detection through their DNA binding mechanism in the genosensor construction. Genosensing in Cs+ and Li+ ions exhibited high sensitivity (2.74–3.69 μA ng−1 mL) and very low detection limits (0.4 pg mL−1) with a linear dynamic range of 0.1–1 ng mL−1.