Ga Deposition Research Articles

Study on electrodeposition of gallium-selenium binary alloy films from Deep Eutectic Solvent

Ga-Se alloy coatings were successfully electrodeposited at different deposition potentials from Deep Eutectic Solvent (choline chloride-ethylene glycol). The co-deposition mechanism of Ga and Se was investigated through cyclic voltammetry (CV) and chronoamperometry (CA). The results indicate that the co-deposition of Ga and Se occurs through an induced co-deposition mechanism, with Se deposition taking place initially, followed by the induced deposition of Ga. Furthermore, the Ga-Se co-deposition process was analyzed with the Scharifker-Hills model. The research results indicate that with the negative shift of the deposition potential, the Ga-Se co-deposition process gradually transitions from diffusion-controlled three-dimensional progressive nucleation and growth to three-dimensional instantaneous nucleation and growth.Characterization of the surface morphology and composition of the obtained coatings at different potentials was analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results reveal that with the negative shift of the deposition potential, the morphology of the coating transforms from spherical to granular, and as the deposition potential continues to decrease, the granules further refine. Simultaneously, with the negative shift of the deposition potential, the relative content of Ga in the coating increases, while the relative content of Se decreases. The Ga-Se alloy coatings before and after annealing were characterized by X-ray diffraction spectroscopy (XRD). The results indicate that, after annealing, the coating exhibits the phase of GaSe. Besides, the optical and electrical properties of the annealed Ga-Se alloy coating were investigated by UV–visible spectroscopy and photoelectrochemical techniques. The results demonstrate that the coating exhibits excellent optical and electrical characteristics, with a photocurrent response of 0.014 mA/cm2, a bandgap of 1.98 eV, and p-type conductivity.

Monte Carlo simulation of planar GaAs nanowire growth

The Monte Carlo model for the planar GaAs nanowire growth via the vapor–liquid-solid mechanism on GaAs substrate using a gallium droplet as a catalyst is realized. The effect of temperature, Ga and As2 deposition rates, substrate orientation and surface properties on the morphology of planar GaAs nanowires is considered. It is shown, that at the initial stages of nanowire growth, a 3D GaAs crystal is formed under a gallium droplet, which sets the nanowire growth direction. The range of temperatures and deposition rates of gallium and arsenic, which ensure the planar nanowire formation on the GaAs(111)A surface, is determined. The investigation of surface properties influence on the nanowire morphology showed that the arsenic diffusion influx into a gallium droplet is of critical importance for the planar GaAs nanowire growth. Ways for achieving a unidirectional growth of planar nanowires on singular and vicinal GaAs surfaces are proposed.

Demonstration of MOCVD based in situ etching of β-Ga2O3 using TEGa

In this work, we demonstrate an in situ etch technique for β-Ga2O3 inside a metalorganic chemical vapor deposition (MOCVD) reactor using triethylgallium (TEGa) as the etching agent. At sufficiently high substrate temperatures (Tsub), TEGa is introduced into the MOCVD reactor which undergoes pyrolysis, resulting in the deposition of Ga on the β-Ga2O3 surface. These Ga adatoms react with Ga2O3 to form gallium suboxide (Ga2O), which desorbs from the β-Ga2O3 surface resulting in the etching of the epilayer. MOCVD chamber parameters such as TEGa molar flow rate, substrate temperature, and chamber pressure were shown to be key in controlling the etch rate and surface morphology. A wide range of etch rates from ∼0.3 to 8.5 μm/h is demonstrated by varying the etch parameters. In addition, smooth surface morphology on (010) and (001) β-Ga2O3 substrates is also demonstrated. This new etch technique could enable damage free fabrication of 3D structures like fins and trenches, which are key components in many β-Ga2O3 device structures.

The production of high-purity gallium from waste LEDs by combining sulfuric acid digestion, cation-exchange and electrowinning

White light beads containing light emitting diodes (LED) were removed from the commercial light bulbs and treated with a complex, but easily implementable hydro-electrometallurgical method to recover pure Ga. Using concentrated H2SO4 as the digesting agent at 180 °C for 60 min resulted in > 90% efficiencies of gallium and indium solubilization by the subsequent water leaching. All metals - except for Ag – could be fixed in a strongly acidic cation-exchange resin by loading the solution into a chromatographic column. Indium, Cd, Pb and Sn are selectively eluted with 1 M HCl, while Al can be transferred into the aqueous phase using a 0.25 M NaF solution. Gallium is recovered in a pure eluate from the resin with 3 M NaOH, and finally, Y is eluted with 0.5 M Na2CO3. The cathodic deposition of Ga from the alkaline eluate was studied by potentiodynamic and galvanostatic methods. As high current efficiencies as 99% could be reached in solutions of 50 g/dm3 Ga and 6 M free NaOH at 300 A/m2 cathodic current density. Decreasing the NaOH concentration to 1.5 M resulted in a 10 ∼ 15% decrease in the current efficiency. Lower Ga concentrations also reduced the current efficiency significantly. The cell voltages were in the range of 2.1–2.4 V, yielding a relatively low (2 kWh/kg) specific energy consumption. The obtained cathodes were immersed into 2 M HCl at 55 °C, resulting in 99.999% Ga metal melted from Ti mother plates.

Modeling of Masked Droplet Deposition for Site-Controlled Ga Droplets.

Site-controlled Ga droplets on AlGaAs substrates are fabricated using area-selective deposition of Ga through apertures in a mask during molecular beam epitaxy (MBE). The Ga droplets can be crystallized into GaAs quantum dots using a crystallization step under As flux. In order to model the complex process, including the masked deposition of the droplets and a reduction of their number during a thermal annealing step, a multiscale kinetic Monte Carlo (mkMC) simulation of self-assembled Ga droplet formation on AlGaAs is expanded for area-selective deposition. The simulation has only two free model parameters: the activation energy for surface diffusion and the activation energy for thermal escape of adatoms from a droplet. Simulated droplet numbers within the opening of the aperture agree quantitatively with the experimental results down to the perfect site-control, with one droplet per aperture. However, the model parameters are different compared to those of the self-assembled droplet growth. We attribute this to the presence of the mask in close proximity to the surface, which modifies the local process temperature and the As background. This approach also explains the dependence of the model parameters on the size of the aperture.

Co-achievement of enhanced absorption and elongated retention of insoluble drug in lungs for inhalation therapy of pulmonary fibrosis

The unique composite particles consisting of γ-cyclodextrin metal-organic framework (MOF) (0.5–3 μm of geometric particle size) and 18 β-Glycyrrhetinic acid (GA) were developed as dry powder inhaler (DPI) to alleviate idiopathic lung fibrosis (IPF), which possessed the property of biphasic release in vivo and vitro. In vitro release, the burst release of almost 55% emerged before 2 min and the continued release maintained till 120 h. This specifical phenomenon might be attributed to the structure of MOF containing a pair of γ-CD and cavity. Compared to GA raw material group, the AUC0-t and Cmax of GA@MOF inhalation were enhanced about 3.8 times and 21.4 times, respectively. Furthermore, the absorption time prolonged by 8 h which elongated retention of GA in lungs. Evident by the 92% deposition of GA in the lung based on its biodistribution result, it made sense to expect a locally direct effect on IPF via inhalation

Influence of laser absorption by water- and gas-atomised powder feedstock on Laser Metal Deposition of AISI 431 stainless steel

This research explores the importance of the powder feedstock characteristics on the manufacturing of martensitic stainless steel elements by Laser Metal Deposition (LMD). Water- and gas-atomised (WA and GA respectively) powders are the most common feedstock material used in LMD. The atomisation process medium influences powder properties including particle size distribution, inner and outer morphology, and microstructure. In this work, commercial WA and GA powders of AISI 431 stainless steel alloy were used to produce LMD coatings under identical deposition parameters. It was found that the powder processing route significantly affected the powder’s morphology, and this led to large changes in the laser energy absorbance during LMD. Consequently, significant changes in the microstructure of the deposited layer were observed. The parts manufactured with WA powder presented a duplex structure composed of martensite and ferrite, while a predominantly martensitic structure was verified in the GA deposition. The microstructural differences led to a wear rate reduction by a factor of 35 and a gain of 150 mV in pitting potential in the GA material. Though, the application of GA powder increased the production cost by 53% due to its lower deposition efficiency and higher retail price. The marked differences have all been attributed to the characteristics of the starting powder feedstock. This work highlights that the properties of the powder feedstock are a critical parameter in determining the properties of the LMD material, and emphasises the importance of the powder processing route on the energy absorption during LMD. • Water-atomised powder absorbs more laser energy compared to gas-atomised powder. • Higher laser energy absorbance resulted in a duplex microstructure for the water-atomised AISI 431 stainless steel. • Lower laser energy absorbance resulted in a fine martensitic microstructure with improved wear and corrosion performance for the gas-atomised AISI 431 stainless steel.

Liquid deposition modification of nano-ZSM-5 zeolite and catalytic performance in aromatization of Hexene-1

The Olefin aromatization is an important method for the upgrade of catalytic cracking (FCC) gasoline and production of fuel oil with high octane number. The nano-ZSM-5 zeolite was synthesized via a seed-induced method, a series of modified nano-ZSM-5 zeolite samples with different Ga deposition amount were prepared by Ga liquid deposition method. The XRD, N2 physical adsorption, SEM, TEM, XPS, H2-TPR and Py-IR measurements were used to characterize the morphology, textural properties and acidity of the modified ZSM-5 zeolites. The catalytic performance of the Hexene-1 aromatization was evaluated on a fixed-bed microreactor. The effects of Ga modification on the physicochemical and catalytic performance of nano-ZSM-5 zeolites were investigated. The Ga species in the modified nano-ZSM-5 zeolites mainly exist as the form of Ga2O3 and GaO+, which provide strong Lewis acid sites. The aromatics selectivity over Ga modified nano-ZSM-5 zeolite in the Hexene-1 aromatization was significantly increased, which could be attributed to the improvement of the dehydrogenation activity. The selectivity for aromatics over the Ga4.2/NZ5 catalyst with suitable Ga deposition amount reached 55.4%.

Improving the yield of GaAs nanowires on silicon by Ga pre-deposition

GaAs nanowire (NW) arrays were grown by molecular beam epitaxy using the self-assisted vapor−liquid−solid method with Ga droplets as seed particles. A Ga pre-deposition step is examined to control NW yield and diameter. The NW yield can be increased with suitable duration of a Ga pre-deposition step but is highly dependent on oxide hole diameter and surface conditions. The NW diameter was determined by vapor-solid growth on the NW sidewalls, rather than Ga pre-deposition. The maximum NW yield with a Ga pre-deposition step was very close to 100%, established at shorter Ga deposition durations and for larger holes. This trend was explained within a model where maximum yield is obtained when the Ga droplet volume approximately equals the hole volume.

Ge-GaN deposition: An assistant kMC model

The present work provides a parametric simulation tool to assist the experimental deposition of GaN and Ge-GaN material. For this purpose, a kinetic Monte Carlo (kMC) model was developed and implemented to simulate the deposition, diffusion, and desorption of Ge, Ga, and N and subsequent material growth on GaN (0001). The kMC is a Monte Carlo algorithm that simulates the dynamics of a given on-the-lattice system by computing on-the-fly every event rate. In the present model, the deposition rates were computed by means of the collision theory and the diffusion and desorption rates were calculated with the usual Arrhenius form based on knowledge of the activation energies and the local energy configuration. Ge diffusion energies as well as experimental deposition conditions were simulated to investigate their impact on the resulting Ge-GaN layers. Proposed kMC model outcomes, which are consistent with the observed experimental results, are discussed in detail and conclusions are provided.

Kinetic calculation analysis of Ga deposition on the morphology evolution of GaAs quantum ring

GaAs Quantum Ring (QR) was gained on GaAs (001) by Droplet Epitaxy (DE), and the microscopic morphology of the GaAs samples was observed by Scanning Tunnel Microscope (STM). The kinetic model of Local Droplet Etching (LDE) was mainly used to study the influence of Ga deposition on the morphology evolution from Ga droplets to GaAs QR. Comparing experimental data with the theoretical value, it can be seen that the increase of Ga deposition will cause the reduction of surface density of Ga droplets, but the volume, height and diameter of Ga droplets will increase. Geometric dimension of GaAs QR increased also with the increase of Ga deposition. In addition, it found that the rate at which the substrate was etched was affected by Ga deposition and As pressure from experiment. The more Ga deposition, the deeper GaAs nano hole. However, GaAs nano hole became shallower under high As pressure. These results are consistent with theoretical calculation analysis. Under high substrate temperature, GaAs double rings finally evolved into a single ring. Above all results have certain guiding significance for the preparation of patterned GaAs substrates and the controlled growth of GaAs QR morphology.

Carbonates at the supergiant Olypmic Dam Cu-U-Au-Ag deposit, South Australia part 2: Sm-Nd, Lu-Hf and Sr-Pb isotope constraints on the chronology of carbonate deposition

Mineralization at the supergiant Cu-U-Au-Ag Olympic Dam deposit (South Australia), the ‘uranium endmember’ of the iron-oxide copper–gold (IOCG) spectrum of ore deposits, is hosted in a breccia complex developed entirely within granite of the 1.59 Ga Hiltaba Suite (Gawler Craton). Earlier studies suggested brecciation and mineralization occurred within a magmatically-driven hydrothermal system at 1.59 Ga, with a critical role for mafic–ultramafic intrusions. In contrast, recent radiometric dating of the breccia complex indicates a prolonged, multi-stage history of brecciation and mineralization from 1.59 to 0.5–0.4 Ga. Ca-Fe-Mg-Mn-carbonate gangue minerals are associated with ore minerals at virtually every stage of mineralization. In a companion study (Apukhtina et al., 2020), this mineralogically, texturally and compositionally diverse carbonate mineral suite was assigned to seven associations defined on the basis of host lithology and texture. Here we report Sm-Nd, Pb-Pb and Lu-Hf isotope ages for these carbonates, which are used to examine the chronology of carbonate deposition. Initial Sr-Nd isotopic compositions are used to place constraints on fluid sources. Sm-Nd and Pb-Pb isotope systematics of calcite veins in ~1.59 Ga IOCG ore indicate 1.59–1.55 Ga deposition ages. Likewise, locally abundant laminated siderites have Sm-Nd ages in this age interval. A world-first attempt to apply Lu-Hf dating to carbonate gangue in an ore deposit yields ages that are 70–100 Ma younger than corresponding Sm-Nd ages, presumably reflecting isotopic exchange of carbonate Lu-Hf isotope systems with host rocks. Sm-Nd ages for carbonates assigned to other carbonate associations (hosted in highly altered inferred 1.59 Ga basalt and picrite; diverse settings within granite-dominated breccia; locally abundant megaclasts of green and red bedded sandstone/mudstone sequences; ~0.82 Ga doleritic dykes) are more diverse and range from ~1.59 to 0.5 Ga. The structurally youngest carbonates (unbrecciated fluorite-barite veins; carbonate matrix in polymict conglomerate above the breccia complex) yield ~0.50 Ga Sm-Nd ages. Inferred carbonate ages are broadly consistent with radiometric dates for other hydrothermal minerals (e.g., hematite, uraninite, apatite, fluorite). They suggest that mineralization initiated at 1.59 Ga was reworked and possibly increased in size in response to large-scale tectonic, magmatic, sedimentary and hydrothermal events. Initial 87Sr/86Sr in the carbonates is higher and more variable (0.710–0.752, average ~0.721) than could be explained by ore and gangue mineral formation from magmatic-hydrothermal fluids during a single event at 1.59 Ga, a model favored in several earlier studies. By contrast, carbonate formation over a long period, as inferred from the Sm-Nd chronology presented here, would allow ingrowth of 87Sr in the granitic host rocks to develop the heterogeneous initial 87Sr/86Sr recorded in the carbonates. Carbonate-bearing fluids appear to have sourced Nd (and most likely also Sr) locally, within the host granite and breccia, with contributions from mafic rocks. The emerging evidence for protracted, multi-stage mineralization implies that single-stage models for Olympic Dam need to be revisited and that all studies of sulfide and gangue minerals in this deposit require careful radiometric dating. We speculate that the polymetallic nature and unusually large metal reserves of the Olympic Dam mineralization are related to its multi-stage formation history.

Ga2Se3 Nanowires via Au-Assisted Heterovalent Exchange Reaction on GaAs

Out-of-plane Ga2Se3 nanowires are grown by molecular beam epitaxy via Au-assisted heterovalent exchange reaction on GaAs substrates in the absence of Ga deposition. It is shown that at a suitable t...

Pt–Ga Model SCALMS on Modified HOPG: Thermal Behavior and Stability in UHV and under Near-Ambient Conditions

We have prepared model systems for Pt–Ga supported catalytically active liquid metal solutions (SCALMS) by physical vapor deposition of Pt and Ga onto highly oriented pyrolytic graphite (HOPG). Pri...

Size tunable Ga–Ge nanowires for Li-ion battery prepared by in situ alloying in ionic liquid electrodeposition

Germanium (Ge)-based materials have become important candidates for high-performance Li ion battery applications; however, the cycling performance and rate capability require further improvement to meet the fast development of mobile devices. Ge-based alloy nanowires provide a high surface to volume ratio as well as optimal alloy materials, both of which are advantageous for obtaining high-performance Li ion battery anodes. In this paper, we report in situ Ga–Ge alloying in ionic liquid electrodeposition to prepare size tunable Ga–Ge nanowires. The size of the seed Ga particles increases with solution temperature, thus leading to increasing diameter and length of the Ga–Ge nanowires. The smallest diameter nanowires grown at a Ga deposition temperature of 25 °C yield the best cycling performance (1101 mA h g−1 after 100 cycles at 0.32 A g−1) and rate capability (728 mA h g−1 at 16 A g−1) among all four tested samples.

Atomic layer deposition and annealing of Ga doped ZnO films

Ga doped ZnO films were deposited at low temperature with atomic layer deposition at different temperatures with the novel precursor, hexakis (dimethylamino)gallium. The ZnO films prepared at 300 °C on GaN substrates are epitaxial, but the Ga doping deteriorates the crystallinity: the doped films are oriented polycrystalline. The films deposited at lower temperatures are polycrystalline in all cases. Post deposition annealing procedures were applied which improved the crystallinity of the layer and increased the mobility of the films.

Pt–Ga Model SCALMS on Modified HOPG: Growth and Adsorption Properties

Single atom catalysts hold a great potential in heterogeneous catalysis. In this model study, we report on the observation of Pt single atoms in low-melting-point Pt–Ga alloy prepared on modified highly oriented pyrolytic graphite (HOPG) under ultrahigh vacuum (UHV) conditions. In the first part, we examined the growth of Pt nanoparticles (NP) on HOPG modified by Ar+ bombardment. In the second part, we used physical vapor co-deposition of Pt and Ga to prepare model systems for supported catalytically active liquid metal solutions. We employed infrared reflection absorption spectroscopy with CO as a probe molecule and atomic force microscopy to study the growth and adsorption properties of Pt–Ga aggregates in comparison to Pt NPs. The presence of CO during Pt deposition leads to formation of ordered Pt particles mainly exposing terrace sites. On Pt–Ga nanoalloys, CO induces Pt segregation to the surface. In contrast, Ga deposition onto Pt in UHV or evaporation of small amounts of Pt onto Ga results in the formation of isolated Pt atoms on the surface of the alloy. Comparing alloys with different Pt concentrations, we show that the coordination environment around Pt influences the binding energy of the adsorbed CO.

Pd-Ga model SCALMS: Characterization and stability of Pd single atom sites

We have prepared model systems for Pd-Ga supported catalytically active liquid metal solutions (SCALMS) by physical vapor deposition of Pd and Ga in ultrahigh vacuum onto highly oriented pyrolytic graphite (HOPG) pre-modified by Ar+ bombardment. Combining AFM and IRAS with CO as a probe molecule, we investigate the growth behavior, the morphology, the surface chemistry, and the stability of Pd-Ga alloys on HOPG.Our results prove the single atom character of the active sites in Ga-rich Pd-Ga alloys. We show that upon interaction with CO, Ga is displaced from the surface and CO adsorbs in on-top position on surface Pd atoms. Experimental data on the vibrational frequencies and binding energies of CO are compared to the results of DFT calculations for CO adsorption on four different Pd-Ga models, i.e. PdGa(1 0 0), PdGa(1¯1¯1¯), Pd-doped α-Ga(0 0 1), and Pd-doped fcc-Ga(1 0 0). The comparison suggests that widely separated Pd sites are formed in the Ga matrix.

Pulsed laser deposition of Ga doped ZnO films - Influence of deposition temperature and laser pulse frequency on structural, optical and electrical properties

The contribution deals with Ga doped ZnO films (deposited from a sintered target composed of 99.0 ZnO and 1.0 wt % of Ga2O3) prepared by pulsed laser deposition (PLD). Experimentally were compared the deposition parameters influence on structural, optical and electrical properties. The variable parameters were: deposition temperature (RT to 500 °C) and growth rate (controlled by laser pulsing repetition frequency in range 2–50 Hz). Investigation by SEM and XRD confirmed columnar structure of prepared films with highly uniform crystallographic orientation regardless of applied deposition parameters. Samples exhibited high optical transparency in VIS region with sharp absorption edge near 380 nm and band gap energies varied between 3.19 and 3.24 eV at room temperature. The best electrical properties (resistivity ∼5.96 × 10−4 Ω cm) was achieved at 400 °C and 10 Hz of laser frequency, however the application of deposition at RT or highest laser frequency (50 Hz) still maintain average resistivity at levels of 10−3 Ω cm. The results suggest that PLD can play an important role in production of high conductive transparent thin film deposited on temperature sensitive organic materials at RT deposition levels.

Control of the structure and photoelectrical properties of Cu(InGa)Se2 film by Ga deposition potential in two-step electrodeposition

In present work, a simple two-step electrodeposition method (first CuIn then Ga) was used to prepare the Cu-In-Ga precursor. The as-deposited films were selenized in nitrogen atmosphere at 550 °C for 40 min. The effect of Ga deposition potential on the structural, morphological, optical and electrical properties were investigated by means of X-ray diffraction, Raman spectra, scanning electron microscopy, UV–visible Spectroscopy and photo-electrochemical measurement, respectively. XRD results show that prepared Cu(InGa)Se2 films have a tetragonal chalcopyrite CIS with preferential orientation along the (112) orientation. And the size of grain and the band gap were various with the increase of the Ga deposited potential, resulting in the effective control of photo-current intensity of Cu(InGa)Se2. The Mott–Schottky plots confirmed all the films exhibited a good p-type semiconductor characteristic.