Amorphous Oxide Films Research Articles

Ion-gating analysis on conduction mechanisms in oxide semiconductors

• Self-gated field-effect by ion adsorption at the solid–liquid interface (ion-gating). • Resistive factors of indium tin oxide controlled depending on sputtering conditions. • A fundamental correlation between the ion-gating effect and the resistive factors. • Ion-gating analysis on the resistance-dependent behavior of electrons in the electrode. • Identification of conduction mechanisms in amorphous oxide semiconductors. The electric field-effect is one of the common methods to tune the conductivity of materials in semiconductor devices because it can control the accumulation or depletion of charge carriers. However, to efficaciously dominate the electrical properties of the semiconductor in such a way, the application of an external voltage through the gate is an inevitable condition. Here, we propose an ion-dynamics-driven (ionovoltaic) transducer focusing on a self-gated field-effect by ion adsorption at the solid–liquid interface (an ion-gating effect without applied electric field). Considering an effective resistance derived from the generated signal, we establish an equivalent circuit of the ion-gating field-effect transducer to specifically analyze the conduction behavior of traveling electrons in an amorphous indium tin oxide film. As a result, using water droplet flow, we provide a convenient method to identify inherent conduction mechanisms of amorphous oxide semiconductors. This analysis has great potential as a tool to leap forward into a new interdisciplinary approach covering interface science and solid-state physics from a peculiar concept based on the ion-gating effect.

Transformation of amorphous passive oxide film on Zr65Cu17.5Ni10Al7.5 metallic glass ribbons

Zr-based metallic glass with favorable properties and a stable surface oxide layer is foreseen as an alternative material for water/nuclear reactor pressure systems. The high stability of Zr65Cu17.5Ni10Al7.5 metallic glass (MG) in anodic and cathodic regions within 0.5 M H2SO4 solution is evidenced by the negligible shift in the corrosion potential upon linear sweep voltammetry cycles. The recorded passivation current density of 15 mA cm–2 is very similar to 430 stainless steel. The formation of an amorphous Zr-rich oxide phase and slight dissolution of the native ZrO2 layer are confirmed by scanning transmission electron microscopy – energy dispersive X-ray analysis, which result from the interaction of hydronium ions (H3O+) with the oxide layer during linear polarization. Furthermore, promising hydrogen absorption of the produced Zr-based MG ribbons (1.33 %wt, non-reversible) by Sieverts-type apparatus were recorded at 400 °C and under 6 MPa, which evidences that this alloy can minimize the hydrogen evolution within the chamber due to the coverage with an oxide film and thereby prevent accidents.

Preliminary study of the photodegradation of dyes using amorphous films of ZnO-CuO obtained by photochemical deposition in solid phase.

Here, we propose an original method of photochemical deposition for the synthesis of metal oxides from coordination complexes sensitive to UV light. The method consists of the synthesis of zinc oxide amorphous films doped with different concentrations of copper oxide followed by annealing at 600°C. The photo-reactivity of the samples was evaluated by the decrease of the FT-IR spectroscopy bands. The films were analyzed by scanning electron microscopy (SEM-EDX) and X-ray diffraction (XRD) to study their morphology and structures, respectively. The results show an amorphous characteristic in the photo-deposits. The optical properties show a gradual decrease of both the optical band gap and the luminescent emissions of the ZnO photo-deposits when CuO doping increases. Both properties allow a shift in absorption towards the visible and a decrease in the rate of recombination of charge carriers. The photocatalytic activity was analyzed using methyl orange and methylene blue as pollutants under a lamp that emulates solar energy. The results show that the photocatalytic activity is favored by the insertion of CuO; 46.6 and 93.0% efficiency in the photodegradation of methyl orange and methylene blue, respectively, were reached at 1.0mol % of CuO with respect to pure ZnO. These differences in degradation efficiency respond to the chemical stability of the dyes. Finally, the use of appropriate scavengers suggests an oxidative route in the dye degradation mechanism.

Highly flexible deep-ultraviolet photodetectors using amorphous gallium oxide thin films grown by atomic layer deposition

Flexible deep ultraviolet (DUV) photodetectors have increased applicability in healthcare and electronic skin, however, sufficient flexibility of DUV photodetectors has not yet been achieved. In this study, we developed highly flexible DUV photodetectors using amorphous gallium oxide (GaOx) films grown by atomic layer deposition, which enabled a bending radius as small as 1.5 mm. The high flexibility originated from a residual compressive strain in the GaOx films and the amorphous nature of the thin GaOx films (~ 25 nm) grown on polyimide substrates. Therefore, the high flexibility of DUV photodetectors can provide a promising opportunity in healthcare systems, e-skins, and wearable applications.

Polymer-assisted deposition and room-temperature ferromagnetism of amorphous Mn-doped gallium oxide films

In this work, amorphous Mn-doped gallium oxide (a-GMO) films are prepared by polymer-assisted deposition. The a-GMO films exhibit room-temperature ferromagnetism (RTFM) and their saturation magnetization (MS) and coercive field (HC) values are dependent on the Mn concentration. Interestingly, a lower Mn-doping concentration (3.1%) is sufficient to trigger the RTFM in the a-GMO films, in comparison with the previously-reported values in crystalline Mn-doped β-Ga2O3 (11%) and γ-Ga2O3 (7.0%). Furthermore, the a-GMO films exhibit higher MS values than those crystalline Mn-doped Ga2O3 films at the medium doping levels between 10% and 20%. Further analysis shows that the enhancement of the ferromagnetism comes from the strong coupling between abundant oxygen vacancies (VOs) and Mn ions in the a-GMO films. Our results give insight to the RTFM of the a-GMO films and may be useful for the design, fabrication and application of spintronic materials based on gallium oxide.

Inherent selective pulsed chemical vapor deposition of amorphous hafnium oxide / titanium oxide nanolaminates

Water-free Inherent selective pulsed chemical vapor deposition (CVD) of HfO2/TiO2 nanolaminates on Si and SiO2 in preference to SiCOH has been studied. SiCOH is highly porous alkylated SiO2, which is used as a nonreactive low-k dielectric. Ti(OiPr)4 [titanium(IV) isopropoxide] and Hf(OtBu)4 [Hafnium tert butoxide] were used in the CVD study. Previous studies showed that metal alkoxide precursors could form oxide films through thermal decomposition. However, single oxide films greater than 2 nm can be rough due to crystallization. To solve this issue, HfO2/TiO2 nanolaminate structures were studied. With sequential dosing of each precursor in a supercycle at 300 °C sample temperature, HfO2/TiO2 nanolaminate films with thin (less than 3 nm) sublayers were selectively deposited. The films were smooth with root mean square (RMS) roughness lower than 0.5 nm and almost amorphous from XRD analysis; this is unexpected since both oxides readily crystalize. Amorphous nanolaminate oxide film deposition with high selectivity was achieved by controlling each sublayer thickness and the Hf:Ti ratio. TEM studies proved that ∼ 20 nm of the nanolaminate film could also be selectively deposited on nanoscale patterned surfaces. This selective amorphous nanolaminate oxide CVD process has a potential to be applicable in the nanoscale patterning in MOSFET fabrication.

Oxygen annealing induced crystallization and cracking of pulsed laser deposited Ga2O3 films

Amorphous gallium oxide (Ga 2 O 3 ) films had been prepared on c-sapphire substrate through utilizing pulsed laser deposition at 400 °C and then annealed at various temperatures in an oxygen circumstance. The influence of annealing temperature from 500 to 1000 °C on texture, optical characters, chemical valence state, and surface topography of Ga 2 O 3 films was elaborated systematically. The amorphous film begins to crystallize at 500 °C and the crystallization has been continuously enhanced with the increasing annealing temperature. The optimization annealing temperature is obtained at 700 °C for Ga 2 O 3 thin films with the ratio of 90.4% Ga 3+ valence state and 88.6% lattice oxygen which owns a relatively good crystal quality and flat-continuous surface. However, when the temperature goes up to 800 °C and above, some cracks appeared in the film, which could be contributed to the high temperature enhanced Al diffusion into the film as well as the thermal expansion coefficient mismatch between the Ga 2 O 3 films and substrate. The efforts were directed to understand the annealing behavior and thus to derive enhanced ability for manipulation with the specific crystal structure and phase while optimizing the conditions to obtain desirable properties for the integration of Ga2O3 films in electronic device applications. • The influence of annealing temperature in a wide range from 500 to 1000 °C on the properties of pulsed laser deposited amorphous Ga2O3 film at 400 °C on sapphire substrate was elaborated systematically. • Two kinds of annealing mechanisms were clarified in different temperature range, namely thermal enhanced crystallization (≤700 °C) and high temperature enhanced Al diffusion (800 °C–1000 °C). • Some cracks appeared in the film after high temperature annealing, which could be mostly contributed to the high temperature enhanced Al diffusion into the film. • The optimization annealing temperature is obtained at 700 °C for Ga 2 O 3 thin films with the ratio of 90.4% Ga 3+ valence state and 88.6% lattice oxygen which owns a relatively good crystal quality and flat-continuous surface.

Hot-Pressed Two-Dimensional Amorphous Metals and Their Electronic Properties

As an emerging research field, two-dimensional (2D) metals have been the subject of increasing research efforts in recent years due to their potential applications. However, unlike typical 2D layered materials, such as graphene, which can be exfoliated from their bulk parent compounds, it is hardly possible to produce 2D metals through exfoliation techniques due to the absence of Van der Waals gaps. Indeed, the lack of effective material preparation methods severely limits the development of this research field. Here, we report a PDMS-assisted hot-pressing method in glovebox to obtain ultraflat nanometer-thick 2D metals/metal oxide amorphous films of various low-melting-point metals and alloys, e.g., gallium (Ga), indium (In), tin (Sn), and Ga0.87Ag0.13 alloy. The valence states extracted from X-ray photoelectron spectroscopy (XPS) indicate that the ratios of oxidation to metal in our 2D films vary among metals. The temperature-dependent electronic measurements show that the transport behavior of 2D metal/metal oxide films conform with the 2D Mott’s variable range hopping (VRH) model. Our experiments provide a feasible and effective approach to obtain various 2D metals.

A Transparent Semiconducting Surface for Capturing and Releasing Single Cells from a Complex Cell Mixture.

Selective isolation of individual target cells from a heterogeneous population is technically challenging; however, the ability to retrieve single cells can have high significance in various aspects of biological research. Here, we present a new photoelectrochemical surface based on a transparent electrode that is compatible with high-resolution fluorescence microscopy for isolating individual rare cells from complex biological samples. This is underpinned by two important factors: (i) careful design of the electrode by patterning discrete Au disks of micron dimension on amorphous silicon-indium tin oxide films and (ii) orthogonal surface chemistry, which modifies the patterned electrode with self-assembly layers of different functionalities, to selectively capture target cells on the Au disks and resist cell binding to the amorphous silicon surface. The co-stimulation of the surface using light from a microscope and an electric potential triggers the reductive desorption of the alkanethiol monolayer from the Au disks to release the single cells of interest from the illuminated regions only. Using circulating tumor cells as a model, we demonstrate the capture of cancer cells on an antibody-coated surface and selective release of single cancer cells with low expression of epithelial cell adhesion molecules.

12.42% Monolithic 25.42 cm2 Flexible Organic Solar Cells Enabled by an Amorphous ITO-Modified Metal Grid Electrode.

Printed metal nanogrid electrode exhibits superior characteristics for use in flexible organic solar cells (OSCs). However, the high surface roughness and inhomogeneity between grid and blank region is adverse for performance improvement. In this work, a thin amorphous indium tin oxide (ITO) film (α-ITO) is introduced to fill the blank and to improve the charge transporting. The introduction of α-ITO significantly improves the comprehensive properties of metal grid electrode, which exhibits excellent bending resistance and long-term stability under double 85 condition (under 85°C and 85% relative humidity) for 200 h. Both experimental and simulation results reveal α-ITO with a sheet resistance of 20 000 Ω □-1 is sufficient to improve the charge transporting within the adjacent grids, leading to a remarkable efficiency of 16.54% for 1 cm2 flexible devices. With area increased to 4.00, 9.00, and 25.42 cm2 , the devices still display a performance of 16.22%, 14.69%, and 12.42%, respectively, showing less efficiency loss during upscaling. And the 25.42 cm2 monolithic flexible device exhibits a certificated efficiency of 12.03%. Moreover, the device shows significantly improved air stability relative to conventional high-conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate-modified device. All these make the α-ITO-modified Ag/Cu electrode promise to achieve high-efficient and long-term stable large-area flexible OSCs.

Water-assisted crystallization of amorphous indium zinc oxide films

Transparent conductive materials based on indium oxide remain yet irreplaceable in various optoelectronic applications. Amorphous oxides appear especially attractive for technology as they are isotropic, demonstrate relatively high electron mobility and can be processed at low temperatures. Among them is indium zinc oxide (IZO) with a large zinc content that is crucial for keeping the amorphous state but redundant for the doping. In this work we investigated water-free and water containing IZO films obtained by radio frequency sputtering. The correlation between temperature driven changes of the chemical state, the optical and electrical properties as well as the progression of crystallization was in focus. Such characterization methods as: scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, temperature dependent Hall-effect measurements and others were applied. Temperature dependent electrical properties of amorphous IZO and IZO:H2O films were found to evolve similarly. Based on our experience in In2O3:H2O (In2O3:H or IOH) we proposed an explanation for the changes observed. Water admixture was found to decrease crystallization temperature of IZO significantly from ∼ 550 °C to ∼ 280 °C. Herewith, the presence and concentration of water and/or hydroxyls was found to determine Zn distribution in the film. In particular, Zn enrichment was detected at the film’s surface respective to the high water and/or hydroxyl amount. Raman spectra revealed a two-dimensional crystallization of w-ZnO which precedes regardless water presence an extensive In2O3 crystallization. An abrupt loss of electron mobility as a result of crystallization was attributed to the formation of ZnO interlayer on grain boundaries.

Understanding methanol dissociative adsorption and oxidation on amorphous oxide films.

Interactions between a transition metal (oxide) catalyst and a support can tailor the number and nature of active sites, for instance in the methanol oxidation reaction. We here use ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify and compare the surface adsorbates that form on amorphous metal oxide films that maximize such interactions. Considering Al(1-x)MxOy (M = Fe or Mn) films at a range of methanol : oxygen gas ratios and temperatures, we find that the redox-active transition metal site (characterized by methoxy formation) dominates dissociative methanol adsorption, while basic oxygen sites (characterized by carbonate formation) play a lesser role. Product detection, however, indicates complete oxidation to carbon dioxide and water with partial oxidation products (dimethyl ether) comprising a minor species. Comparing the intensity of methoxy and hydroxyl features at a fixed XPS chemical shift suggests methanol deprotonation during adsorption in oxygen rich conditions for high transition metal content. However, increasing methanol partial pressure and lower metal site density may promote oxygen vacancy formation and the dehydroxylation pathway, supported by a nominal reduction in the oxidation state of iron sites. These findings illustrate that AP-XPS and mass spectrometry together are powerful tools in understanding metal-support interactions, quantifying and probing the nature of catalytic active sites, and considering the link between electronic structure of materials and their catalytic activity.

Changes in the titanium oxide optical properties during crystallization

Crystallization of amorphous titanium oxide films synthesized by magnetron sputtering was carried out at temperatures of 700, 800, and 900oC in an oxygen atmosphere. The refractive index of the films increases during crystallization with a time constant that depends on temperature, which made it possible to determine the activation energy of the crystallization process on the order of 0.6 eV. The growth kinetics model for the titanium oxide nanocrystals, which is used in this work, showed that the indicated activation energy corresponds to the diffusion energy of oxygen vacancies. This process is decisive for the growth of titanium oxide nanocrystals upon annealing in an oxygen atmosphere. The study of photoluminescence has shown that crystallization leads to a change in the ratio of intensities of different emission bands. The bands that are associated with the oxygen vacancy are extinguished. A decrease in the concentration of these vacancies in films leads to an increase in their resistance and stabilization of the films in time. Keywords: titanium oxide films, crystallization, refractive index, photoluminescence.

Coloring and Bleaching Properties of 500–1000 nm‐Thick Electrochromic Tungsten Oxide Films Deposited by Reactive Direct Current Magnetron Sputtering

Amorphous tungsten oxide films are prepared on indium tin oxide/glass substrates using reactive magnetron sputtering and their electrochromic (EC) properties are investigated. To achieve the densely colored films, samples of 500 and 1000 nm thickness are deposited with different pumping speeds and oxygen flow rates at Ar 3 Pa atmosphere. The as‐deposited films are similarly transparent (≈80%), but their EC properties vary depending on the deposition conditions and strongly on film thickness. The 500 nm‐thick samples have a transmittance of 4–8% in the colored state, which recover well in the bleached state. In contrast, the 1000 nm‐thick films have very low transmittance (<1%) in the colored state but are not completely recovered. Among 1000 nm‐thick films, large pumping speed and a large oxygen flow rate condition result in comparatively better recoverability. The cyclic voltammograms of 500 nm films show small and balanced charge transfer, while those of 1000 nm films reveal large and unbalanced charge transfer. These indicate that more ions are intercalated into the 1000 nm samples but are not completely deintercalated. These findings contribute to the development of EC applications for light shielding.

Smart and Solar Greenhouse Covers: Recent Developments and Future Perspectives

The examination of recent developments and future perspectives on smart and solar greenhouse covers is significant for commercial agriculture given that traditional greenhouse relied on external energy sources and fossil fuels to facilitate lighting, heating and forced cooling. The aim of this review article was to examine smart and solar materials covering greenhouse. However, the scope was limited to intelligent PhotoVoltaic (PV) systems, optimization of some material properties including smart covers, heat loading and the use of Internet of Things (IoT) to reduce the cost of operating greenhouse. As such, the following thematic areas were expounded in the research; intelligent PV systems, optimization of the Power Conversion Efficiency (PCE), Panel Generator Factor (PGF) and other material properties, heat loading future outlook and perspectives. The intelligent PV section focused on next-generation IoT and Artificial Neural Networks (ANN) systems for greenhouse automation while the optimization of material parameters emphasized quantum dots, semi-transparent organic solar cells, Pb-based and Pb-based PVs and three dimensional (3D) printing. The evaluation translated to better understanding of the future outlook of the energy-independent greenhouse. Greenhouse fitted with transparent PV roofs are a sustainable alternative given that the energy generated was 100% renewable and economical. Conservative estimates further indicated that the replacement of conventional sources of energy with solar would translate to 40–60% energy cost savings. The economic savings were demonstrated by the Levelized cost of energy. A key constraint regarded the limited commercialization of emerging innovations, including transparent and semitransparent PV modules made of Pb-quantum dots, and amorphous tungsten oxide (WO3) films, with desirable electrochromic properties such as reversible color changes. In addition to intelligent energy harvesting, smart IoT-based materials embedded with thermal, humidity, and water sensors improved thermal regulation, frost mitigation and prevention, and the management of pests and disease. In turn, this translated to lower post-harvest losses and better yields and revenues.

Electric field-induced crystallization of ferroelectric hafnium zirconium oxide

Ferroelectricity in crystalline hafnium oxide thin films is strongly investigated for the application in non-volatile memories, sensors and other applications. Especially for back-end-of-line (BEoL) integration the decrease of crystallization temperature is of major importance. However, an alternative method for inducing ferroelectricity in amorphous or semi-crystalline hafnium zirconium oxide films is presented here, using the newly discovered effect of electric field-induced crystallization in hafnium oxide films. When applying this method, an outstanding remanent polarization value of 2P_{mathrm{R}} = 47 upmuC/cm^{2} is achieved for a 5 nm thin film. Besides the influence of Zr content on the film crystallinity, the reliability of films crystallized with this effect is explored, highlighting the controlled crystallization, excellent endurance and long-term retention.

Modifications of an electrolytic aluminum oxide film under the treatment with microdischarges during plasma electrolytic oxidation, a self-organized dielectric barrier discharge (DBD) and a DBD-like plasma jet

A key to the understanding of mechanisms during plasma electrolytic oxidation (PEO) is the interaction between microdischarges and an amorphous oxide film. The PEO microdischarges, which are randomly distributed on the surface of a treated lightweight metal substrate (Al, Ti, Mg), cause material extraction and support the formation of hard and dense crystalline oxide films. Characterization of these microdischarges is a complicated task under PEO conditions, because of the stochastically temporal and spatial behavior as well as the small dimension of the microdischarges. Microdischarges at atmospheric pressure conditions can leave similar erosion traces on metallic films (Al, Ti) as PEO microdischarges on oxide films, and possibly can support a better understanding of the plasma-solid-interactions as well as microdischarge characteristics during PEO. A porous aluminum oxide film is deposited on aluminum substrates by pre-anodizing at a voltage of 250 V and is treated afterwards with a relative short (duration of 1 min) PEO process at a voltage of about 500 V or filamentary dielectric barrier discharges, namely a self-organized Dielectric Barrier Discharge (DBD) and a DBD-like plasma jet operated both with a He/N2 (95%/5%) gas flow. The gas temperature at DBD plasma conditions, measured using the rotational distribution in the emission spectra of molecular nitrogen, is low and amounts to about 400 K. Erosion traces on the surface of the oxide film caused by PEO and plasma spots of both atmospheric pressure discharges are studied by scanning electron microscopy and energy dispersed x-ray spectroscopy. Form and dimensions of erosion traces and established modifications of the material composition generated by the treatment with these DBD microdischarges under atmospheric pressure conditions are similar to those ones generated by the PEO process. Hence, a similar mechanism of these processes is supposed. For stronger evidences of the assumed PEO mechanism additional experimental studies are needed.

Effect of O2 plasma exposure time during atomic layer deposition of amorphous gallium oxide

Amorphous gallium oxide thin films were grown by plasma-enhanced atomic layer deposition on (100) silicon substrates from trimethylgallium Ga(CH3)3 precursor and oxygen plasma. At 200 °C, the growth per cycle is in the range of 0.65–0.70 Å for O2 plasma exposure times ranging from 3 up to 30 s during each cycle. The effect of O2 plasma exposure times on the interfacial SiOx regrowth and the electrical properties was investigated. In situ spectroscopic ellipsometry shows that the SiOx regrowth occurs during the first three cycles and is limited to 0.27 nm for plasma times as long as 30 s. Increasing the O2 plasma exposure during each ALD cycle leads to a drastic decrease in the leakage current density (more than 5 orders of magnitude for 30 nm films), which is linked to the suppression of oxygen vacancy states as evidenced by spectroscopic ellipsometry. Interestingly, an increase in the dielectric constant with increasing O2 plasma exposure time is observed, reaching a value of εr∼14.2, larger than that of single crystalline β-Ga2O3. This study highlights the crucial role of oxygen plasma exposure time in the control and tuning of the electrical properties of amorphous gallium oxide films.

Increasing the oxygen dissociation degree in the plasma of a pulse-periodic Ar/O2 low-pressure arc

The results of a study on O2 dissociation conditions in the near-anode area of forcibly compressed low-pressure arc discharge are presented. A combined mode of discharge operation was applied to increase the O2 dissociation degree. In this mode, high-current pulses (up to 160 A) of short duration (100 μs) were imposed on a direct current discharge (up to 70 A). Probe measurements showed that a higher atomic oxygen concentration is caused by increasing not only the electron current, but also the voltage drop in the anode part of the discharge in the pulsed phase. A necessary condition for achieving high average values of O2 dissociation degree at high pulse ratio is the increased lifetime of oxygen atoms in the volume. This condition is fulfilled in a gas-discharge system with metal walls used for the deposition of oxide coatings through formation on the walls of amorphous oxide films, which have a low atomic oxygen recombination coefficient. An O2 dissociation degree of ∼0.4 in a low-pressure arc (less than 1 Pa) in Ar/O2 mixture was obtained by optimizing the parameters of the arc operation mode and the condition of the wall surface of the gas-discharge system.

Substrate-bias-aided preparation and properties of amorphous gallium oxide films and their deep-ultraviolet photodetectors

Amorphous gallium oxide (a-GaOx) thin films are fabricated via magnetron sputtering at room temperature by regulating the substrate bias voltage (Vs) in a wide range (0 ~ -184 V). The effect of Vs on the performance of a-GaOx films and their photodetector devices, such as the chemical composition, optical, morphological, and electrical properties, are systematically investigated. It's found that both the refractive index and the film relative mass density are highly dependent on the Ga/O ratio that can be effectively modified by the Vs. And the subband trap density or/and microvoid defects in a-GaOx films can be largely reduced under a well-selected Vs. The deep-ultraviolet photodetectors based on the optimized a-GaOx thin films show a responsivity of nearly 13 A/W with an ultrahigh UV/vis. rejection ratio. The research suggests that substrate bias voltage may be a feasibly subsidiary method for low-temperature magnetron sputtering technology with respect to the quality control of a-GaOx films.