Au Thin Films Research Articles

Stable, reproducible, and binder-free gold/copper core–shell nanostructures for high-sensitive non-enzymatic glucose detection

The core–shell non-enzymatic glucose sensors are generally fabricated by chemical synthesis approaches followed by a binder-based immobilization process. Here, we have introduced a new approach to directly synthesis the core–shell of Au@Cu and its Au@CuxO oxides on an FTO electrode for non-enzymatic glucose detection. Physical vapor deposition of Au thin film followed by thermal annealing has been used to fabricate Au nanocores on the electrode. The Cu shells have been deposited selectively on the Au cores using an electrodeposition method. Additionally, Au@Cu2O and Au@CuO have been synthesized via post thermal annealing of the Au@Cu electrode. This binder-free and selective-growing approach has the merit of high electrooxidation activity owing to improving electron transfer ability and providing more active sites on the surface. Electrochemical measurements indicate the superior activity of the Au@Cu2O electrode for glucose oxidation. The high sensitivity of 1601 μAcm−2 mM−1 and a low detection limit of 0.6 μM are achieved for the superior electrode. Additionally, the sensor indicates remarkable reproducibility and supplies accurate results for glucose detection in human serums. Moreover, this synthesis approach can be used for fast, highly controllable and precise fabrication of many core–shell structures by adjusting the electrochemical deposition and thermal treatment parameters.

Correlation between interface perpendicular magnetic anisotropy and interfacial Dzyaloshinskii–Moriya interactions in Pt/Pd(t Pd)/Co(t Co)/Au

The interfacial Dzyaloshinskii–Moriya interaction (iDMI) and perpendicular magnetic anisotropy (PMA) can be manipulated via interface engineering. Their strength determines the generation and the size of skyrmions, and the correlation between the iDMI and PMA allows them to be controlled simultaneously, thus choosing the material parameters for which skyrmions can be formed. This opens up the possibility of synthesizing suitable magnetic multilayers that are needed for low-power high-density memory and in logic applications. Vibrating sample magnetometry (VSM), Brillouin light scattering (BLS), and microstrip ferromagnetic resonance (MS-FMR) were used to investigate the correlation between the iDMI and the interface PMA. For this, Pt/Pd(t Pd)Co(t Co)/Au thin film structures with 0 ⩽ t Pd⩽1.2 nm and 1.2 nm ⩽ t Co⩽3 nm were grown by combined sputtering and e-beam evaporation on Si/SiO2 substrates. VSM measurements revealed a negligible magnetic dead layer and a Pd thickness-independent magnetization at saturation of around 1200 emu cm−3. MS-FMR and BLS allowed us to conclue that PMA results from weak volume and interfacial contributions induced by Pd/Co or Pt/Co and Co/Au interfaces. The interface anisotropy constants are found to be 0.65 mJ m−2 and 0.85 mJ m−2 for Pd/Co and for Pt/Co interfaces, respectively. The Pd thickness-dependence of surface iDMI (D s) and PMA (K s) constants follow an exponential decay with a characteristic thickness higher for PMA than the iDMI. The slower decrease of K s vs Pd thickness suggests a shorter range of the iDMI with respect to PMA and points out a strongly localized origin for the iDMI. This difference between the iDMI and PMA is most likely responsible for the nonlinear correlation between PMA and iDMI constants. The investigation of the Co thickness-dependence of the iDMI and PMA in Pd/Co/MgO/Ta systems allows us to conclude a zero iDMI constant of Co/Au and to determine the iDMI constants of Pd/Co and Co/MgO, estimated to be D s Pd/Co = −0.096 pJ m−1 and D s Co/MgO = −0.15 pJ m−1, respectively. The criterion of skyrmions stability, applied for our samples, revealed the possibility of the existence of stable skyrmions in some samples.

Reactive Spray Deposition Technology As an Alternative Method for Precious Metals Deposition on Sintered Titanium Porous Transport Layers for Application in Advanced Proton Exchange Membrane Water Electrolyzers

The metal layer deposition technologies have been revolutionized throughout the years. One of the most common forms of thin metal film deposition techniques is Physical Vapor Deposition (PVD). Within the category of PVD, there are many modifications based on the source of deposition. Among all PVD variations, the Electron Beam Physical Vapor Deposition (EB-PVD) has the advantages of higher deposition rates, the ability to deposit a wide range of high purity metals for high purity films, and the creation of continuous film layers. [1,3]. EB-PVD is better known as a thermal vaporization technique. Thermal Vaporization focuses on a source, in this case an Electron Beam (EB), which bombards the desired source material with electrons. The electron beam increases the temperature of the porous metal source until it reaches its vapor phase. The metal vapor is then condensed onto the surface of the substrate holder perpendicular to the source material. While EB-PVD is known for its advantages of higher material utilization efficiency, higher deposition rates, and better step coverage [1], it lacks in its ability to penetrate into the volume of Porous Transport Layer (PTL) or coat surfaces that are not perpendicular to the source. This is important as the PTL is in contact with a corrosive environment, which causes metal corrosion and degradation of the PTL at the surfaces that are not protected by the coating.A key aspect plaguing the thin film deposition techniques is the ability to penetrate deep into the volume of a PTL and provide full coating of the porous material, including surfaces not perpendicular to the source. In an attempt to find a solution to this challenging task, we explored the capability of the Reactive Spray Deposition Technology (RSDT) to deposit precious metal nanoclusters directly onto all surfaces in the volume of the sintered titanium material [2]. The studied metal coating of interest is Gold (Au). In this work, we have deposited Au coatings of various thicknesses onto the Ti-PTLs by using both EB-PVD and RSDT techniques. The Au thin film deposits are characterized by scanning electron microscopy (SEM), digital optical microscopy, inductively coupled plasma (ICP), and focused ion beam scanning electron microscopy (FIB-SEM) [2]. The optimal deposition parameters for thin and continuous Au films with precisely controlled thicknesses have been identified. In addition, the depth of penetration of the deposits in the volume of the PTL as a function of the deposition parameters have been studied in detail, and the results will be reported at the ECS 242 meeting.

Properties of SiC and Si3N4 Thin Films Containing Self-Assembled Gold Nanoparticles

The properties of semiconductor materials can be strongly affected by the addition of metallic nanoparticles. Here we investigate the properties of SiC + Au and Si3N4 + Au thin films prepared by magnetron sputtering deposition followed by thermal annealing. The influence of gold addition on the optical and electrical properties is explored. We show the formation of self-assembled Au nanoparticles in SiC and Si3N4, with the size and arrangement properties determined by the deposition and annealing conditions. Both SiC- and Si3N4-based films show an increase in the overall absorption with increasing Au content, and its decrease with increasing annealing temperature. All films show the presence of surface plasmon resonance, whose peaks shift toward larger wavelengths with increasing Au nanoparticle size. The resistivity significantly drops with the Au content increase for both types of matrices, although the resistivity of Si3N4-based films is much higher. The incorporated quantity of Au in the host matrix was chosen in such a way to demonstrate that a huge range of optical and electrical characteristics is achievable. The materials are very interesting for application in opto-electronic devices.

SPR Sensor Based on a Tapered Optical Fiber with a Low Refractive Index Liquid Crystal Cladding and Bimetallic Ag-Au Layers.

This paper presents a study of the influence of bimetallic layer covers of a tapered optical fiber surrounded by a low refractive index liquid crystal on the properties of light propagation in the taper structure. This research follows previous works on the effect of monometallic thin films (Au and Ag). In this case, the total thicknesses of the bimetallic layers were h = 10 nm, and the participation of gold and silver was equal. The films were deposited on one side of the tapered waist area. The liquid crystal cells were controlled with a voltage U from 0 to 200 V, with and without amplitude modulation at a frequency of fmod = 5 Hz. For the purposes of this research, spectral characteristics were obtained for a wavelength λ ranging from 550 to 1200 nm. Measurements were carried out at room temperature for three types of rubbed layers orientation—orthogonal, parallel, and twist in relation to the fiber axis. Obtained resonant peaks were compared with the previous results regarding the resonant wavelength, peak width, SNR, and maximum absorption. In the presented paper, the novelty is mainly focused on the materials used and their time stability, as well as corresponding changes in the technological parameters used.

Tunable fano resonance-enhanced surface plasmon biosensor based on MXene/MoS2 heterostructure

Two-dimensional materials have unique physical properties such as high electrical conductivity, excellent light absorption, and hydrophilicity, thus have been widely used as responsive materials for surface plasmon effect sensors in recent years. Here, we propose a Kretschmann configuration-based MXenes/MoS2 heterostructure film material as an improved sensing layer for surface plasmon resonance (SPR) sensors and introduce an optical waveguide layer into the nanostructure to achieve a remarkable Fano resonance (FR). By separately adjusting the thickness and refractive index of the coupling dielectric and optical waveguide layers, the effective coupling between the surface plasmon polarization and the planar optical waveguide mode is achieved, which significantly improves the sensor's response performance to biomolecules and achieves high sensitivity (S, 86.13°/RIU) and better figure of merit (FOM, 281.74 RIU−1) in the visible red range (around 632.8 nm). Benefiting from the light absorption gain of the heterostructure and the FR effect, the FOM of the MXene/MoS2 Fano resonance sensor (FRS) is improved by 7.1 times compared to the traditional SPR sensor based on noble metal Au (50 nm thickness) thin film.

Fabrication and Characterization of Plasmonic Au Nanoparticles on ITO-Coated Glass Sheets

We report here the fabrication of sputter-deposited Au nanoparticles on ITO (Sn-doped indium oxide)-coated glass substrate. The effect of varying annealing parameters, viz., time and temperature in conjunction with varying thickness parameters has been thoroughly investigated. Synthesized Au nanoparticles were characterized using a field emission scanning electron microscope (FE-SEM), Rutherford backscattering (RBS) measurement, X-ray diffraction (XRD), and optical absorbance spectroscopy. The role of annealing temperature and time duration on the evolution of Au nanoparticles has been discussed in detail based on optical absorbance spectroscopy. The present study shows that 5 nm thickness Au thin film which was annealed at 500 °C for 90 min exhibited the strongest surface plasmon resonance (SPR) effect.

Influence of grain boundary density on the surface energy of nanocrystalline metal thin films

Owing to the proliferation of nanomaterials, the precise measurement of surface energy (SE) has gained importance because of their large specific surface area. Grain boundary (GB) density is a critical factor determining surface characteristics of nanoscale metals. However, the relationship between GB and SE of nanocrystalline metals has not been revealed thus far due to the limited technology to measure surface energy at nanoscale. Herein, we report the role of GB density (DGB) in determining the SE of nanocrystalline Au thin films. The surface energies of nanocrystalline Au with different DGB values were characterized using atomic force microscopy (AFM) in the PeakForce quantitative nanomechanical (PF-QNM) imaging mode. The adhesion forces in the PF-QNM imaging mode, measured at the nanoscale, were converted to SE. The measured adhesion force decreased as the DGB of the nanocrystalline Au thin film increased. In addition, all-atom molecular dynamics simulations showed that the work required for separating the AFM tip from the sample surface decreased as the DGB of the Au film increased owing to the low load transfer capability at the GBs. Consequently, the SE of nanocrystalline Au (SEnc) was confirmed to be inversely proportional to the DGB, i.e., SEnc ∝ 1/ DG.B.

Stretchable and Directly Patternable Double-Layer Structure Electrodes with Complete Coverage

Stretchable electrodes are widely used in next-generation wearable electronics. Recent studies incorporated designs that help rigid electrodes attain stretchability. However, these structures exhibited unsatisfactory charge/signal extraction efficiency because of their low areal fill factor. Additionally, they cannot be photolithographically patterned on polymer substrates because of their low adhesion, requiring additional complicated fabrication steps. We developed photolithographically patternable stretchable electrodes with complete coverage and enhanced charge-extraction efficiency. The electrodes, comprising double layers, included a chemically treated Ag nanowire mesh and Au thin film. The interfacial linker role of polyvinylpyrrolidone chemically strengthened the interfacial bonds, and the reinforced concrete structure of nanowire-embedded metal thin films enhanced the mechanical properties. Therefore, the electrodes provided superior efficiency and stability in capturing physical, electromagnetic, and electrophysiological signals while exceeding the existing stretchable electrode limits. A broad range of applications are foreseen, such as electrocardiogram sensing electrodes, strain sensors, temperature sensors, and antennas.

Optical properties of Au-Hf thin films

The optical properties of thin films of intermetallic Au$_{3}$Hf were experimentally investigated for the first time, which display clear plasmonic properties in the optical and near infrared region with negative permittivity. In contrast to similar alloys, such as films of Au$_{3}$Zr, the films express more negative $\epsilon'$ values and lower $\epsilon''$ values across most of the wavelengths (370-1570 nm) investigated. The Au$_{3}$Hf films were fabricated by DC magnetron sputtering at a range of deposition temperatures, from room temperature to 415$^{o}$C, and annealed at different vacuum levels. The films mostly formed as a combination of Au$_{3}$Hf, Au$_{2}$Hf and Au$_{4}$Hf phases when deposited below 400$^{o}$C, and exclusively Au$_{3}$Hf phase at above 400$^{o}$C, indicating key conditions for isolating this phase. The films were stable when annealed at 10$^{-8}$ Torr, but when annealed again at 10$^{-6}$ Torr the films oxidised and changed into a mix of Au- Hf phases, suggesting resistance to oxidization may be an issue for un-encapsulated applications at elevated temperatures.

Thermal dewetting as a method of surface modification of the gold thin films for surface plasmon resonance based sensor applications

Here, we report a quick and simple approach with low, optimized production costs to obtain surface plasmon resonance (SPR) based sensors fabricated through a time- and resource-effective method based on thermal dewetting of thin Au films. From the applicative point of view, the method of detection presented here should be easier to implement, since light transmission measurements seems to be much less challenging than light refractive index changes measurements conducted by many authors. Metallic films with nanometric thickness were deposited by magnetron sputtering method on a Corning 1737 glass substrates. Plasmonic nanostructures were formatted as a result of thermal annealing of the films. The detection repeatability, selectivity, and sensibility of manufactured devices were investigated. For this purpose, many verification tests were performed. The quality of the plasmonic nanostructures used for the detection was examined by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and ultraviolet-visible spectroscopy (UV–VIS). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) spectra showed the absence of any signs of structure degradation after several cycles of detection in the liquid environment. The surface plasmon resonance position of the achieved sensors was linearly changeable in correlation with the ethanol concentration, which translates into their high robustness. Such a simply prepared sensing device showed key features desired in the detection in the liquids area, which opens up the possibility of large-scale commercial production.

Hetero-core structured fiber optic chemical sensor based on surface plasmon resonance using Au/lipid films

In this study, a novel chemical sensor is developed based on the surface plasmon resonance (SPR) on hetero-core structured optical fibers with double-layer films of gold and lipid. Two lipids, namely, oleic acid and phosphoric acid di(2-ethylhexyl) ester (PAEE), were applied to the fiber surface. We observed different shifts of the SPR resonant wavelength and changes in the spectral width for different chemical solutions (i.e., quinine, hydroquinidine, gramine, and caffeine) whose refractive indices are close to each other. The shifts in the SPR resonant wavelength of the Au-coated sensor with oleic acid and PAEE were 22.0 and 14.5 nm for quinine, 20.7 and 12.4 nm for hydroquinidine, -3.4 and 9.2 nm for gramine, and 0 and 0.1 nm for caffeine, respectively. The Au-coated SPR sensor without a lipid membrane did not show these differences, implying different chemical interactions between the lipid and chemicals would occur and change the dielectric functions of the coated lipid films. The oleic acid-coated sensor with thin Au films provided a rapid time response within 2 s. In summary, the proposed lipid-coated sensor with thin Au films facilitates chemical sensing in a limited area, such as the rhizosphere.

Launching Coherent Acoustic Phonon Wave Packets with Local Femtosecond Coulomb Forces.

Generation and manipulation of coherent acoustic phonons enables ultrafast control of solids and has been exploited for applications in various acoustic devices. We show that localized coherent acoustic phonon wave packets can be launched by ultrafast Coulomb forces in a scanning tunneling microscope (STM) using tip-enhanced terahertz electric fields. The wave packets propagate at the speed of the longitudinal acoustic phonon, creating standing waves up to 0.26THz for a 6.4nm thin Au film on mica. The ultrafast lattice displacement can be as large as 5pm and is precisely controlled by varying the tip-sample distance. This nonthermal femtosecond Coulomb-force-based excitation mechanism is applicable in nano-optomechanics for advanced terahertz engineering and opens new perspectives in exploiting coherent phonons at the atomic scale.

All angle polarization-independent photonic spin Hall effect

The photonic spin Hall effect (PSHE) is inherently a polarization-dependent phenomenon of incident light. In this work, the Spin-Orbit coupling of light-led PSHE has been manipulated to vanish its polarization dependency for all incident angles. This work demonstrates that the horizontal (H) and vertical (V) polarized PSHE will remain the same; (δ±H=δ±V) for any plane-polarized incident wave at any incident angle. Equal absolute Fresnel reflection coefficients (rs=rp) and their equal angular derivatives ∂rp/∂θi and ∂rs/∂θi are the underlying conditions for polarization-independent PSHE (PI-PSHE), which is achieved from the reflected light through a glass-metal (Ag, Au, or Al) thin film interface. Furthermore, the provided assembly of the planar metal-dielectric interface allows for controlling the device's characteristic size in an extensive range from 0.1λ to any bulk size, just by adjusting the thickness of the covered thin glass layer. We believe that our findings will pave the way for the development of new polarization-independent nano-photonic devices.

In Situ Stress Generation during Oxygen Evolution and Reduction Reactions on Au Positive Electrode in Li-O2 Batteries

Li-O2 batteries have received enormous interest from the scientific community due to its extremely high theoretical specific energy density, which is originated from the oxygen reduction reactions during discharge at the surface of the cathode electrode. Unfortunately, the commercial implementation of this technology is hindered by the poor cycling performance, mostly due to the sluggish oxygen evolution/reduction kinetics and the nature of the discharge reaction product. The lithium peroxide (Li2O2) is the discharge reaction product and its insulating nature limits to harvest the theoretical capacity of the Li-O2 batteries practically. The impact of the salt and solvent species on the formation mechanisms of the discharge product has been reported widely. However, underlying mechanisms dictating the reaction pathway is still under debate.In this study, we employed in situ stress measurement to investigate the impact of the electrolyte salt on nanoscale dynamic changes on the surface of the thin Au film cathode (1-D) during charge / discharge of Li-O2 batteries. Stress measurements have been applied to various electrochemical and electrocatalytic application areas in order to probe the dynamic changes on the surface of the materials. The electrolyte was prepared by mixing 1 M LiTFSI or LiNO3 salts in DMSO or Diglyme solvents. Electrolytes were saturated either with oxygen or argon prior to performing electrochemical measurements. In situ stress measurements were conducted using a multiple beam optical sensor (MOS). A custom cell was designed to monitor the physical response of the cathode during cycling while enabling optical access to the back of the substrate for stress measurements1. In situ curvature evolution on Au thin film cathode was monitored during discharge and charge via galvanostatic cycling and cycling voltammetry.In this talk, we will present the impact of the electrolyte salt on the potential-dependent surface stress generation during the formation and oxidation of electrochemical redox reaction products at nanoscale on the Au thin film cathode. Shortly, in situ stress measurements pointed out the contribution of charge-induced stress, electrostriction stress, and intrinsic stress associated with the formation of discharge reaction products. Revealing the mechanical response of the discharge products on cathode electrode will shed light into the formation mechanisms of these products, which is crucial to design new electrolyte and cathodes for Li-O2 batteries.Acknowledgement:This work was supported by the Binational Science Foundation (#2018327), and we are thankful to both Dr. Malachi Noked and Rosy for fruitful discussions.

Sample Preparation and Experimental Design for In Situ Multi-Beam Transmission Electron Microscopy Irradiation Experiments.

There is a need to understand materials exposed to overlapping extreme environments such as high temperature, radiation, or mechanical stress. When these stressors are combined there may be synergistic effects that enable unique microstructural evolution mechanisms to activate. Understanding of these mechanisms is necessary for the input and refinement of predictive models and critical for engineering of next generation materials. The basic physics and underlying mechanisms require advanced tools to be investigated. The in situ ion irradiation transmission electron microscope (I³TEM) is designed to explore these principles. To quantitatively probe the complex dynamic interactions in materials, careful preparation of samples and consideration of experimental design is required. Particular handling or preparation of samples can easily introduce damage or features that obfuscate the measurements. There is no one correct way to prepare a sample; however, many mistakes can be made. The most common errors and things to consider are highlighted within. The I³TEM has many adjustable variables and a large potential experimental space, therefore it is best to design experiments with a specific scientific question or questions in mind. Experiments have been performed on large number of sample geometries, material classes, and with many irradiation conditions. The following are a subset of examples that demonstrate unique in situ capabilities utilizing the I3TEM. Au nanoparticles prepared by drop casting have been used to investigate the effects of single ion strikes. Au thin films have been used in studies on the effects of multibeam irradiation on microstructure evolution. Zr films have been exposed to irradiation and mechanical tension to examine creep. Ag nanopillars were subjected to simultaneous high temperature, mechanical compression, and ion irradiation to study irradiation induced creep as well. These results impact fields including: structural materials, nuclear energy, energy storage, catalysis, and microelectronics in space environments.

Comparative analysis of the sensitivity of nanometallic thin film thermometers

Thin film platinum resistive thermometers are conventionally applied for resistance thermometry techniques due to their stability and proven measurement accuracy. Depending upon the required thermometer thickness and temperature measurement, however, performance benefits can be realized through the application of alternative nanometallic thin films. Herein, a comparative experimental analysis is provided on the performance of nanometallic thin film thermometers most relevant to microelectronics and thermal sensing applications: Al, Au, Cu, and Pt. Sensitivity is assessed through the temperature coefficient of resistance, measured over a range of 10–300 K for thicknesses nominally spanning 25–200 nm. The interplay of electron scattering sources, which give rise to the temperature-dependent TCR properties for each metal, are analyzed in the framework of a Mayadas–Shatzkes based model. Despite the prevalence of evaporated Pt thin film thermometers, Au and Cu films fabricated in a similar manner may provide enhanced sensitivity depending upon thickness. These results may serve as a guide as the movement toward smaller measurement platforms necessitates the use of smaller, thinner metallic resistance thermometers.

Mechanically hot-pressed flattened plastic optical fiber-based SPR sensor and its RI sensing

This paper presents a surface plasmon resonance (SPR) sensor based on a flattened plastic optical fiber (POF) for refractive index (RI) sensing. The flattened POF is fabricated by mechanical hot pressing. Afterwards, a thin film of Ag and Au is first deposited on one side of the flat surface to excite the SPR effect. The results show that the flattened POF-based SPR probe coated with the Au film has a sharper SPR peak and a narrower peak width than the probe coated with Ag film. To improve the SPR effect, two flat surfaces of the flattened POF are coated with metal film (Ag and Au). It was found that the sensor showed better RI sensing performance compared to the sensor with only one flat surface coated with metal film. For the flattened POF with two flat surfaces coated with Ag film, achieving the highest RI sensitivity of 2507 nm/RIU in the RI range of 1.33–1.39. The proposed sensor is a low-cost solution for RI measurement with potential applications in the medical and biochemical fields.

Controllable Si oxidation mediated by annealing temperature and atmosphere

The morphology evolution by thermal annealing induced dewetting of gold (Au) thin films on silicon (Si) substrates with a native oxide layer and its dependences on annealing temperature and atmosphere are investigated. Both dewetting degree of thin film and Au/Si interdiffusion extent are enhanced with the annealing temperature. Au/Si interdiffusion can be observed beyond 800 °C and Au–Si droplets form in both argon and oxygen (Ar + O2) and argon and hydrogen (Ar + H2) environments. In Ar + O2 case, the passive oxidation (Si + O2 → SiO2) of diffused Si happens and thick silicon oxide (SiOx) covering layers are formed. A high temperature of 1050 °C can even activate the outward growth of free-standing SiOx nanowires from droplets. Similarly, annealing at 800 °C under Ar + H2 situation also enables the slight Si passive oxidation, resulting in the formation of stripe-like SiOx areas. However, higher temperatures of 950–1050 °C in Ar + H2 environment initiate both the SiOx decomposition and the Si active oxidation (2Si + O2 → 2SiO(g)), and the formation of solid SiOx is absent, leading to the only formation of isolated Au–Si droplets at elevated temperatures and droplets evolve to particles presenting two contrasts due to the Au/Si phase separation upon cooling.

Thermal synthesis of Ga2O3/SnO2 core–shell nanowires and their structural characterization

Ga2O3 core–SnO2 shell nanowires were synthesized by thermal evaporation of the metallic sources (Ga, Sn) in a horizontal quartz tube furnace at atmospheric pressure and in an oxidizing atmosphere. Au thin layers and 200 ppm Au colloid were applied as growth catalyst of Ga2O3 nanowires in vapor–liquid–solid method. Then the SnO2 shells were grown on the Ga2O3 nanowires cores. The configuration with highly sensitive shell and a relatively low conductivity core should enhance the efficiency of sensors based on these materials. Such narrowing of conductive area where a depletion of the charge carriers may occur, should increase the sensitivity, response and recovery time. The structural and material composition characterization of nanowires was performed by X-ray diffraction, energy-dispersive X-ray and Raman spectroscopy. The lattice parameters and strain of SnO2 shell were calculated. Using the catalyst in the form of a 200 ppm Au colloid compared to Au thin film, Ga2O3/SnO2 nanowires more similar to the core–shell structures were obtained.