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Among chromogenic materials, tungsten trioxide (WO3) is of great interest. It is a colourlesssemiconductor characterised by a lack of toxicity and high chemical stability. WO3 exhibits gasochromicproperties, meaning that the material undergoes reversible changes in optical properties when it isexposed to gas. These properties make tungsten oxide a suitable material for sensing applications. Thispaper presents the results of an analysis of the surface, structural and optical properties of tungstenoxide thin films fabricated by electron beam evaporation and annealed at 400C to 800C. Opticalproperties, including gasochromic properties, were determined from light transmission spectra inan atmosphere containing hydrogen at the concentrations ranging from 50 ppm to 500 ppm. Theoptical properties of WO3 films without and with a palladium catalyst layer are applied. Annealing thesamples at temperatures above 400C resulted in crystallisation of the layers, and further post-processmodification at 800C led to sublimation, the formation of islands of crystalline grains of large size anda significant deterioration in optical properties. A change in the light transmission coefficient occurredfor all samples with the catalyst layer applied after the introduction of a hydrogen-argon mixture.Based on the results, it can be concluded that the layers annealed at 400C had the best gasochromic properties due to the greatest changes in light transmission under hydrogen. The study confirmsthat it is possible to improve the gasochromic response of tungsten trioxide thin films produced byelectron beam evaporation using thermal modification, which, to the best of current knowledge, hasnot previously been achieved.Keywords: electronics, WO3, electron beam evaporation, gasochromic properties, optical properties,annealing, optical hydrogen gas sensor

Tungsten trioxide (WO3) is a wide-bandgap semiconductor. Its advantages include highchemical stability and low price. Furthermore, WO3 has chromogenic properties, that is, the abilityto switch between pale yellow and dark blue in response to various stimuli, including temperature,light irradiation, electric field, and exposure to hydrogen. Due to its high colouring efficiency andfast switching, it can be used in antidazzling mirrors and smart window applications, as well as in gassensing. In this paper, we present the influence of annealing on the properties of WO3 coatings that wereannealed at temperatures in the range from 200C to 400C. The sensing response was characterisedbased on the transmittance measurement during exposure to air and Ar/H2 mixture with hydrogenconcentrations from 25 ppm to 1000 ppm. Furthermore, the influence of annealing on the structureand morphology of the coatings was examined. Annealing at 400C led to a structure change fromamorphous to crystalline one. After the introduction of the Ar/H2 mixture, a decrease in transmittancewas observed for all of the analysed coatings. For films annealed at 200C and 300C, the transmittancevalue decreased during the entire colouring cycle, while for the coating annealed at 400C a plateau wasreached after 7 minutes of exposure. It was found that the best sensing characteristics were obtained forthe WO3 thin film annealed at 400C due to high sensor response to very low hydrogen concentrations(SR = 6.3 for 25 ppm H2) as well as short response and recovery times.Keywords: electronics, tungsten oxide, thin film, gas impulse magnetron sputtering, gas sensingproperties

The subject of the current studies were mixtures of copper and titanium oxide thin films,with various elemental compositions, deposited by magnetron sputtering and annealed in the postprocess.The effect of elemental composition and annealing temperature on the morphology of thinfilms was determined using scanning electron microscope images. The crystal structure and chemicalcomposition of copper‒titanium oxide (CuTi)Ox mixtures were investigated by X-ray diffraction.Hydrogen gas sensing experiments were performed for hydrogen with concentrations ranging from 100to 1,000 ppm. The resistance of the prepared (CuTi)Ox mixtures increased during hydrogen exposure,demonstrating the applicability of these oxides in hydrogen sensing. In addition, better sensor responseswere obtained for the mixtures in comparison to single copper oxides or titanium oxides. Mixturesof copper oxides and titanium oxides may be promising materials for hydrogen sensor applications.Keywords: mixtures of copper and titanium oxides, hydrogen gas sensors, mixed copper and titaniumoxides, thin films, magnetron sputtering

This work presents an investigation of the effects of post-process annealing on the morphologyof mixed copper and titanium oxides and on their electrical and hydrogen sensing properties. (CuTi)Oxthin films were deposited by magnetron sputtering on amorphous silica and ceramic substrates withinterdigitated electrodes. In addition, post-process thermal treatment was applied at the temperaturesof 200C and 250C.The transformation of the thin film structure during the thermal oxidation process was studied byX-ray diffraction, while the morphology of the thin films was determined using an optical profilometer.Current-voltage and thermoelectric characteristics were measured to determine electrical properties,from which the resistance and conduction type were determined. The post-treatment (CuTi)Ox thinfilms exhibited hole-type conduction and, additionally, strongly responded to hydrogen atmosphere.Keywords: electronics, hydrogen gas sensors, mixed copper and titanium oxides, thin films, magnetronsputtering

In this article, optical and electrical properties of tungsten oxide thin films, prepared by magnetron sputtering in the atmosphere of various oxygen content, were analysed. Tungsten oxide is a material, which is widely used in modern applications such as smart windows, anti-steam mirrors, and gas sensors. Five sets of tungsten oxide thin films were deposited by magnetron sputtering in the mixed argon-oxygen atmosphere composed of various content of reactive gas, i.e., from 5% to 15%. In each case, other deposition process parameters were the same. The thickness of the thin films was ca. 160 nm and it was measured with the optical profilometer. It was noticed that along with the increase in the proportion of reactive gas in the process, thin film samples changed their colour from metallic, through navy blue to blue and simultaneously they became increasingly transparent. Measurements of electrical properties, made using the four-point probe and optical properties, performed with the aid of a spectrophotometer showed that increasing the proportion of oxygen in the process increased the average transmission in the visible wavelength range and the resistivity of the prepared WOx thin films. In the article, the Figure of Merit (FoM) coefficients are also presented, which determine the quality of the thin film samples. It was shown that the highest value of the FoM was observed for WOx thin film characterised by a relatively high average transmission in the visible wavelength range and low value of resistivity. The performed measurements showed that the gas atmosphere during magnetron sputtering process leads to the tailoring of the optical and electrical properties of tungsten oxide thin films, which in turn makes it possible to design and apply such thin film coatings in transparent electronics. Keywords: magnetron sputtering, thin films, tungsten oxide, optical and electrical properties