Search

This paper presents a detailed analysis of aluminium-doped zinc oxide (AZO) thin films and considers them a promising alternative to indium tin oxide in transparent electrodes. The study focusses on critical properties of AZO, including optical, electrical, and mechanical properties, with potential applications in displays, photovoltaic cells, and protective coatings. The deposited AZO thin films are characterised by excellent optical and electrical parameters, with transparency in the visible light range exceeding 80% and resistivity of 10−3 Ω·cm, which gives a high value of figure of merit of 63. Structural analysis confirms the nanocrystalline nature of as-deposited AZO thin films, featuring hexagonal ZnO, orthorhombic Al2O3, and cubic Al2ZnO4 phases. The study includes nanoindentation measurements, which reveal exceptional hardness (11.4 GPa) and reduced elastic modulus (98 GPa), exceeding typical values reported in the literature, highlighting their protective potential. Abrasion tests have shown extraordinary scratch resistance due to the lack of impact on topography and surface roughness up to 10,000 cycles. This comprehensive study demonstrated that as-deposited AZO thin films are multifunctional materials with exceptional optical, electrical, and mechanical properties. The findings open up possibilities for a variety of applications, especially in protective coatings, where the combination of hardness, scratch resistance, and transparency is both rare and valuable. [ABSTRACT FROM AUTHOR]

Hydrogen gas sensors have recently attracted increased interest due to the explosive nature of H2 and its strategic importance in the sustainable global energy system. In this paper, the tungsten oxide thin films deposited by innovative gas impulse magnetron sputtering have been investigated in terms of their response to H2. It was found that the most favourable annealing temperature in terms of sensor response value, as well as response and recovery times, was achieved at 673 K. This annealing process caused a change in the WO3 cross-section morphology from a featureless and homogenous form to a rather columnar one, but still maintaining the same surface homogeneity. In addition to that, the full-phase transition from an amorphous to nanocrystalline form occurred with a crystallite size of 23 nm. It was found that the sensor response to only 25 ppm of H2 was equal to 6.3, which is one of the best results presented in the literature so far of WO3 optical gas sensors based on a gasochromic effect. Moreover, the results of the gasochromic effect were correlated with the changes in the extinction coefficient and the concentration of the free charge carriers, which is also a novel approach to the understanding of the gasochromic phenomenon. [ABSTRACT FROM AUTHOR]

Hydrogen is an efficient source of clean and environmentally friendly energy. However, because it is explosive at concentrations higher than 4%, safety issues are a great concern. As its applications are extended, the need for the production of reliable monitoring systems is urgent. In this work, mixed copper–titanium oxide ((CuTi)Ox) thin films with various copper concentrations (0–100 at.%), deposited by magnetron sputtering and annealed at 473 K, were investigated as a prospective hydrogen gas sensing material. Scanning electron microscopy was applied to determine the morphology of the thin films. Their structure and chemical composition were investigated by X-ray diffraction and X-ray photoelectron spectroscopy, respectively. The prepared films were nanocrystalline mixtures of metallic copper, cuprous oxide, and titanium anatase in the bulk, whereas at the surface only cupric oxide was found. In comparison to the literature, the (CuTi)Ox thin films already showed a sensor response to hydrogen at a relatively low operating temperature of 473 K without using any extra catalyst. The best sensor response and sensitivity to hydrogen gas were found in the mixed copper–titanium oxides containing similar atomic concentrations of both metals, i.e., 41/59 and 56/44 of Cu/Ti. Most probably, this effect is related to their similar morphology and to the simultaneous presence of Cu and Cu2O crystals in these mixed oxide films. In particular, the studies of surface oxidation state revealed that it was the same for all annealed films and consisted only of CuO. However, in view of their crystalline structure, they consisted of Cu and Cu2O nanocrystals in the thin film volume. [ABSTRACT FROM AUTHOR]

This paper reports results of investigations on selected properties of vanadium oxide thin films deposited using gas impulse magnetron sputtering and annealed at temperatures in the range of 423 K to 673 K. Post-process annealing was shown to allow phase transition of as-deposited films from amorphous to nanocrystalline V2O5 with crystallite sizes in the range of 23 to 27 nm. Simultaneously, annealing resulted in an increase in surface roughness and grain size. Moreover, a decrease in transparency was observed in the visible wavelength range of approximately 50% to 30%, while the resistivity of formed vanadium pentoxide thin films was almost unchanged and was in the order of 102 Ω·cm. Simultaneously, the best optoelectronic performance, testified by evaluated figure of merit parameter, indicated the as-deposited amorphous films. Performed Seebeck coefficient measurements indicated the electron type of electrical conduction of each prepared thin film. Furthermore, gas sensing properties towards diluted hydrogen were investigated for annealed V2O5 thin films, and it was found that the highest senor response was obtained for a thin film annealed at 673 K and measured at operating temperature of 623 K. [ABSTRACT FROM AUTHOR]

The paper presents the results of an investigation of the influence of technological parameters on the microstructure, optical, electrical and nanomechanical properties of zinc oxide coatings prepared using the pulsed reactive magnetron sputtering method. Three sets of ZnOx thin films were deposited in metallic, shallow dielectric and deep dielectric sputtering modes. Structural investigations showed that thin films deposited in the metallic mode were nanocrystalline with mixed hexagonal phases of metallic zinc and zinc oxide with crystallite size of 9.1 and 6.0 nm, respectively. On the contrary, the coatings deposited in both dielectric modes had a nanocrystalline ZnO structure with an average crystallite size smaller than 10 nm. Moreover, coatings deposited in the dielectric modes had an average transmission of 84% in the visible wavelength range, while thin films deposited in the metallic mode were opaque. Measurements of electrical properties revealed that the resistivity of as-deposited thin films was in the range of 10−4 Ωcm to 108 Ωcm. Coatings deposited in the metallic mode had the lowest hardness of 2.2 GPa and the worst scratch resistance among all sputtered coatings, whereas the best mechanical properties were obtained for the film sputtered in the deep dielectric mode. The obtained hardness of 11.5 GPa is one of the highest reported to date in the literature for undoped ZnO. [ABSTRACT FROM AUTHOR]

In this work, a complex examination of vanadium oxide thin films prepared by gas impulse magnetron sputtering with various Ar:O2 gas ratios of 2:1 ÷ 8:1 was conducted. X-ray diffraction revealed the amorphous nature of the prepared thin films, and scanning electron microscopy images showed that the thin films were crack-free and homogenous. Optical properties investigations revealed that a higher oxygen content in the Ar:O2 atmosphere during sputtering caused an increase in transparency. The sample prepared with the highest amount of oxygen in the gas mixture during deposition had 51.1% of the average transmission in the visible wavelength range. A decrease in oxygen caused deterioration in the thin film transparency with the lowest value equal to 21.8%. Electrical measurements showed that the prepared thin films had a semiconducting character with either electron or hole conduction type, depending on the sputtering gas composition. A small amount of oxygen in the gas mixture resulted in the deposition of p-type thin films, whereas an increase in the amount of oxygen caused a change to n-type electrical conduction. Resistivity decreased with increasing Ar:O2 ratio. The gas sensing response toward diluted hydrogen was investigated for all the VxOy thin films, but at low operating temperatures, only the p-type thin films exhibited a visible response. [ABSTRACT FROM AUTHOR]

[Display omitted] • XRD analysis results revealed that all deposited WO x thin films were amorphous. • Change of Ar:O 2 ratio in the sputtering atmosphere influenced WO x properties. • XPS results showed a decrease of O/W ratio from 3.01 to 2.55 for WO x thin films. • Increase of Ar:O 2 ratio caused the decrease of transmittance and band gap energy. • Electron and oxygen vacancy concentration increased with increase of Ar:O 2 ratio. • Ar:O 2 ratio of 7:1 was the best for use of WO x films in transparent electronics. In this paper, the structural, surface, optical, and electrical properties of tungsten oxide thin films were analyzed. Eight sets of WO x thin films were prepared using the magnetron sputtering method. In each case, the sputtering process parameters were the same, except the Ar:O 2 gas mixture ratios, which were intentionally changed from 1:1 to 10:1 to obtain various properties of the deposited thin film coatings. Structural properties analyzed with the aid of X-ray diffraction measurements results showed that all thin films were amorphous. X-ray photoelectron spectroscopy measurements revealed a shift of the binding energy for the W4f 7/2 peak towards lower energies for increasing Ar:O 2 ratio, indicating a possible change of stoichiometry and change of the oxygen vacancy concentration. It was also determined that the O/W atomic ratio at the surface of the thin films decreased from 3.01 to 2.55 with an increase of argon content in the magnetron sputtering atmosphere. Scanning electron microscope images revealed that all thin films had a smooth, homogenous, crack-free, and featureless, confirming the structural analysis. It was shown that the sputtering process atmosphere had a significant influence on the optical and electrical properties. Analysis of the transmittance spectra revealed that an increase of Ar:O 2 ratio caused a gradual decrease of the average transparency in the visible wavelength range, an increase of the fundamental absorption edge, and decrease of the optical band gap energy. Moreover, the refractive index and extinction coefficient were analyzed, showing that the change of the argon content in the sputtering atmosphere significantly influenced on those parameters. The sheet resistance and resistivity of the prepared WO x thin films decreased with the increase of Ar:O 2 ratio. The electrostatic charge dissipation times were measured for each coating to assess their antistatic properties. In turn, the hardness of tungsten oxide thin films increased with the increase of Ar:O 2 ratio. It was found that thin films deposited with Ar:O 2 ratio above 6:1 had good ability to dissipate static charge. Performed studies showed that a proper control of the gas atmosphere during magnetron sputtering of tungsten oxide thin films leads to tailoring their optoelectronic properties and creates an opportunity to design coatings destined for application in transparent electronics. [ABSTRACT FROM AUTHOR]

In this work, selected properties of metallic and oxide thin films based on titanium and cobalt were described. Thin-film coatings were prepared using the magnetron sputtering method. The deposition was carried out from sintered targets with different Co-content (2 at.%, 12 at.% and 50 at.%). The relation between the Ti–Co target composition and the Co-content in the metallic and oxide films was examined. There was 15–20% more cobalt in the films than in the target. Moreover, the deposition rate under neutral conditions (in Ar plasma) was even 10-times higher compared to oxidizing Ar:O2 (70:30) plasma. A comprehensive analysis of the structural properties (performed with GIXRD and SEM) revealed the amorphous nature of (Ti,Co)Ox coatings, regardless of the cobalt content in the coating. The fine-grained, homogenous microstructure was observed, where cracks and voids were identified only for films with high Co-content. Optical studies have shown that these films were well transparent (60% ÷ 80%), and the amount of cobalt in the target from which they were sputtered had a significant impact on the decrease in the transparency level, the slight shift of the absorption edge position (from 279 nm to 289 nm) as well as the decrease in their optical band gap energy (from 3.13 eV to 1.71 eV). Electrical studies have shown that in (Ti,Co)Ox thin films, a unipolar memristive-like effect can be observed. The occurrence of such effects has not been reported so far in the case of TiO2 coatings with the addition of Co. [ABSTRACT FROM AUTHOR]

• TiO 2 , WO 3 and mixed TiO 2 WO 3 thin films were deposited by electron beam evaporation. • For all prepared films reduction in the corrosion current density was observed. • Post-process annealing of the films affected the corrosion and mechanical properties. • The best corrosion resistance was obtained for (Ti 0.41 W 0.59)Ox film annealed at 800 °C. The paper focuses on the comparative studies on the structural, optical, corrosion and mechanical properties of TiO 2 , WO 3 and mixed TiO 2 WO 3 , i.e. (Ti 0.68 W 0.32)Ox and (Ti 0.41 W 0.59)Ox thin film coatings. Oxide thin films were prepared from WO 3 and Ti 3 O 5 pellets by electron beam evaporation method and were additionally annealed at 600 °C and 800 °C using tubular furnace. The microstructure of prepared coatings was analysed using scanning electron microscopy and X-ray diffraction. The transparency of as-deposited thin films was high, while annealing caused significant decrease of the transmission of TiO 2 and WO 3 coatings. In the case of mixed oxides such post-process treatment did not cause severe change of the optical properties. The corrosion properties of the thin films were examined by an analysis of the voltammetric curves, while mechanical properties were determined by nanoidentation measurements. The hardness of the (Ti 0.41 W 0.59)Ox film was approx. 3.42 GPa, but after annealing at 800 °C it increased to H it = 14.6 GPa. Preparation of the mixed titanium-tungsten oxidethin films caused a decrease of the electrochemical activity. The Ti6Al4V substrate coated with (Ti 0.41 W 0.59) Oxthin filmannealed at 800 °C exhibited the best corrosion properties among stprepared thin-film coatings. [ABSTRACT FROM AUTHOR]

In this work, a 500 nm-thick cerium oxide thin film was prepared by electron beam evaporation. It was found that the deposition of 7 nm thick Pd catalyst was required for obtaining a sensor response to hydrogen. The Pd/CeOx sensing structure has a high response of 5000 towards 25 ppm H 2 at a working temperature of 200 °C and exhibits a sensor response of 1.3 at temperatures near ambient. Furthermore, the sensing structure exhibited excellent response/recovery kinetics. The results confirm that the CeOx-based materials are a promising material for the fabrication of room-temperature hydrogen sensors. • Pd/CeOx thin film structures were prepared by e-beam deposition. • The Pd/CeOx structures demonstrate excellent sensitivity to low H 2 concentration. • Sensing response of 1.3 towards 25 ppm H 2 was achieved at 35 °C. • Sensor response was correlated with XPS results. [ABSTRACT FROM AUTHOR]

• Annealing caused an oxidation route from mixed Cu-Cu 2 O phase to pure CuO. • Thermal oxidation at 350 °C resulted in the development of CuO nanowire structure. • Thermal oxidation caused an increase in coating transparency in the Vis-NIR range. • All deposited and annealed Cu x O thin oxide films had p-type conductivity. • The best sensor response exceeding 13 was observed for film annealed at 200 °C. The paper presents the results of the investigation of the post-process annealing effect on selected properties of copper oxide thin films deposited by magnetron sputtering. It was found that the prepared thin films were nanocrystalline with the crystallite size smaller than 20 nm. Annealing at temperatures of 200 °C, 300 °C and 350 °C caused metallic copper oxidation to copper(I) oxide and then to copper(II) oxide. As-deposited and annealed at 200 °C thin films were composed of Cu and Cu 2 O. Copper(I) oxide transformation into CuO started at 300 °C, while the thin film annealed at 350 °C consisted of a single CuO phase. Scanning electron microscopy imaging revealed that annealing of the as-deposited thin films caused gradual formation of cupric oxide nanowires. Optimum annealing temperature for nanowires growth was 350 °C. X-ray photoelectron spectroscopy showed that the surface of the as-deposited thin films was oxidized to Cu 2 O and CuO, while in the case of annealed films it was completely oxidized to CuO. Thermal treatment also contributed to the increase in coating transparency in the infrared range. The transmission coefficient at 1500 nm of the thin film annealed at 350 °C was equal to 68. The resistivity of the as-deposited copper oxide thin film was equal to 1.9•10−3 Ωcm, while the highest resistivity of the annealed thin films was equal to 32 Ωcm for the coating annealed at 200 °C. A further increase in the annealing temperature resulted in a slight decrease in the resistivity value. Based on Seebeck coefficient measurements, it was found that all coatings were characterized by p-type conductivity. Additionally, sensing properties toward hydrogen were examined. The best sensor response exceeding 13 was observed for the thin film annealed at 200 °C. [Display omitted] [ABSTRACT FROM AUTHOR]