As-deposited Thin Films Research Articles

Enhancement of carrier concentration in chemical bath deposited copper sulfide (CuxS) thin film by post-growth annealing treatment

Copper sulfide thin films (CuxS, 1 ≤ x ≤ 2), owing to their unique optical and electrical properties, have attracted enormous attention in recent research. As one of the chalcogenide semiconductors, CuxS is used in several applications such as chemical sensors, photo-absorbing layers, photovoltaics, and lithium-ion batteries. In this study, copper sulfide thin film (CuxS; where 1 ≤ x ≤ 2) has been deposited by the chemical bath deposition method (CBD) at 27 °C with the molar ratio for copper and sulfur as 1:5, respectively. The structural, compositional, morphological, optical, and electrical properties of as-deposited and annealed CuxS thin films are investigated. From XRD plots, the presence of a mixture of two co-existing polycrystalline phases is observed, i. e. covellite phase with CuS stoichiometry and digenite phase with Cu1.8S stoichiometry up to an annealing temperature of 200 °C. At higher annealing temperatures, i.e. at 300 °C and 400 °C, the phase of CuxS thin film gets completely converted to digenite phase with Cu1.8S stoichiometry and chalcocite phase with Cu2S stoichiometry respectively. There is an enhancement in the crystallinity of CuxS thin film with an increase in annealing temperature as confirmed by XRD and Raman results. The optical bandgap of CuxS thin film is found to be decreased from 2.81 eV to 1.66 eV with an increase in the annealing temperature. The CuxS thin films are found to be p-type in nature, and the film annealed at 400 °C possesses the highest carrier concentration as revealed from the Hall effect measurement. This study aims to investigate the improvement of electrical properties of CuxS thin film with the variation in annealing temperature for optoelectronic applications such as photodetector.

Physical Properties of Nanostructured Zinc Sulfide Thin Films Deposited by the PLD Method for Gas Sensing

The pulsed laser deposition (PLD) technique created nanostructured semiconducting zinc sulfide (ZnS) thin films onto a quartz substrate. A gas sensing static unit, field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD) were used to analyze the structural, surface morphology, and gas sensing properties of the as-deposited thin films. After the ZnS thin films were formed, they were heated to evaluate the effects of annealing on the characteristics of the ZnS film. XRD analysis reveals that the ZnS thin films exhibit a structure similar to zinc blend cubes, with a preference for the (111) orientation. The X-ray diffraction (XRD) patterns that emerge during annealing show that ZnS thin films become more crystalline. Grain size increases as the annealing temperature rises. Images captured by field emission scanning electron microscopy (FESEM) revealed a grain-like sphere for each of the annealed thin films, confirming the growth of grains. The UV-Vis spectra showed that the ZnS samples' transmittance boosts after annealing because their crystalline quality is improved. The transmittance is measured within the 400 ̶ 900 nm band, and the optical band gap is direct at 3.72 eV, decreasing to 3.51 eV at 350 °C during annealing. Annealing significantly improves the physical properties of ZnS thin films, according to all presented data. NO2 and CO2 gas were used to obtain the I-V values ​​of the samples. The ability of ZnS thin films formed at different annealing temperatures was tested using NO2 gas. The sensors were fabricated and tested at different operating temperatures and NO2 gas concentrations of 100, 300, 400, 500, and 700 ppm.

Cobalt-doped ZnO nanoparticles and PLD-deposited thin film forms: structure, optical properties and nature of magnetic anisotropy.

Cobalt-doped zinc oxide nanoparticles (NPs) were synthesized using a modified sol-gel method. Thereafter, the obtained powder was deposited on a Suprasil glass substrate by employing a pulsed laser deposition (PLD) technique. X-ray diffraction analysis with Rietveld refinement confirmed a hexagonal wurtzite ZnO phase belonging to the P63 mc space group for both samples in the NP and thin film forms. In particular, the thin film exhibited an intensive (002) XRD peak, indicating that it had a preferred c-axis orientation owing to the self-texturing mechanism. No segregated secondary phases were detected. The crystallite structure, morphology, and size were investigated using high-resolution transmission electron microscopy (HRTEM). To study the crystalline quality, structural disorder, and defects in the host lattice, we employed Raman spectroscopy. UV-vis-NIR spectroscopy was performed to confirm the nature of the Co-doped ZnO NP powder and the film. The chemical states of oxygen and zinc in the thin film sample were also investigated via X-ray photoelectron spectroscopy (XPS). The M-T curve could be successfully fitted using both the three-dimensional (3D) spin-wave model and Curie-Weiss law, confirming the mixed state existence of weak ferromagnetic (FM) and paramagnetic (PM) phases. Magnetic interaction was quantitatively studied and explained by polaronic percolation of bound magnetic polarons (BMPs). Analysis of magnetic symmetry of the topological antiferromagnetic as-deposited thin film using torque measurements was performed. Based on a phenomenological model, it was revealed that the structure gives rise to uniaxial magneto-crystalline anisotropy (UMA) with the magnetic easy axis parallel to the c-axis.

In Situ Transmission Electron Microscope Observation of Ruthenium Silicadation and Diffusion Behavior at Atomic Scale

Ruthenium (Ru) has the excellent characteristics of oxidation resistance and good chemical stability; therefore, it has been widely used in semiconductor manufacturing, specifically in application as capping layers of extreme ultraviolet lithography (EUV) masks. The main purpose of capping layers is to protect Mo/Si multilayers from EUV radiation, preventing oxidation, damages, and contamination of the multilayers. However, with prolonged use, the EUV mask accumulates heat, resulting in diffusion between Ru and Si. When diffusion reactions occurred, leading to a reduction in the EUV mask's lifetime. In order to study the reaction mechanism, we use in-situ transmission electron microscopy (TEM) to observe the reactions between Ru and Si. In this study, Ru thin film was deposited on silicon substrate by electron gun (E-gun) evaporation. The dynamic formation process of ruthenium silicide has been observed via in-situ TEM. During the heating process, Si atoms diffused into ruthenium thin film at 300 °C, at the same time, Ru atoms will also diffuse into silicon substrate. At 350 °C, due to the interdiffusion effect, Ru2Si is formed in the Ru thin film, and it is observed that Ru2Si3 is embedded in the Si substrate. As the temperature rises to 450 °C, Ru2Si was transformed into RuSi. Finally, at 600 °C, the Ru thin film completely transformed into Ru2Si3. We provide direct evidence of diffusion behaviors and formation mechanism of Ru-Si system for better investigation of EUV masks degradation processes in semiconductor manufacturing and design. Keywords: Ruthenium silicide, in situ TEM, diffusion mechanism, atomic-scale, EUV mask Figure 1. Structural identification of Ru thin film and in-situ heating process of ruthenium silicide formation. (a) Initial EDS mapping of as-deposited Ru thin film on silicon substrate, showing homogenous distribution of each elements. (b) HRTEM image of in-situ heating process during 350oC. (c) Magnified HRTEM image of Ru2Si indicated in blue frame in (b). (d) Corresponding fast Fourier transform (FFT) along [110] zone axis. (e) HRTEM image of in-situ heating process during 600oC. (f) Magnified HRTEM image of Ru2Si3 indicated in yellow frame in (e). (g) Corresponding FFT along [010] zone axis. Figure 1

Effect of deposition regime transition on the properties of Al:ZnO transparent conducting oxide layer by radio frequency magnetron sputtering system

High-quality zinc oxide thin films doped with aluminium adatoms have effectively been fabricated on pristine soda-lime silica glass substrates via radio frequency magnetron sputtering system. The deposition temperature was varied to explore the impact of deposition regime transition of as-deposited Al:ZnO thin films on their performance as transparent conducting oxide layers. In particular, the depositions were conducted at room temperature, 100 °C, 200 °C, and 300 °C, allowing for a comprehensive assessment of the resulting films. The Raman spectra depicted the modulation of Raman bands in correlation with the deposition regime transition, illustrating the impact of thermal induction on various properties of the as-deposited aluminium-doped zinc oxide thin films. Atomic force microscopy reveals the transformation from nearly spherical to elongated shape structure was obtained as the deposition process shifted from kinetic limited to thermodynamic limited regimes. The phase analysis and grazing incident of x-ray diffractometer disclose a single crystal orientation has been achieved at thermodynamic limited regime. However, two different crystal planes were predominant comparing between the surface and structural of as-deposited aluminium-doped zinc oxide thin films. It is also evident that a highly transparent with low lattice strain and better carrier concentrations of as-deposited aluminium-doped zinc oxide thin films were realized at thermodynamic limited regimes.

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

Doped SnO2 thin films fabricated at low temperature by atomic layer deposition with a precise incorporation of niobium atoms

Nb-doped SnO2 (NTO) thin films were synthesized by atomic layer deposition technique at low temperature (100 °C). For an efficient incorporation of the Nb atoms, i.e. fine control of their amount and distribution, various supercycle ratios and precursor pulse sequences were explored. The thin film growth process studied by in-situ QCM revealed that the Nb incorporation is highly impacted by the surface nature as well as the amount of species available at the surface. This was confirmed by the actual concentration of the Nb atom incorporated inside the thin film as determined by XPS. Highly transparent thin films which transmit more than 95% of the AM1.5 global solar irradiance over a wide spectral range (300–1000 nm) were obtained. In addition, the Nb atoms influenced the optical band gap, conduction band, and valence band levels. While SnO2 thin film were too resistive, films tuned to conductive nature upon Nb incorporation with controlled concentration. Optimal incorporation level was found to be ⩽1 at.% of Nb, and carrier concentration reached up 2.5 × 1018 cm−3 for the as-deposited thin films. As a result, the high optical transparency accompanied with tuned electrical property of NTO thin films fabricated by ALD at low temperature paves the way for their integration into temperature-sensitive, nanostructured optoelectrical devices.

Ti3C2 MXene interfaced ZnO/CuO heterojunction for superior visible light PEC water splitting

A dual heterostructure was developed to explore the visible-light-driven photoelectrochemical (PEC) water splitting activity. Specifically, the growth of as-deposited ZnO and CuO thin film nanostructures on two-dimensional (2D) Ti3C2 MXene (Ti3C2/ZnO/CuO) demonstrated the potential visible light response. X-ray diffraction studies revealed predominant reflections of ZnO (002), CuO (002), and Ti3C2 (002), indicating successful structural integration within the Ti3C2/ZnO/CuO heterostructure. Surface morphology analysis showed vertical growth of CuO nanocrystals on flake-like ZnO (ZnO/CuO), resulting in the controlled growth of the ZnO/CuO heterostructure on layer-structured 2D Ti3C2 MXene. This progressive growth of ZnO/CuO and Ti3C2/ZnO/CuO modulated the optical absorption edge towards higher wavelengths than UV-active ZnO. Consequently, Ti3C2/ZnO/CuO showed an improved visible light response compared to ZnO/CuO and pure ZnO. The structural integration and band alignment in ZnO/CuO facilitated the rapid charge carrier separation from CuO to ZnO. Furthermore, forming a Schottky junction between Ti3C2 and ZnO resulted in enhanced charge carrier separation from ZnO to Ti3C2. The Ti3C2/ZnO/CuO heterostructure showed significant improvement in photocurrent generation (6.4 × 10−5 A/cm2) compared to ZnO/CuO (2.2 × 10−5 A/cm2) and ZnO (2.5 × 10−6 A/cm2) at +0.4 V. Overall, these results reveal the great potential of CuO and ZnO nanostructures growth on 2D Ti3C2 MXene for promising visible-light-driven PEC activity.

Facile synthesis and characterization of PbS thin films doped with various aluminum concentrations for photovoltaic applications

In this study, aluminum doped lead sulfide (PbS:Al) thin films were deposited on soda lime glass substrates using chemical bath deposition (CBD) technique. The structural, morphological, optical and electrical properties of as-deposited PbS thin films were studied as a function of Al concentration (0, 2, 4, 6, 8 at. %). The deposited films can be analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), UV-Vis-NIR spectroscopy and Hall measurement. From SEM, it was evident that the thickness of the films decreased from 750 nm (0 at. %) to 280 nm (8 at. %) with increased Al concentration. XRD analysis revealed that the prepared films exhibited face centered cubic structure without any other binary phases. The average crystallite size of the films decreased from 33.71 to 20.45 nm. The direct optical band gap values were increased from 0.90 to 1.29 eV. The optical parameters such as refractive index (n), extinction coefficient (k), real (ɛ 1) and imaginary (ɛ 2) parts of the dielectric constant were 1.51–2.04, 0.0035–0.0075, 2.50–6.20 and 0.005–0.16 respectively. The absorption coefficient (α) of all the deposited films was in the range of ≈105 cm−1. The electrical resistivity of the deposited films was found in the range of 102–103 Ω·cm. The overall analysis indicate that the deposited PbS:Al thin film shows promise as an absorbing layer for heterojunction solar cell devices.

Narrow-band n-GaN/n-Si isotype heterojunction photodiode: A simplified approach for photodiode development

An innovative approach has been explored to fabricate a high-performance photodiode in semiconductor device production, utilizing the thermal evaporation technique to grow GaN thin films. Structural analyzes were conducted on both as-deposited and annealed samples, and their properties were determined using various characterization techniques, including FESEM, XRD, XPS, Hall effect, photoluminescence, and UV-Vis spectrophotometer measurements. Valuable information has been gained about the potential of this alternative approach for fabricating GaN-based electronic devices. In this study, Al/n+-GaN/n-Si/Ag (as-deposited GaN) and Al/n-GaN/n-Si/Ag (annealed GaN) structures have been fabricated. It was found that the device produced from the as-deposited GaN thin film exhibited better performance than the annealed one. The isotype heterojunction n+-GaN/n-Si photodiode exhibited exceptional performance in detecting NIR light at a wavelength of 1050 nm under a 0 V bias. It has a full-width at half-maximum (FWHM) value of 120 nm and achieved a photoresponsivity value of 355 mA/W at a light output of 10 mW/cm². It is further supported by its external quantum efficiency of 42% and detectivity value of 6.93×1011 Jones at the peak wavelength and very fast response speed with ∼33 µs rise/fall times. These findings highlight the potential of photodiode as an efficient narrow-band in the NIR region.

Investigation on thermoelectric properties of SnSe thin films as prepared by RF magnetron sputtering

In this work, we investigated the thermoelectric properties of SnSe (Tin Selenide) thin films onto SiO2/Si-wafer substrates as prepared by RF (radio frequency) magnetron sputtering technique. The sputtering conditions used base pressure below 5.5 10−4 Pa and working pressure at 0.93 Pa within the Ar atmosphere as a flow rate fixed 40 sccm. The RF sputtering power was applied at 80 W and sputtering time for 30 min. After thin film deposition, as-deposited thin films were annealed by the vacuum annealing method at 300–450 °C. The crystal structure, morphology and film thickness, and atomic composition of SnSe thin film were carried out by X-ray diffraction (XRD), the field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques, respectively. The thermoelectric properties (electrical resistivity; ρ) and Seebeck coefficient; S) were measured by the ZEM-3 method to calculate the power factor (PF) value. The results showed that the as-deposited thin films had improved the crystallography of SnSe from amorphous to crystalline phases after thin films were annealed at a temperature range of 300–400 °C. At room temperature, the maximum power factor of 0.35 mW m˗1 K˗2 (ρ = 202 mΩ m and S = 165 μV K˗1) could be found to estimate the dimensionless Figure of Merit (ZT) values around 0.44 for annealing thin film sample at 400 °C.

Synthesis and characterization of Co3O4 spinel nanowall: understanding the growth mechanism and properties

Formation of spinel tricobalt tetraoxide (Co3O4) nanostructures through a controlled thermal oxidation process is discussed here. Thin films of high purity cobalt (Co) were deposited on glass/quartz substrates using an electron beam (E-beam) evaporation technique. Thermal oxidation of the as-deposited Co thin films was carried out at various oxidation temperatures (400 °C to 600 °C) for different durations (5 h to 15 h) to grow various oxide nanostructures. Different surface characterizations techniques were used to investigate the structure, chemistry and electronic properties of the as-grown cobalt oxide nanostructures. x-ray diffraction analysis revealed the presence of the CoO phase along with the Co3O4 phases at relatively lower oxidation temperature. However, the Co3O4 phase becomes more predominant for longer oxidation durations at higher oxidation temperatures. Field emission scanning electron microscopy analysis showed a surface morphological transition from nanowalls to nanograins with an increase in the oxidation temperature. The surface electrical conductivity of the oxidized Co films is also increased for higher oxidation temperature and/or duration mainly due to the oxide phase purity and larger particle sizes. Ultraviolet–visible spectroscopy indicated two distinct optical energy bandgaps, which effectively decreased with an increase in the oxidation temperature and duration. Raman spectroscopy identified five different Raman-active modes corresponding to the Co3O4 phase, with the F2g mode dominating at higher temperatures. All these findings provide clear insights into the structural, electrical, chemical and optical properties of cobalt oxide thin films. Moreover, it provides a mechanism on how to grow 2D nanowalls morphology of Co3O4 films which can further be used in energy, sensor or catalytic applications.

Secondary Phases, Morphology and Band Tails of Third Generation Photovoltaic Absorber Layer CZTS Annealed at Different Temperatures

Abstract: In this work, we have successfully fabricated Cu2ZnSnS4 (CZTS) thin films using the sol-gel spin-coating technique. Thin films were annealed in an argon atmosphere at different temperatures of 350, 375, 400, 425, and 450 ℃ for an hour. The influence of annealing temperature on structural, morphological, and optical properties was investigated. x-ray diffraction measurement confirmed the formation of secondary phases in as-deposited and annealed thin films at 350 and 375 ℃. A pure kesterite phase was obtained at an annealing temperature of 400 ℃, but degradation occurred at higher temperatures. The morphology study of the surface structure showed that thin films have homogeneous surfaces. The Volmer-Weber mode was the dominating growth mode. The as-deposited and annealed CZTS thin films exhibited a high absorption coefficient of the order of 104 cm-1, and the optical energy band gap Eg was red-shifted with increasing annealing temperature. The optical study showed a decrease in Urbach tail energy with an increase in annealing temperature and reached 0.39 eV at 400 ℃. The refractive index and dielectric constants of CZTS thin films were calculated. Keywords: Cu2ZnSnS4 thin films, Sol-Gel technique, Secondary phases, Roughness parameters, Band gap, Urbach tails.

Chemical bath deposited CdTe thin film: Optical, electrical, and photoresponse aspects

Owning a narrow bandgap, remarkable optical and electrical properties with notable stability has made cadmium telluride (CdTe) an immensely vital semiconductor to develop cutting-edge optoelectronics. Taking these properties in to account, CdTe thin film is deposited employing the chemical bath deposition (CBD) technique. The X-ray diffraction analysis of the as-deposited thin film unveiled the composite crystalline structure, incorporating cubic, hexagonal, and tetragonal phases. The energy dispersive X-ray analysis and X-ray photoelectron spectroscopy ascertained the chemical composition of CdTe thin film. Distinctive Raman peaks are detected at 141 and 167 cm−1, signifying the presence of Cd-Te bond in the deposited thin film. The comprehensive evaluation of scanning electron micrographs emphasized the firm adhesion of the film to the substrate and displayed a uniform overlay of microstructures resembling rods. The observations from atomic force microscopy unveiled uniform grain structure with topographical features of hills and valleys. The UV-Visible spectroscopic examination elucidated that the as-deposited thin films exhibits a direct optical bandgap value of 1⋅59 eV. Temperature-dependent analysis of d.c. electrical resistivity exhibited a descending pattern, substantiating thin film's semiconducting attributes. The investigation into the photoresponse attributes of the thin film is accomplished by subjecting it to a polychromatic light, green and red monochromatic light source with an intensity of 50 mW/cm² employing three different biasing voltages. The thin film demonstrated maximum photocurrent for red light source than polychromatic and green light with maximum responsivity of 59⋅4 μA/W and detectivity of 17⋅7 × 106 Jones. These findings provide valuable insights on the photoresponse behavior of CBD deposited CdTe thin film in its as-deposited form.

Ferroelectric polycrystalline Bi2SiO5 thin films on Pt-covered Si substrates prepared by pulsed laser deposition combined with post-annealing

In this study, we report on the fabrication of polycrystalline thin film Bi2SiO5, a notable non-perovskite ferroelectric material. The thin films were deposited on Pt-covered Si substrates by pulsed laser deposition (PLD) at room temperature, followed by a post-annealing process in air. The as-deposited thin film was of an amorphous phase of Bi-Si-O, and turned to a polycrystalline phase of Bi2SiO5 by the post-annealing above 550°C. The influences of the post-annealing temperature on the phase preference, surface morphology, and dielectric properties of the thin films were investigated by Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), and dielectric measurements. As a result, the optimal post-annealing temperature was determined to be 600°C, yielding a good ferroelectric polycrystalline Bi2SiO5 thin film with a relative dielectric constant of 143 and a remanent polarization (2Pr) of 7.2 μC cm−2.

INVESTIGATION THE IMPACT OF DIFFERENT ANNEALING TEMPERATURES ON STRUCTURAL AND OPTICAL PROPERTIES OF BI-DOPED GETE (BI: 5 %) THIN FILMS FABRICATED BY PVD TECHNIQUE)

The impact of different annealing temperatures on the Bi-doped GeTe thin films were investigated. The thin films have been prepared by using physical vapor deposition techniques (PVD). The Bismuth (Bi) is doped GeTe with ratio of 5%. Different characterizations techniques have been used to study the different properties of thin films with several annealing temperatures. It has been found that the film thickness decreases as the annealing temperature increases. The XRD patterns show that as-deposited and annealed Bi-doped GeTe films at 150°C,200°C, and 250°C were fully amorphous, while the film annealed at 100 °C was crystalline. FESEM image shows that the structure is amorphous with no grain appearing for the crystallite GeTe compound. Whereas the annealed thin films at 100°C are well-appeared crystallites of GeTe with an average size of (110.64 nm). The thin films are annealed at (150, 200, and 250)°C which reveals that the crystallite or grain is increased. An increase in the annealing temperature has been found to cause a significant shift in the absorption edge toward an extended wavelength and an overall reduction in transmittance. At a wavelength of 1100 nm, the transmittance dropped from 65.25% for as-deposited thin films to 32.57% for annealed thin films at 250 °C. Furthermore, when the annealing temperature rises from 100°C to 250°C, the optical band gap reduces from 0.95 eV to 0.42 eV.

High-throughput synthesis and oxidation behavior of a continuous composition spread (Nb–Ti)1-x-ySixCry alloy thin film

High-throughput method of three targets magnetron sputter co-deposition was adopted to prepare (Nb–Ti)1-x-ySixCry composition spread alloy film (CSAF). Early oxidation behavior of the as-deposited alloy thin film was investigated in atmospheric conditions at 1250 °C for 10 min. A (Nb–Ti)1-x-ySixCry combinatorial material library covering (9.34–32.31) Si-(10.43–20.27) Cr (at. %) is obtained and as-deposited film was composed of amorphous phase. The oxidized film was separated into three regions having different oxidation products. The composition range for establishment of a protective scale (SiO2 and CrNbO4) and a small amount of Nb2O5 was ascertained efficiently across the entire alloy thin film.

Chemical characteristics via quantitative photoelectron analysis of chemical-solution-deposited yttrium oxide thin films for metal-insulator-metal capacitor applications

A cost-effective chemical bath deposition coupled with an annealing methodology is presented for obtaining yttrium oxide (Y2O3) thin films. The resultant thin films are homogeneous, free of pinholes, and show a relatively low surface roughness. The detailed characterization of the as-deposited thin film and the determination of optical, structural, and chemical characteristics of the films upon thermal transformation at 500 °C for 2 h was done with thermogravimetric analysis, X-ray diffraction, UV–Vis spectroscopy, surface topology analysis, and X-ray photoelectron spectroscopy. The results reveal that the as-deposited thin film is composed of an amorphous YOOH compound intrinsic to the synthesis process. However, with annealing, it is crystallized and transformed into a Y2O3 thin film showing a high optical transparency. The characteristics of the film are found to be influenced by the Y‒OH and Y‒O content with direct influence on the shape of the photoelectron spectra of the thin films showing a binding energy downshift of 1.6 eV from the 158.84 eV peak position found for the YOOH sample after annealing. The estimated surface roughness for the as-deposited YOOH and annealed Y2O3 samples resulted in 2.7 and 3.8 nm, respectively. The electrical characteristics and potential performance as a dielectric layer have been assessed in a Metal-Insulator-Metal configuration, where the acceptable values for leakage current in the 6 × 10−4 − 3 × 10−6 A/cm2 range and a capacitance of 218 and 80 nF/cm2 were measured for the YOOH and Y2O3 thin films, respectively. The latter indicates that these films are suitable candidates for gate dielectric transistor applications with the advantage of them being films produced via an economical and technically simple scalable process.

Augmentation of room temperature gas sensing properties of PANI thin films by 100 keV Ar+ ion irradiation

Polyaniline thin films were subjected to irradiation with Ar+ ions at four different concentrations: 1 × 1014, 1 × 1015, 1 × 1016, and 3 × 1016 ions/cm2, with an energy of 100 keV to improve the sensing ability. Field emission scanning electron microscope (FESEM) images revealed that the porosity as well as surface area of thin films increase significantly with the increase in fluence dose. The bandgap energy of the irradiated thin films found to decrease from 3.04 to 2.36 eV, whereas, the number of carbon atoms per cluster are found to increase from 127 to 211 atoms with increasing the Ar+ ions dose from 1x1014 to 3x1016 ions/cm2. The ratios of the areas under the curves AQ/AB are increased from 0.221 to 0.456 as the Ar+ ion fluence dose rate rose from 0 to 3 × 1016 ions/cm2. Thus, it can be assumed that the electrical conductivity of the PANI films increase with the Ar+ ion fluence dose rate via carbonaceous clustering, and the scission of polymer chains. The as-deposited PANI thin film demonstrated the lowest sensing response at approximately 33 %, while the thin film irradiated with the highest dose of 3 × 1016 ions/cm2 exhibited the highest sensing response at around 1119 % for methanol vapors at a concentration of 100 ppm.

Surface oxide ion conduction of BaCe0.5Pr0.3Y0.2O3−δ thin film with complex mixed valence states

Solid oxide fuel cells (SOFCs), which operate in the medium temperature range from 300 °C to 500 °C, are effective in shortening startup time and reducing fuel gas. In order to realize a practical electrolyte with high oxide ion conductivity, we have investigated the ionic conductivity of c-axis oriented BaCe0.5Pr0.3Y0.2O3−δ (BCPY) thin films with complex mixed valence states prepared on Al2O3 (0001) substrates by RF magnetron sputtering. The amount of oxygen vacancies on the surface in the as-deposited BCPY thin film was evaluated to be ∼6.7% by X-ray absorption spectroscopy and defect chemical analysis. The as-deposited film exhibited relatively high ionic conductivity (σT) of more than 10−1 S·K cm−1 and activation energy (E A) of ∼0.57 eV in the medium temperature range by thermal activation process on the surface. The energy separation between the top of the VB and the Fermi level was much larger than E A, indicating that the BCPY thin film is a pure oxide ion conductor without the contribution of electron or hole carriers. These results indicate that the c-axis oriented BCPY thin film can be applied to electrolyte of SOFC operating in the medium temperature range.