Transparent conductive In2O3:Mo thin films prepared by reactive direct current magnetron sputtering at room temperature

An amorphous transparent conductive oxide thin film of molybdenum-doped indium oxide (IMO) was prepared by reactive direct current magnetron sputtering at room temperature. The films formed on glass microscope slides show good electrical and optical properties: the low resistivity of 5.9 × 10^− 4 Ω cm, the carrier concentration of 5.2 × 10²⁰ cm^− 3, the carrier mobility of 20.2 cm² V^− 1 s^− 1, and an average visible transmittance of about 90.1%. The investigation reveals that oxygen content influences greatly the carrier concentration and then the photoelectrical properties of the films. Atomic force microscope evaluation shows that the IMO film with uniform particle size and smooth surface in terms of root mean square of 0.8 nm was obtained.     

Electrical, optical, and structural properties of InZnSnO electrode films grown by unbalanced radio frequency magnetron sputtering

We have investigated the electrical, optical, structural, and annealing properties of indium zinc tin oxide (IZTO) films prepared by an unbalanced radio frequency (RF) magnetron sputtering at room temperature, in a pure Ar ambient environment. It was found that the electrical and optical properties of unbalanced RF sputter grown IZTO films at room temperature were influenced by RF power and working pressure. At optimized growth condition, we could obtain the IZTO film with the low resistivity of 3.77 × 10^− 4 Ω cm, high transparency of ~ 87% and figure of merit value of 21.2 × 10^− 3Ω^− 1, without the post annealing process, even though it was completely an amorphous structure due to low substrate temperature. In addition, the field emission scanning electron microscope analysis results showed that all IZTO films are amorphous structures with very smooth surfaces regardless of the RF power and working pressure. However, the rapid thermal annealing process above the temperature of 400 °C lead to an abrupt increase in resistivity and sheet resistance due to the transition of film structure from amorphous to crystalline, which was confirmed by X-ray diffraction examination.     

Densification of In2O3:Sn multilayered films elaborated by the dip-coating sol-gel route

Indium Tin Oxide (ITO) thin films have been deposited by the Sol-Gel Dip-Coating technique, the starting solutions being prepared from chlorides. These multilayered films were crystallized by means of a classical heat treatment at temperatures ranging from 500 to 600 °C. Five stacked layers are necessary to obtain a global electrical resistivity value of 2.9×10⁻³ Ω cm, for 500 °C annealed film. The paper focuses on the study of the structure of such multilayered deposits, and on the densification process, using transmission electron microscopy, Rutherford Back-scattering Spectrometry and electrical resistivity measurements. This analysis reveals structural inhomogeneities and different crystallite growth processes as a function of annealing temperature and number of deposited layers.     

Investigation of the growth of In2O3 on Y-stabilized ZrO2(100) by oxygen plasma assisted molecular beam epitaxy

Thin films of In₂O₃ have been grown on Y-stabilised ZrO₂(100) substrates by oxygen plasma assisted molecular beam epitaxy over a range of substrate temperatures between 650 °C and 900 °C. Growth at 650 °C leads to continuous but granular films and complete extinction of substrate core level structure in X-ray photoelectron spectroscopy. However with increasing substrate temperature the films break up into a series of discrete micrometer sized islands. Both the continuous and the island films have excellent epitaxial relationship with the substrate as gauged by X-ray diffraction and selected area electron diffraction and lattice imaging in high resolution transmission electron microscopy.     

Study on In2O3-SnO2 transparent and conductive films prepared by d.c. sputtering using high density ceramic targets

The influence of SnO₂ concentration in the target on the film characteristics was studied in order to make the useful database for the device design when low discharge voltage sputtering method and a high density In₂O₃-SnO₂ ceramic targets were used. In the case of the films deposited on unheated substrate, X-ray diffraction profile showed amorphous structure. Minimum resistivity of 358 μΩ cm was obtained by In₂O₃ film with mobility of 40.1 cm² (V s)⁻¹ and carrier density of 4.35E+20 cm⁻³. With the increase of SnO₂ contents, resistivity of the films increased because of the decrease in both carrier density and mobility. Whereas, the films deposited on heated substrates showed polycrystalline structure. Resistivity was reduced, ranging from 5 to 20 wt.% SnO₂, and minimum resistivity of 136 μΩ cm was obtained at 15 wt.% with mobility of 40.5 cm² (V s)⁻¹ and carrier density of 1.13E+21 cm⁻³. Transmittance and reflectance of these films strongly depend on carrier density.     

Synthesis and structural characterization of mesoporous V2O5 thin films for electrochromic applications

Mesoporous vanadium pentoxide (V₂O₅) films have been synthesized by hydrolysis of vanadium tri-isopropoxide (VO(OC₃H₇)₃) in the presence of polyethylene glycol (PEG) as a structure-directing agent. The structure, the stoichiometry and the morphology of the films have been studied as a function of the thermal annealing by X-ray diffraction (XRD), micro-Raman spectroscopy, optical microscopy, scanning electron microscopy and atomic force microscopy. XRD patterns and Raman spectra show the presence of two previously unreported crystalline phases. The PEG:V₂O₅ molar ratio affects the temperature of phase formation, the amount and even the order in which the phases appear. The morphological characterization underlines the role of the surfactant to promote porous networks, formed by micrometric clusters of controlled shapes and patterns embedded in a homogeneous host matrix.     

Electronic structural analysis of transparent In2O3-ZnO films by hard X-ray photoelectron spectroscopy

The electronic structural analysis of the conductive transparent films was carried out using bulk sensitive hard X-ray photoelectron spectroscopy (HAXPES). The In₂O₃-ZnO film has amorphous structure before and after annealed, and the conduction band spectrum around Fermi level showed the similar spectra with that of as-deposited amorphous In₂O₃ film. In these amorphous films, the conduction band minimum locates at the deeper level than the crystalline In₂O₃ film. The electronic state which comes from randomness of amorphous structure possibly exists around this level or below. These electrons are expected to act as scattering center. We concluded that the electron mobility depends on the density of this electronic state.     

In2O3 films prepared by thermal oxidation of amorphous InSe thin films

In₂O₃ thin films were prepared by the thermal oxidation of amorphous InSe films in air atmosphere. The structure, morphology and composition of the thermal annealed products were characterized by X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive spectroscopy, respectively. The XRD patterns indicate that the as-deposited InSe films were amorphous and they fully transformed into polycrystalline In₂O₃ films with a cubic crystal structure in the preferential (222) orientation at a temperature around 600 °C. The optical energy gap of 3.66 eV was determined at room temperature by transmittance and reflectance measurements using UV-vis-NIR spectroscopy. A preliminary characterization shows that these films have a promising response towards NO₂ gas at a working temperature around 180 °C.     

Synthesis of (Na2O,PbO)-Nb2O5, (Na2O,BaO)-Nb2O5, and (K2O,SrO)-Nb2O5 thin films using sol-gel method

Homogeneous pore-free Ba₂NaNb₅O₁₅, KSr₂Nb₅O₁₅, and 2·Na₂O-PbO-6·Nb₂O₅ thin films were fabricated on sapphire substrates using the sol-gel technique. By controlling the gelation and coating process, thickness of thin films fabricated was controllable from ~ 40 nm to ~ 10 μm. Synthesized thin films possessed highly preferred orientated microstructure. Another advantage of this method is the subsequent heat treatment temperature dramatically decreased compared with other methods. This increases stoichiometry control and makes the large scale fabrication more feasible and efficient.     

Physical properties of flash evaporated In2O3 films prepared at different substrate temperatures

Indium oxide (In₂O₃) thin films were prepared by flash evaporated technique under various substrate temperatures in the range of 303-673 K and systematically studied the structural, electrical and optical properties of the deposited films. The films formed at substrate temperatures of < 373 K were amorphous while those deposited at higher substrate temperatures (≥ 373 K) were polycrystalline in nature. The optical band gap of the films decreased from 3.71 eV to 2.86 eV with the increase of substrate temperature from 303 K to 673 K. Figure of merit of the films increased from 2.8 × 10³ Ω^− 1 cm^− 1 to 4.2 × 10³ Ω^− 1 cm^− 1 with increasing substrate temperature from 303 K to 573 K, thereafter decreased to 2.2 × 10³ Ω^− 1 cm^− 1 at higher temperature of 673 K.     

New LaCu0.5Mn0.5O3 thin films deposited by the sol-gel process on different substrates

New LaCu_0.5Mn_0.5O₃ thin films deposited by the sol-gel process on ceramic Al₂O₃ and ZrO₂, glass ceramic and 101 single-crystal quartz, using the sol-gel process. It was found in all cases that the films are polycrystalline and single phase without preferred orientation. The morphology of the films depends strongly on the nature of the substrate. The films deposited on Al₂O₃ exhibit morphological characteristics making them suitable as possible sensors and catalysts.     

Epitaxial growth of Cr2O3 thin film on Al2O3 (0001) substrate by radio frequency magnetron sputtering combined with rapid-thermal annealing

We prepared epitaxially grown Cr₂O₃ thin films on Al₂O₃ (0001) substrate by using radio frequency magnetron sputtering at room temperature followed by a rapid-thermal annealing process. It is shown that the phase and the crystallinity of as-grown samples depend on the flow ratios of the working gas (Ar/O₂). X-ray diffraction (XRD) results show that oxygen-rich CrO₃ phase having preferred orientation is formed when sputter-grown at room temperature under the working gas (Ar/O₂) flow ratios of 9:1 and 7:3. XRD Φ-scanning results exhibit that annealing causes the oxygen-rich CrO₃ phase to transform into epitaxial Cr₂O₃ phase, which is confirmed by X-ray photoemission spectroscopy. The samples grown at the gas flow ratio of 9:1 exhibit very smooth surfaces with root mean square roughness of 0.1-0.3 nm.     

Charge trapping characteristics of Al2O3/Al-rich Al2O3/SiO2 stacked films fabricated by radio-frequency magnetron co-sputtering

A thin-film structure comprising Al₂O₃/Al-rich Al₂O₃/SiO₂ was fabricated on Si substrate. We used radio-frequency magnetron co-sputtering with Al metal plates set on an Al₂O₃ target to fabricate the Al-rich Al₂O₃ thin film, which is used as a charge storage layer for nonvolatile Al₂O₃ memory. We investigated the charge trapping characteristics of the film. When the applied voltage between the gate and the substrate is increased, the hysteresis window of capacitance-voltage (C-V) characteristics becomes larger, which is caused by the charge trapping in the film. For a fabricated Al-O capacitor structure, we clarified experimentally that the maximum capacitance in the C-V hysteresis agrees well with the series capacitance of insulators and that the minimum capacitance agrees well with the series capacitance of the semiconductor depletion layer and stacked insulator. When the Al content in the Al-rich Al₂O₃ is increased, a large charge trap density is obtained. When the Al content in the Al-O is changed from 40 to 58%, the charge trap density increases from 0 to 18 × 10¹⁸ cm^− 3, which is 2.6 times larger than that of the trap memory using SiN as the charge storage layer. The device structure would be promising for low-cost nonvolatile memory.     

Investigations on TlBa2Ca2Cu3Ox superconducting thin films formation on LaAlO3 substrate

Investigations on pure superconducting phase TlBa₂Ca₂Cu₃O_x (Tl-1223) thin films formation, of about 100-125 nm in thickness, on (001) LaAlO₃ single crystal substrate, were made using radio-frequency sputtering deposition of Ba₂Ca₂Cu₃O_x precursor films and ex-situ thallination in sealed quartz tube. The precursor films were thallinated under different conditions of partial oxygen pressure, temperature, time and y thallium source content using unreacted pellets of composition Tl_yBa₂Ca₂Cu₃O_x. In all cases, strongly c-oriented multiphase films were obtained. A correlation between the Tl-1223 phase purity and the precursor film conditions of thallination is established. Temperature and time of thallination as well as the thallium source content and the partial pressure of oxygen play a key role in the quality of the obtained film. The films' onset temperature of the superconducting transition ranges between 90 and 103 K. It is shown that the best samples can be obtained from a dense precursor film and relatively medium thallination time.     

Gas sensing characteristics of WO3 nanoplates prepared by acidification method

WO₃⋅ H₂O nanoplates were prepared by the acidification of Na₂WO₄? 2H₂O and converted into monoclinic WO₃ nanoplates by heat treatment. The sizes, morphologies and preferred orientation of the WO₃ nanoplates could be controlled by manipulating the acidity of the solution used for the acidification reaction. All of the WO₃ nanoplates showed the selective detection of NO₂ in the presence of other reducing gases, such as C₂H₅OH, CH₃COCH₃, CO, C₃H₈, and H₂. The gas response, selectivity, and response speed were optimized by varying the morphology of the sensing materials and operation temperature. The WO₃ nanoplates with a mean edge size of 192 nm showed the most rapid gas response along with a high response and selectivity to NO₂ when operated at 300 °C.     

Band offset of the In2S3/indium tin oxide interface measured by X-ray photoelectron spectroscopy

In₂S₃ thin films have been grown on Indium Tin Oxide (ITO) by Chemical Spray Pyrolysis. The structural and physical-chemical properties of the films have been investigated by means of X-ray Diffraction and X-ray Photoelectron spectroscopy (XPS). The valence band discontinuity at the In₂S₃/ITO interface has been determined by XPS resulting in a value of 1.9 ± 0.2 eV. Consequently, the conduction band offset has been estimated to be 1.0 ± 0.4 eV.     

Intrinsic room temperature ferromagnetism in Zn0.92Co0.08O thin films prepared by pulsed laser deposition

Zn_0.92Co_0.08O thin films were fabricated on p-type Si (100) and quartz substrates by pulsed laser deposition using a ZnCoO ceramic target. The structural and magnetic properties of the films were characterized by field emission scan electronic microscopy, x-ray diffraction, x-ray photoemission spectroscopy, UV-visible transmission spectra, extended x-ray absorption fine structure spectroscopy and physical property measurement system. Substitutional doping of Co²⁺ in ZnO lattice is demonstrated in the films. The as-deposited Zn_0.92Co_0.08O thin film displayed intrinsic room temperature ferromagnetism with saturation magnetization (M_s) of ~ 0.20μ_B/Co. The corresponding M_s increased to ~ 0.23μ_B/Co when annealed in vacuum and further to ~ 0.42μ_B/Co after annealed in hydrogen. In turn, the M_s dropped to the value of ~ 0.13μ_B/Co after annealed in oxygen. Our studies indicate that oxygen vacancy density plays a key role in mediating the ferromagnetism of the diluted magnetic semiconductor films.     

Overview of optical properties of Al2O3 films prepared by various techniques

We study optical properties of Al₂O₃ films prepared by various techniques using spectroscopic ellipsometry. The film preparation techniques include conventional pulsed magnetron sputtering in various gas mixtures, high power impulse magnetron sputtering, annealing of as-deposited Al₂O₃ in an inert atmosphere and annealing of as-deposited Al in air. We focus on the effect of the preparation technique, deposition parameters and annealing temperature on the refractive index, n, and extinction coefficient, k, of stoichiometric Al₂O₃. At a wavelength of 550 nm we find n of 1.50-1.67 for amorphous deposited Al₂O₃, 1.65-1.67 for amorphous Al₂O₃ obtained by Al annealing, 1.46-1.69 for γ-Al₂O₃ and decreasing n for Al₂O₃ annealing temperature increasing up to 890 °C. The results facilitate correct interpretation of optical characterization of Al₂O₃, as well as selection of a preparation technique corresponding to a required Al₂O₃ structure and properties.     

A hexane solution deposition of SnS2 films from tetrabutyltin via a solvothermal route at moderate temperature

SnS₂ films have been deposited on glass and alumina plate substrates by the reactions between an organotin precursor [tetrabuyltin, (CH₂CH₂CH₂CH₃)₄Sn] and carbon disulfide in n-hexane at the temperature range 180-200 °C for 10-40 h. The reaction system was oxygen free and applied at a moderate temperature. The films so prepared were characterized by techniques of X-ray diffraction, Scanning electron microscopy, Raman and Mössbauer spectroscopies. The films deposited on glass as well as on alumina plate have an average thickness of 30 μm, but have different rose-like morphologies, which are influenced by both the anisotropic growths of crystals and the different substrate structures. Photoluminescence measurements show that the films have an emission peak at approximately 590 nm.     

Atomic layer deposition growth of zirconium doped In2O3 films

Zirconium doped indium oxide thin films were deposited by the atomic layer deposition technique at 500 °C using InCl₃, ZrCl₄ and water as precursors. The films were characterised by X-ray diffraction, energy dispersive X-ray analysis and by optical and electrical measurements. The films had polycrystalline In₂O₃ structure. High transparency and resistivity of 3.7×10⁻⁴ Ω cm were obtained.