Indium Oxide Films Research Articles

Synthesis and characterization of transparent optical gas sensor device made of indium oxide pyramid like nanoarchitectures

Gas sensors are of paramount concern for medical, industrial, environmental, and domestic applications. There are two substantial frameworks to monitor the gases either by physical or chemical methods. Recently, optical gas sensing method has been employed for detection of gases because it offers fast response, high selectivity and minimal drift. Herein, highly transparent and single crystalline indium oxide film is prepared by using hexamethylene triperoxide diamine for the first time. The prepared film was characterized through X-ray diffraction, scanning and transmission electron microscopies. It was found that the indium oxide film has a body center cubic structure and has single crystalline phase. The formed nanoparticles were pyramid like shape with dimensions 26nm×16nm×18nm. The film has high transparency (95%) and strong luminescence emission intensity in the UV region. The prepared indium oxide film showed fast, accurate and highly stable gas detection. The optical band gap of the prepared film strongly depends on the type of tested gas. The oxidizing gases caused a blue shift of the luminescence peak and the reducing gases caused a red shift and each gas showed an emission luminescence peak at a certain wavelength. Among all tested gases, the indium oxide film with pyramid like shape was highly sensitive to carbon monoxide along the concentration range from 0 to 100ppm.

Paper No P19: Aluminum Nanostructured Coatings as Alternatives to Metal Oxide and Transparent Semiconductors

AbstractAl nanostructured coatings are the promising alternative to a tin‐doped indium oxide film (ITO) as transparent conductive electrodes. In this paper, we describe the fabrication of Al nanostructured coatings by electrochemical anodization of aluminum deposited by magnetron sputtering on a glass substrate. The process of anodization is strictly controlled by the characteristic changes of process parameters, followed by selective chemical etching of aluminum oxide. We proposed the model for Al nanostructured coatings describing the dependences of their optical transmittance and surface resistance on the characteristic dimensions of the network structure.

Detecting DNA-DNA Hybridization at 3-Mercaptopropionic Acid Self-Assembled on Tin-Doped Indium Oxide Film with Electrochemical Measurement

Self-assembled monolayers (SAM) of 3-mercaptopropionic acid (MPA) were applied on tin-doped indium oxide (ITO) surfaces and used as a working electrode for sensing DNA hybridization. The concentration of probe single stranded DNA (ssDNA), complemented with target DNA, was optimized for the highest yield immobilization on MPA/ITO platform. The ssDNA/MPA/ITO was allowed to hybridize to target DNA prepared from PCR amplification that first tested by the synthesized complementary sequences. Both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were employed for investigating probe ssDNA immobilization and target DNA hybridization. For fast and low concentration detecting purposes, methylene blue (MB) coupled with differential pulse voltammetry (DPV) was used for detecting the target DNA hybridization events.

Preparation and characterization of single crystalline In2O3 films deposited on MgO (110) substrates by MOCVD

Epitaxial indium oxide (In2O3) films have been prepared on MgO (110) substrates by metal-organic chemical vapor deposition (MOCVD). The deposition temperature varies from 500°C to 700°C. The films deposited at each temperature display a cube-on-cube orientation relation with respect to the substrate. The In2O3 film deposited at 600°C exhibits the best crystalline quality. A clear epitaxial relationship of In2O3 (110)|MgO (110) with In2O3 [001]|MgO [001] has been observed from the interface area between the film and the substrate. The average transmittance of the prepared films in the visible range is over 95%. The band gap of the obtained In2O3 films is about 3.55–3.70eV.

The effect of oxygen ion beam bombardment on the properties of tin indium oxide/polyethylene terephthalate complex

The tin indium oxide (ITO) films were deposited onto the polyethylene terephthalate (PET) surface that has been bombarded by an O ion beam. The variation of the O bombardment time resulted in the production of ITO/PET complex with different properties. Characterization by four-point probe measurement after the bending fatigue test showed that the adhesion property of the ITO/PET complex could be improved by the increase of O bombardment time while little change of electrical resistivity was observed. Scanning electron microscopy results showed that after the bending fatigue test, the nano scale seams and micro scale trenches appeared at the surface of the ITO/PET complex. The former was only the cracks of ITO film, which has little influence on the continuity and electrical resistivity of ITO film. On the contrary, the micro scale trenches were caused by the peeling off of ITO chips at the cracks, which mainly influenced the continuity and electrical resistivity of ITO film. With the increase of O bombardment time, the number and length of the micro scale trenches decreased. X-ray photoelectron spectrometry characterization showed that with the increase of O bombardment time, parts of the methylene C bonds were transformed into CO bonds, which could be broken to form COIn(Sn) bonds at the initial stage of ITO film growth. By these COIn(Sn) crosslink bonds, the ITO film could adhere well onto the PET and the ITO/PET complex display better anti-bending fatigue property. Finally, in the context of the application of the ITO/PET complex as a flexible electrode substrate, the present work reveals a simple way to crosslink them, as well as the physicochemical mechanism happening at the interface of complex.

Mo-doped indium oxide films by dip-coating: Synthesis, microstructure and optical properties

Molybdenum doped indium oxide (In2−xMoxO3, IMO) is widely used in many electronic and optoelectronic devices due to its excellent electrical properties and optical transparency. In this work, a first attempt to produce IMO films by sol–gel dip coating was reported, starting from different reagents (i.e. indium nitrate or indium chloride and molybdenum chloride or ammonium molybdate as In and Mo sources, respectively). The influence of different reagents, solvents and annealing atmospheres (i.e. air and N2) on final coating properties was investigated in order to properly select the optimal process parameters. The morphological, microstructural and optical properties of the produced coatings were evaluated by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and UV–vis spectroscopy. The best performances, in terms of microstructure and transparency, were obtained for films produced by dip coating the indium nitrate and molybdenum chloride based solutions (In nitrate concentration 0.1–0.2 M), with the addition of a low amount of PEG, followed by annealing at 500 °C. The produced coatings consisted of monophasic In2O3 and were characterised by a uniform, homogeneous and cracks free surface, and high transmittance values in the vis range (i.e. 85–98%).

Electrostatic tuning of the properties of disordered indium-oxide films near the superconductor-insulator transition

The evolution with carrier concentration of the electrical properties of amorphous indium oxide (InO) thin films has been studied using electronic double layer transistor configurations. Carrier variations of up to 7 X 10^(14) carriers/cm^2 were achieved using an ionic liquid as a gate dielectric. The superconductor-insulator transition was traversed and the magnitude and position of the large magnetoresistance peak found in the insulating regime were modified. The systematic variation of the magnetoresistance peak with charge concentration was found to be qualitatively consistent with a simulation based on a model involving granularity.

Study on the growth mechanism of tin-doped indium oxide films deposited by direct current pulse magnetron sputtering

Tin-doped indium oxide (ITO) films were deposited on Si(100) and glass substrates at different deposition time by direct current pulse magnetron sputtering. The step profiler, four-point probe measurements and atomic force microscopy were used to study the thickness, sheet resistance, as well as the nucleation and growth behavior of ITO films, respectively. The dynamic scaling of roughness evolution could be divided into three stages, which are the growth of islands, the coalescence of islands, and the homogeneous growth, respectively. Compared with the glass substrate, it needs long time to nucleate on Si(100) substrate for fewer defects on the surface. Base on the result above, the mechanisms of defect nucleation and islands coalescence could be given.

Crossover from weak localization to anti-weak localization in indium oxide systems with wide range of resistivity

We investigated the magnetoconductivity Δσ(H)≡1/ρ(H)−1/ρ(0) in a wide range of magnetic fields for three-dimensional indium oxide films doped with zinc, tin, or gallium in the range of resistivity ρ(300K) between 4.1×10−6 Ωm and 1.7×10−3 Ωm. The weak localization theory was fitted to data for Δσ(H) at various temperatures in the range 2.0 K≤T≤50 K by the use of suitable characteristics Dτin(T) and Dτso, where D, τin, and τso are the electron diffusion constant, inelastic scattering time, and spin-orbit (s-o) scattering time, respectively. It was found that (i) for films with a large value of ρ, the sign of Δσ(H) changes from positive to negative with decreasing temperature as a precursor to an anti-weak localization effect; (ii) the ratio τso/τin decreases from ≈4000 to≈4.0 with increasing ρ; (iii) the strong ρ dependence of Dτso cannot be explained by the model with a constant atomic number Z in a formula τso∝1/Z4 proposed by Abrikozov and Gorkov Zh. Eksp. Teor. Fiz. 42, 1088 (1962); [Sov. Phys. JETP 15, 752 (1962)]. As a reason for this ρ dependence, we suggest that the s-o scattering changes with increasing ρ from light oxygen atoms to heavy atoms, i.e., indium, zinc, and gallium, because of the decrease in the number of oxygen vacancies acting as s-o scattering centers.

Spray Deposited Thin Films of Tin-Doped Indium Oxide for Optoelectronic Applications

The structural, electrical, and optical properties of spray deposited tin-doped indium oxide (ITO) films are reported in this work. The films have excellent properties, as a transparent and conducting electrode, for applications in a wide range of areas of optoelectronics such as photodetection and photovoltaic. One example of the ITO thin films application in semiconductor-insulating-semiconductor (SIS) efficient solar cells and modules is shown.

Polycrystalline indium phosphide on silicon using a simple chemical route

We describe a simple, aqueous and low thermal budget process for deposition of polycrystalline indium phosphide on silicon substrate. Using stoichiometric indium oxide films prepared from its spin-coated precursor on silicon as an intermediate step, we achieve stoichiometric indium phosphide films through phosphidisation. Both indium oxide and indium phosphide have been characterized for surface morphology, chemical composition, and crystallinity. The morphology and crystalline structure of the films have been explained in terms of the process steps involved in our deposition method. Incomplete phosphidisation of indium oxide to indium phosphide results in the restructuring of the partly unconverted oxide at the phosphidisation temperature. The optical properties of the indium phosphide films have been analyzed using micro photoluminescence and the results compared with those of a homoepitaxial layer and a theoretical model. The results indicate that good optical quality polycrystalline indium phosphide has been achieved. The Hall measurements indicate that the carrier mobilities of our samples are among the best available in the literature. Although this paper presents the results of indium phosphide deposition on silicon substrate, the method that we present is generic and can be used for deposition on any suitable substrate that is flexible and cheap which makes it attractive as a batch process for photovoltaic applications.

Optimization of the deposition and annealing conditions of fluorine-doped indium oxide films for silicon solar cells

Fluorine-doped indium oxide (IFO) films are deposited onto (pp+)Si and (n+nn+)Si structures made of single-crystal silicon by ultrasonic spray pyrolysis. The effect of the IFO deposition time and annealing time in an argon atmosphere with methanol vapor on the IFO chemical composition, the photovoltage and fill factor of the Illumination-Uoc curves of IFO/(pp+)Si structures, and the sheet resistance of IFO/(n+nn+)Si structures, correlating with the IFO/(n+)Si contact resistance, is studied. The obtained features are explained by modification of the properties of the SiOx transition layer at the IFO/Si interface during deposition and annealing. Analysis of the results made it possible to optimize the fabrication conditions of solar cells based on IFO/(pp+)Si heterostructures and to increase their efficiency from 17% to a record 17.8%.

Investigation of magnetism in Fe and Cu ion implanted indium oxide films

Diluted magnetic semiconductor based on indium oxide has been prepared by transition metal ion implantation. Fe and Cu ions have been implanted into pulsed laser deposition prepared pure In2O3 films by metal vapor vacuum arc source with doses from 5×1015cm−2 to 1×1017cm−2, respectively. The implanted samples are annealed in the air subsequently. The structure of In2O3 films is characterized by X-ray diffraction. X-ray photoelectron spectroscopy measurements are applied to confirm the electronic state of the implanted ions. Superconducting quantum interference device measurements at room temperature disclose that the diamagnetic In2O3 films turned to be ferromagnetic after Fe and Cu ion implantation. The correlation between ferromagnetism and implantation conditions is tested. The ferromagnetism is attributed to the bound magnetic polarons formed by Fe, Cu ion implantation.

High quality of IWO films prepared at room temperature by reactive plasma deposition for photovoltaic devices

High-quality tungsten-doped indium oxide (IWO) films are deposited on glass substrates at room temperature by the reactive plasma deposition (RPD) process under different oxygen/argon (O2/Ar) ratios. It is revealed that the O2/Ar ratio plays an important role in obtaining high conductivity without compromising the optical transmission of the films. The effect of the annealing temperature on the structure, electrical and optical properties of IWO thin films is investigated. The as-deposited film is crystalline and then re-crystallizes by postannealing. In this work, the IWO film with the O2/Ar ratio of 14% annealed at 220 °C exhibits the best electrical conductivity, with a lowest resistivity of 3.34 × 10−4 Ω cm and a highest mobility of 77.8 cm2 V−1 s−1, and which has the average transmittance of 85.50% (visible region) and 94.21% (near-infrared region). These optical and electrical characteristics of IWO films make them suitable for a-Si/C–Si heterojunction solar cell applications.

Structural and electrical properties of sputtering power and gas pressure on Ti-dope In2O3 transparent conductive films by RF magnetron sputtering

Transparent conductive titanium-doped indium oxide (ITiO) films were deposited on Corning glass substrates by RF magnetron sputtering method. The effects of RF sputtering power and Ar gas pressure on the structural and electrical properties of the films were investigated experimentally, using a 2.5wt% TiO2-doped In2O3 target. The deposition rate was in the range of around 20–60nm/min under the experimental conditions of 5–20mTorr of gas pressure and 220–350W of RF power. The lowest resistivity of 1.2×10−4Ωcm, the average optical transmittance of 75%, the high hall mobility of 47.03cm2/Vs and the relatively low carrier concentration of 1.15E+21cm−3 were obtained for the ITiO film, prepared at RF power of 300W and Ar gas pressure of 15mTorr. This resistivity of 1.2×10−4Ωcm is low enough as a transparent conducting layer in various electro-optical devices and it is comparable with that of ITO or ZnO:Al conducting layer.

Analysis of device parameters of Al/In2O3/p-Si Schottky diode

Thin film of indium oxide (In2O3) is deposited on p-silicon substrate using sol-gel spin technique. The sol-gel spin deposited film is very smooth with grain size and root mean square surface roughness of ~40nm and ~7.9nm, respectively. The device parameters of Al/In2O3/p-Si Schottky diode were investigated using direct current current-voltage (I-V) and impedance spectroscopy. The ideality factor and barrier height of the diode were determined to be 1.07+/-0.03 and 0.72+/-0.02eV, respectively. At higher voltages, the charge transport mechanism of the diode is controlled by a trap-charge limited conduction mechanism (TCLC). The series resistance profile of the diode was extracted to show the presence of the interface states changing with frequency.

Tunneling Density of States of Indium Oxide Films Through the Superconductor to Insulator Transition

We present planar tunneling junction spectroscopy measurements on disordered amorphous indium oxide films on both sides of the superconductor–insulator transition. Our measurements directly reveal a superconducting gap in the insulating phase. The measured energy gap has the same energy scale on both sides of the transition. Unlike the case of granular films, the tunneling curves cannot be fitted to the BCS density of state expression, even when introducing a broadening parameter to account for nonthermal broadening sources. The results are consistent with the presence of superconducting islands of which superconducting properties depend on film disorder and on the carrier density of the superconducting material.

Structural and Electrical Properties of Titanium-Doped Indium Oxide Films Deposited by RF Sputtering

Titanium-doped indium oxide (ITiO) is a high-quality transparent conducting oxide commonly used as the contact for photovoltaic. The transparent conductive titanium-doped indium oxide (ITiO) films were deposited on Corning glass substrates by RF magnetron sputtering method. The effects of RF sputtering power and Ar gas pressure on the structural and electrical properties of the films were investigated experimentally, using a 2.5 wt% TiO2 -doped In2O3 target. The deposition rate was in the range of around 20 to 60nm/min under the experimental conditions of the gas pressure and the RF Magnetron sputtering power. In this case, the lowest resistivity of 1.2×10-4-cm and the average optical transmittance of 75% were obtained for the ITiO film, prepared at RF power of 300W and Ar gas pressure of 15 mTorr. This resistivity of 1.2×10-4-cm is low enough as a transparent conducting layer in various electro-optical devices and it is comparable with that of ITO or ZnO:Al conducting layer.

Preparation of Titanium-doped Indium Oxide Films by Ultrasonic Spray Pyrolysis Method

Titanium-doped indium oxide (ITiO) films were deposited on soda-lime glass by ultrasonic spray pyrolysis. The optimum conditions of deposition parameters, such as dopant concentration for lowest resistivity were investigated. Phase formation and microstructure of the films were examined by XRD and SEM. AFM was used to obtain the surface topology of the prepared films. The optical transmission and resistivity of films were determined by UV-Vis-NIR spectrophotometer and Van der Pauw method respectively. The resistivity of films depended on the titanium content. The feasibility study of using the ITiO as one of the TCO for solar cell was discussed.

The Effect of Solvent on the Morphology of Indium Oxide Deposited by Aerosol-assisted Chemical Vapour Deposition

Aerosol-assisted chemical vapour deposition (AACVD) reactions of InMe3 and a mono-functional or donor-functional alcohol have been investigated and the resulting film morphology studied using scanning electron microscopy. AACVD of InMe3 and 6 equivalents of the donor-functionalized alcohol HOCH2CH2NMe2 in toluene resulted in the deposition of transparent indium oxide films, with a slight brown tinge, at 450°C. In contrast, AACVD of InMe3 and 6 equivalents of MeOH in toluene resulted in no film growth. However, use of methanol as both the solvent and oxygen source via AACVD of InMe3 in MeOH at a range of temperatures (350–500°C) afforded crystalline transparent indium oxide films. Similarly, AACVD of InMe3 and 6 equivalents of HOCH2CH2NMe2 in MeOH resulted in transparent indium oxide films with better substrate coverage. The indium oxide films were analyzed by a range of techniques including scanning electron microscopy, glancing-angle X-ray powder diffraction, UV-visible spectroscopy, and wavelength dispersive analysis of X-rays, which confirmed the formation of cubic In2O3 with band-gaps in the range 3.51–3.60 eV. Scanning electron microscopy showed a variation in film morphology and indicated that both temperature and the use of methanol influenced the resulting microstructure. Sheet resistance and Hall effect measurements indicate that the films deposited at 450°C are suitable candidates for transparent conducting oxide materials.