Indium Oxide Films Research Articles

Evaluation of Sn-Doped Indium Oxide Film and Interface Properties on a-Si Formed by Reactive Plasma Deposition

In pursuit for the improvement of heterojunction Si solar cell performance, we evaluated Sn-doped Indium oxide (ITO)/a-Si structure by using conventional and hard X-ray photoelectron spectroscopy (XPS, HAXPES) to identify the cause of solar cell performance degradation. HAXPES allows us to evaluate the SiOx layer at the ITO/a-Si interface non-destructively. The SiOx formation at the ITO/a-Si interface leads to an increase the contact resistance, which can be reduced by post deposition annealing (PDA). In addition, PDA promoted the evaluation of Fermi level, the precipitation of ITO component in a-Si layer, and the increase of interface roughness. Before PDA, the diffusion of Sn atoms in a-Si was observed. Furthermore, it was also confirmed by PDA that Si atoms were diffused to ITO. These reaction at the ITO/a-Si interface may be part of the degradation factor of the Si solar cells.

Atomic layer deposition of ultrathin indium oxide and indium tin oxide films using a trimethylindium, tetrakis(dimethylamino)tin, and ozone precursor system

Indium oxide (IO) and indium tin oxide (ITO) are widely used in optoelectronics applications as a high quality transparent conducting oxide layer. A potential application of these coatings is for enhancing the electrical properties of spacecraft thermal radiator coatings, where dissipating built-up static charge is crucial. In this work, the authors investigated the thickness-dependent electrical and optical properties of IO thin films synthesized by atomic layer deposition (ALD) with the aim of finding the optimum condition for coating radiator pigments. Trimethylindium and ozone were used as precursors for IO, while a tetrakis(dimethylamino)tin(IV) source was used for Sn doping to produce ITO. As-deposited IO films prepared at 140 °C resulted in a growth per cycle of 0.46 Å/cycle and film resistivity as low as 1.4×10−3 Ω cm. For the case of ITO thin films, an ALD process supercycle consisting of 1 Sn + 19 In cycles is shown to provide the optimum level of Sn doping corresponding to 10 wt. % widely reported in the literature.

Gas Sensing Properties of In₂O₃ Nano-Films Obtained by Low Temperature Pulsed Electron Deposition Technique on Alumina Substrates.

Nanostructured Indium(III) oxide (In2O3) films deposited by low temperature pulsed electron deposition (LPED) technique on customized alumina printed circuit boards have been manufactured and characterized as gas sensing devices. Their electrical properties have monitored directly during deposition to optimize their sensing performance. Experimental results with oxidizing (NO2) as well as reducing (CO) gases in both air and inert gas carriers are discussed and modeled.

Collective energy gap of preformed Cooper pairs in disordered superconductors

In most superconductors the transition to the superconducting state is driven by the binding of electrons into Cooper-pairs. The condensation of these pairs into a single, phase coherent, quantum state takes place concomitantly with their formation at the transition temperature, $T_c$. A different scenario occurs in some disordered, amorphous, superconductors: Instead of a pairing-driven transition, incoherent Cooper pairs first pre-form above $T_c$, causing the opening of a pseudogap, and then, at $T_c$, condense into the phase coherent superconducting state. Such a two-step scenario implies the existence of a new energy scale, $\Delta_{c}$, driving the collective superconducting transition of the preformed pairs. Here we unveil this energy scale by means of Andreev spectroscopy in superconducting thin films of amorphous indium oxide. We observe two Andreev conductance peaks at $\pm \Delta_{c}$ that develop only below $T_c$ and for highly disordered films on the verge of the transition to insulator. Our findings demonstrate that amorphous superconducting films provide prototypical disordered quantum systems to explore the collective superfluid transition of preformed Cooper-pairs pairs.

Si-doping effect on solution-processed In-O thin-film transistors

In this work, silicon-doped indium oxide thin-film transistors (TFTs) have been fabricated for the first time by a solution processing method. By varying the Si concentration in the In2O3–SiO2 binary oxide structure up to 15 at%, the thicknesses, densities, and crystallinity of the resulting In–Si–O (ISO) thin films were investigated by x-ray reflectivity (XRR) and x-ray diffraction techniques, while the produced TFTs were characterized by a conventional three-probe method. The results of XRR analysis revealed that the increase in the content of Si dopant increased the thickness of the produced film and reduced its density, and that all the Si-doped ISO thin films contained only a single amorphous phase even after annealing at temperatures as high as 800 °C. The manufactured ISO TFTs exhibited a reduction in the absolute value of threshold voltage VT close to 0 V and low current in the off-state, as compared to those of the non-doped indium oxide films, due to the reduced number of oxygen defects, which was consistent with the behavior of ISO TFTs fabricated by a sputtering method. The ISO TFT with a Si content of 3 at% annealed at 400 °C demonstrated the smallest subthreshold swing of 0.5 V/dec, VT of −5 V, mobility of 0.21 cm2 V−1s−1, and on/off current ratio of about 2 × 107.

Electrical Properties of Indium-Oxide Thin Films Produced by Plasma-Enhanced Reactive Thermal Evaporation

The structure and electrical properties of transparent indium-oxide thin films produced by plasma-enhanced reactive thermal evaporation at different substrate temperatures are studied. It is found that the films have a grained structure. An increase in the substrate temperature yields a considerable increase in the conductivity of the films and a decrease in the photoconductivity-relaxation time. An interpretation of the effect of the substrate temperature on the observed changes in the electrical and photoelectric properties of the indium-oxide films under study is proposed.

Low-temperature anomaly in disordered superconductors near B c2 as a vortex-glass property.

Strongly disordered superconductors in a magnetic field display many characteristic properties of type-II superconductivity—except at low temperatures, where an anomalous linear temperature dependence of the resistive critical field Bc2 is routinely observed. This behavior violates the conventional theory of superconductivity, and its origin has posed a long-standing puzzle. Here we report systematic measurements of the critical magnetic field and current on amorphous indium oxide films with various levels of disorder. Surprisingly, our measurements show that the Bc2 anomaly is accompanied by mean-field-like scaling of the critical current. Based on a comprehensive theoretical study we argue that these observations are a consequence of the vortex-glass ground state and its thermal fluctuations. Our theory further predicts that the linear-temperature anomaly occurs more generally in both films and disordered bulk superconductors, with a slope that depends on the normal-state sheet resistance, which we confirm experimentally.

Photodegradation Activity of Sputtered Indium Oxide and Suboxide Thin Films on Rhodamine-B Dye

The relationship between the oxygen composition of In2O3 thin films and their photodegradation capabilities has not been elucidated previously. In this investigation, the electronic and material ch...

Effect of Heat Treatment on the Electrical Properties of Thin Yttrium-Doped In2O3 Films

Thin indium oxide films and In–Y–O films containing 0.7 to 3.6 at % Y have been grown by ionbeam sputtering of an indium target and a composite (indium + weighed amounts of yttrium) target in a mixture of argon and oxygen. The thin indium oxide films have a cubic crystal structure (sp. gr. Ia $$\bar 3$$ ). The incorporation of yttrium atoms into indium oxide leads to the formation of an amorphous structure in the as-grown films and an increase in their room-temperature electrical resistance by several orders of magnitude. Lowtemperature electrical resistance data indicate a change in conduction mechanism. High-temperature heat treatment of the thin In–Y–O films leads to the crystallization of their amorphous structure and an increase in their electrical resistance.

Effect of growth temperature on the structural and optoelectronic properties of epitaxial indium oxide films

High quality monocrystalline indium oxide (In2O3) films have been epitaxially grown on SiO2 (0001) substrates by the metal-organic chemical vapor deposition (MOCVD) method. The influences of different growth temperatures on the structural, morphological and optoelectronic properties of the films were studied in detail. The film deposited at 650 °C exhibited the narrowest X-ray linewidth with an epitaxial relationship of In2O3 (1 1 1)∥SiO2 (0001). The highest Hall mobility of 27.84 cm2 V−1 s−1 with a minimum carrier concentration of 5.03 × 1019 cm−3 and a minimum resistivity of 4.24 × 10−3 Ω cm was obtained for the film prepared at 650 °C. The average transmittance for all the samples in the visible range exceeded 82% and the optical band gap of the films was calculated about 3.7 eV.

Quantum Criticality at the Superconductor-Insulator Transition Probed by the Nernst Effect.

The superconductor-insulator transition (SIT) is an excellent example of a quantum phase transition at zero temperature, dominated by quantum fluctuations. These are expected to be very prominent close to the quantum critical point. So far, most of the experimental studies of the SIT have concentrated on transport properties and tunneling experiments that provide indirect information on criticality close to the transition. Here we present an experiment uniquely designed to study the evolution of quantum fluctuations through the quantum critical point. We utilize the Nernst effect, which has been shown to be effective in probing superconducting fluctuation. We measure the Nernst coefficient in amorphous indium oxide films tuned through the SIT and find a large signal on both the superconducting and the insulating sides, which peaks close to the critical point. The transverse Peltier coefficient α_{xy}, which is the thermodynamic quantity extracted from these measurements, follows quantum critical scaling with critical exponents ν∼0.7 and z∼1. These exponents are consistent with a clean X-Y model in 2+1 dimensions.

Swift heavy ion induced modifications in the structural, optical and methane sensing properties of indium oxide thin films - A comparative study using Ag9+ and O7+ ion irradiation

Thin films of indium oxide grown on quartz substrates were subjected to 100 MeV Ag 9+ and O 7+ ions irradiation. The pristine and swift heavy ions irradiated films were characterized using X-ray Diffraction, Rutherford Backscattering Spectrometry, Scanning Electron Microscopy and UV-Vis Spectroscopy to examine the effect of irradiation with ions having large difference in the values of electronic energy loss (Se) on the structural, microstructural and optical properties of indium oxide thin films. XRD and SEM studies revealed deterioration in crystallinity along with decrease in both crystallite size and grain size upon irradiation with both Ag 9+ and O 7+ ions. However, the decrease in the crystallite size and grain size in comparison to the pristine film was more radical for irradiation with Ag 9+ ions. RBS spectra suggest that the electronic sputtering in the indium oxide films due to SHI irradiation is very less. AFM images illustrate the decrease in surface roughness from 29.8 nm for the pristine film to to 27.4 nm and 26.7 nm on irradiation with 100 MeV O 7+ and Ag 9+ ions at a fluence of 3.3×10 13 ions/cm 2 . Also, UV-Vis study revealed an increment in the value of optical band gap from 3.41 eV for the pristine film to 3.53 and 3.67 eV for indium oxide films irradiated with of 3.3×10 13 ions/cm 2 fluence of O 7+ and Ag 9+ ions respectively. The irradiation induced structural and optical modifications have been explained using the Thermal spike model. Along with the structural and optical properties, sensing properties of the pristine and irradiated films for 100 ppm methane gas at an operating temperature of 300 o C have also been examined and the results have been correlated with the induced structural modifications.

Transition to exponential relaxation in weakly disordered electron glasses

The out-of-equilibrium excess conductance of electron-glasses typically relaxes with a logarithmic time-dependence. Here it is shown that the log(t) relaxation of a weakly-disordered amorphous indium-oxide films crosses-over asymptotically to an exponential dependence. This allows assigning a well-defined relaxation-time t' for a given system-disorder (characterized by the Ioffe-Regel parameter). Near the metal-insulator transition, t' obeys the scaling relation with the same critical disorder where the zero-temperature conductivity of this system vanishes. The latter defines the position of the disorder-driven metal-to-insulator transition (MIT) which is a quantum-phase-transition. In this regard the electron-glass differs from classical-glasses such as the structural-glass and spin-glass. The ability to experimentally assign an unambiguous relaxation-time allows us to demonstrate the steep dependence of the electron-glass dynamics on carrier-concentration.

Low-Loss Near-Infrared Hyperbolic Metamaterials with Epitaxial ITO-In2O3 Multilayers

Artificial metamaterials with hyperbolic dispersions exhibit unusual optical properties not found in Nature. Such hyperbolic metamaterials (HMMs) permit the access to and control of electromagnetic waves with large wave vectors. An important criterion for multilayer-based HMMs is whether the thickness of each individual layer can be far below the operating wavelength while still maintaining the material and interfacial quality. Herein, we report heteroepitaxial growth of HMMs composed of multilayers of ultrathin indium tin oxide (ITO) and indium oxide (In2O3) films. The disparate metallic and dielectric properties of the individual building blocks, in conjunction with the good carrier mobility and film morphology enable a low-loss infrared HMM platform on which we demonstrate ultrafast optical switching and the enhancement of the radiative decay rate of PbS quantum dots in the telecommunication wavelength regime.

Ultraviolet light-induced terahertz modulation of an indium oxide film.

Active ultraviolet light-induced terahertz modulation of an indium oxide film is investigated. A large absorption modulation of ~66% is achieved upon illumination with a low intensity UV laser (11 mW/cm2). The interaction between indium oxide and a flexible metamaterial structure is investigated owing to the large UV-induced enhancement of photo carriers observed in an indium oxide film. We are able to realize absorption peak shifts of 37 GHz by changing the UV excitation light intensity. We also propose a multi-frequency switch by building a circular metallic split ring resonator whose gaps are filled with silicon, germanium, and indium oxide. In future, a photo-excited tunable multi-frequency metamaterial switch can be realized by irradiating the structure with multi-wavelength laser beam.

Highly conductive flexible ultra thin ITO nanoclusters prepared by 3-D confined magnetron sputtering at a low temperature

Flexible ultra-thin indium oxide films (UT-ITOs) of 30–50nm thick, with crystallized nanoclusters (NCs), exhibiting excellent resistivity as low as ~5.6×10−4Ωcm are deposited at ~80°C without heating using a new 3-D confined magnetron source (3DMS). Material characteristics are purposefully investigated in light of NC formation. Also, the measured NC sizes are reasonably comparable to the theoretically estimated values obtained using a two-body collision model that reveals the formation of NCs by add-atoms.

Enhanced Field Electron Emission from Photocurrent Treated Nanostructured Indium Oxide Films

Field electron emission currents from nanostructured films always have unsatisfied stability. This paper introduces a photocurrent treatment technique to enhance the filed emission properties, and gives a kind of nanostructured indium oxide film suitable for the technique. The products were prepared on patterned ITO glass substrate by using chemical vapor deposition method. With the increase of reaction time, the morphologies of the films changed from cocoonlike particles to hybrid thin films, and finally flowerlike nanostructures were formed. Photocurrent and field electron emission characteristics of the products have been studied. After photocurrent treatment, the flowerlike indium oxide films show stable field emission current (fluctuation is less than 5%), low field emission threshold (at 7.5 V/m, the current density is 1 mA/cm2) and high enhancement factor of electrical field of 778. The field emission test results validated that the photocurrent treated flowerlike indium oxide films may act as electron emitters and applied in display applications.

Фотопроводимость пленок оксида индия легированных галлием в ультрафиолетовой области

Фотопроводимость пленок оксида индия легированных галлием в ультрафиолетовой области

Электрические свойства тонких пленок оксида индия, полученных методом плазменно-термического испарения

AbstractThe structure and electrical properties of transparent indium-oxide thin films produced by plasma-enhanced reactive thermal evaporation at different substrate temperatures are studied. It is found that the films have a grained structure. An increase in the substrate temperature yields a considerable increase in the conductivity of the films and a decrease in the photoconductivity-relaxation time. An interpretation of the effect of the substrate temperature on the observed changes in the electrical and photoelectric properties of the indium-oxide films under study is proposed.

Instability of Insulators near Quantum Phase Transitions.

Thin films of amorphous indium oxide undergo a magnetic field driven superconducting to insulator quantum phase transition. In the insulating phase, the current-voltage characteristics show large current discontinuities due to overheating of electrons. We show that the onset voltage for the discontinuities vanishes as we approach the quantum critical point. As a result, the insulating phase becomes unstable with respect to any applied voltage making it, at least experimentally, immeasurable. We emphasize that unlike previous reports of the absence of linear response near quantum phase transitions, in our system, the departure from equilibrium is discontinuous. Because the conditions for these discontinuities are satisfied in most insulators at low temperatures, and due to the decay of all characteristic energy scales near quantum phase transitions, we believe that this instability is general and should occur in various systems while approaching their quantum critical point. Accounting for this instability is crucial for determining the critical behavior of systems near the transition.