Tin-doped Indium Oxide Thin Films Research Articles

Investigation of optoelectronic properties of tin-doped indium oxide thin films and contact resistivity with silver film: Role of oxygen concentration variation during sputter deposition

Investigation of optoelectronic properties of tin-doped indium oxide thin films and contact resistivity with silver film: Role of oxygen concentration variation during sputter deposition

Effect of oxygen flow on electrical and optical properties of ITO films synthesized by magnetron sputtering method

The tin-doped indium oxide thin films were synthesized by DC magnetron sputtering on the surface of polished silicon samples and glass slides in a mixed argon-oxygen atmosphere. The other deposition parameters: operating pressure, magnetron power and substrate rotation speed were kept constant. Thickness and density of thin films were measured by X-ray Reflectometry. The effects of oxygen flow rate and substrate temperature on the optical and electrical properties were investigated. The electrical properties (resistivity, Hall mobility and charge concentration) of the thin films were measured by the Van der Pauw method using the Hall effect. The minimum value of resistivity 0.52 × 10-3 Ohm·cm, and maximum charge mobility 28 cm2V-1s-1 was achieved at an oxygen proportional gas mixture of 2.6% (0.71 sccm). The transmission spectra of the films were measured in the wavelength range from 300 to 1100 nm. The transmittance of all films exceeds 75% in the visible and near-infrared spectral ranges. It was found that increasing the oxygen flow rate and heating of the substrate up to optimal value 150°C led to an increase in the crystallinity of the films and, consequently, to an increase in the Hall mobility and the transmittance.

Simple preparation of nanoporous ITO film with novel sparking method

We present a practical and simple method for the fabrication of nanostructured, highly transparent and conductive, porous tin-doped indium oxide (ITO) thin films via a novel sparking method. The pore structure consists of the densely packed secondary nanoparticles, which is the highlight of our sparking method, was observed through FE-SEM images. The crystallization and oxidation of the films occurred during the post-annealing process, where the XRD patterns confirmed the polycrystalline in nature and crystallizes in a cubic structure of In2O3. Our porous ITO films provide good conductivity with resistivity of 4.6 × 10−3 Ω.cm and large transmittance of 84% for films prepared at 160 s deposition time with an indium/tin atomic ratio of 90:10 and post-annealed at 500 °C for 3 h, which are potential materials for optoelectronic applications.

Controlled Lattice Thermal Conductivity of Transparent Conductive Oxide Thin Film via Localized Vibration of Doping Atoms.

Amorphization using impurity doping is a promising approach to improve the thermoelectric properties of tin-doped indium oxide (ITO) thin films. However, an abnormal phenomenon has been observed where an excessive concentration of doped atoms increases the lattice thermal conductivity (κl). To elucidate this paradox, we propose two hypotheses: (1) metal hydroxide formation due to the low bond enthalpy energy of O and metal atoms and (2) localized vibration due to excessive impurity doping. To verify these hypotheses, we doped ZnO and CeO2, which have low and high bond enthalpies with oxygen, respectively, into the ITO thin film. Regardless of the bond enthalpy energy, the κl values of the two thin films increased due to excessive doping. Fourier transform infrared spectroscopy was conducted to determine the metal hydroxide formation. There was no significant difference in wave absorbance originating from the OH stretching vibration. Therefore, the increase in κl due to the excessive doping was due to the formation of localized regions in the thin film. These results could be valuable for various applications using other transparent conductive oxides and guide the control of the properties of thin films.

Investigation of the effect of temperature on the structural, optical, electrical, and self-cleaning properties of ITO thin films

Transparent conductive tin-doped indium oxide (In2O3:Sn, ITO) thin films have been deposited onto glass substrate at different substrate temperatures by a simple and inexpensive method of air pressure chemical vapor deposition. The structural characteristics, and optical, electrical, and self-cleaning properties of the ITO thin films were investigated. It is clear that all films have a polycrystalline structure. In the sample synthesized at 550 °C, the preferred growth direction is in the direction of (222), but in the films synthesized at 450° and 500 °C, it is in the direction of (400). In the FESEM figures for all temperatures, the size of the nano-particles is less than 35 nm. In addition, all films have a relatively uniform surface. The analysis (EDX) was used to determine the chemical composition of these films. Transmission and reflection spectra of these films were examined in the 300–1000 nm spectral range and, for investigated films, the transmission coefficients in the visible regions exceed 80% and are weakly affected by deposition temperature. The optical band-gap values, Eg, ranged between 4.1 and 4.2 eV. In self-cleaning properties, the sample synthesized at 550 °C had the highest roughness and the highest contact angle and is a relatively good hydrophobic surface.

Origins of infrared transparency in highly conductive perovskite stannate BaSnO3

Near-infrared absorption in transparent conducting oxides (TCOs) is usually caused by electronic intraband transition at high doping levels. Improved infrared transparency is commonly explained by enhanced drift mobility in these TCOs. Here, an alternative cause behind the high infrared transparency of La-doped barium stannate (LBSO) transparent electrodes is presented. Following the Drude model formalism, we reconstructed spectrally resolved dielectric permittivity for a set of thin films with different free electron concentrations. A comparison of optical properties of LBSO with the tin-doped indium oxide thin films with identical carrier concentrations suggests that the redshift of the screened plasma wavelength for LBSO originates from its large high-frequency dielectric constant of 4.4, one of the highest reported for the s-orbital-based TCOs. Moreover, our measurements confirm an optical mobility significantly higher (>300 cm2/V s) than the drift mobility, effectively suppressing the free carrier absorption. These factors enable high infrared transparency of LBSO films and motivate further exploration of LBSO as broadband TCOs for solar cells and nanophotonics.

Optoelectric Property and Flexibility of Tin-Doped Indium Oxide (ITO) Thin Film.

Transparent conducting electrodes (TCEs) are key materials for electronic devices such as flat panel displays (e.g., a liquid crystal display and a light emitting diode display), photovoltaic cells, and transparent transistors. Tin-doped indium oxide (ITO) is known to be highly conductive/transparent, but rigid. In this study, very thin (<35 nm) ITO films with amorphous phases were prepared on flexible substrates and their optoelectric properties investigated. A 10 nm-thick ITO film was also fabricated. Because of their low thickness, their transmittances were above 80% at ˜550 nm wavelength. Their sheet resistances were below 0.7 kΩ/sq and decreased with increasing film thickness. An interesting observation was that their sheet resistances were nearly unchanged even at a bending radius of ˜2 mm. These optoelectric properties and flexibility demonstrate that the ITO films fabricated in this study are suitable transparent conducting oxides for the electrodes of flexible optoelectric devices.

Nanostructure and Physical Properties Control of Indium Tin Oxide Films Prepared at Room Temperature through Ion Beam Sputtering Deposition at Oblique Angles

In this paper, we report the fabrication of porous and crystalline tin-doped indium oxide (ITO) thin films at room temperature by ion beam sputtering deposition at oblique angles using either argon or xenon ions. Deep insights into these systems are provided by coupling nanostructural (scanning and transmission electron microscopies, X-ray diffraction) and optical (spectroscopic ellipsometry, spectral reflectometry) characterizations. This original approach allows extracting important features of the films (porosity, refractive indexes, in-grain carrier densities, and mobilities) not easy to reach locally by other techniques. We propose a model decomposing the complex film’s nanostructure into two layers presenting different electro-optical properties, which are attributed to the shadowing effect, but also to the presence of growth defects and impurities due to the atomic peening. In particular, we demonstrate that ITO films deposited with Xe present a better crystallinity and larger porosity, providing s...

Investigation of physical properties and surface free energy of produced ITO thin films by TVA technique

In this study, tin-doped indium oxide (ITO) thin films with composition of 10% SnO2 and 90% In2O3 have been produced onto glass, polyethylene terephthalate (PET) and Silicon (Si) substrates by using thermionic vacuum arc technique. The properties of the ITO thin films were determined various tolls such as an X-ray diffraction (XRD), ultraviolet–visible (UV–Vis) spectrophotometer, optical reflectometer, field emission electron microscopy (FESEM), atomic force microscopy, four-point probe and contact angle (CA) measurements devices. According to the XRD patterns, deposited thin films onto glass, PET and Si substrate are in amorphous structure. The thicknesses of the deposited layers are very close to each other’s and films. The transmittance values are approximately 30% at 632 nm. Refractive index of the deposited layers are close to 1.75, but optical band gaps are found 3.88 and 3.81 eV for the thin film deposited onto glass and PET substrate, respectively. These values are bigger than the value of the band gap value of the ITO material. In surface analysis, it was found that crystallite dimensions are in nano-scales. According to surface analysis, nano-crystalline ITO thin films were deposited. The contact angle of the coated ITO layer were measured in the range of 98°–110°. The electrical resistivity of films was calculated about 0.65 × 10−5 Ω cm for ITO/glass, 1.05 × 10−5 Ω cm for ITO/PET and 5.82 × 10−5 Ω cm for ITO/Si.

Enhancing electrical conductivity of room temperature deposited Sn-doped In2O3 thin films by hematite seed layers

Hematite Fe2O3 seed layers are shown to constitute a pathway to prepare highly conductive transparent tin-doped indium oxide thin films by room temperature magnetron sputtering. Conductivities of up to σ = 3300 S/cm are observed. The improved conductivity is not restricted to the interface but related to an enhanced crystallization of the films, which proceeds in the rhombohedral phase.

Atomic oxygen irradiation resistance of transparent conductive oxide thin films

One set of tungsten-doped indium oxide thin films (In2O3:W, IWO) and another set of tin-doped indium oxide thin films (In2O3:Sn, ITO) were prepared on glass substrates by radio frequency (RF) reactive magnetron sputtering method. The as-deposited IWO and ITO films have resistivity values at a level of 10−4Ω•cm. Average transmittance values of these films are above 85% in visible-light region as well as in near-infrared region. All these films were irradiated by atomic oxygen (AO) with different amount of flux in a ground-based simulation system close to the environment of low Earth orbit. Changes in characteristics including surface morphology, mechanical properties, optical and electrical properties were compared between IWO and ITO films after AO irradiation. The effects of AO irradiation on transparent conductive oxide thin films were analyzed. As a result, AO has influences on ITO and IWO thin films through the way of oxidation and erosion. Both ITO and IWO films possess suitable anti-AO properties. IWO films are more appropriate as AO protective coatings due to their compact microstructure, the coexistence of W4+ and W6+ ions in their chemical systems, and incremental WO3 protective layer under AO oxidation.

Optical properties of undoped and tin-doped nanostructured In2O3thin films deposited by spray pyrolysis

Tin-doped indium oxide (In 2 O 3 :Sn) thin films in different concentrations (Sn = 0, 3, 5, 8 at.%) were deposited by reactive chemical pulverisation spray pyrolysis on heated glass substrates at 500 °C. The effect of the tin dopant on the nonlinear optical properties was investigated using X-ray diffraction, transmission, electrical resistivity and third harmonic generation (THG). All films were polycrystalline, and crystallised in a cubic structure with a preferential orientation along the (400) direction. The Sn (5 at.%) doped In 2 O 3 thin films exhibited a lower resistivity of 3 × 10 -4 Ω cm, and higher transmission in the visible region of about 94%. Optical parameters, such as the extinction coefficient ( k ), refractive index ( n ) and energy band gap ( E g ), were also studied to show the composition-dependence of tin-doped indium oxide films. The nonlinear properties of the In 2 O 3 :Sn thin films have been found to be influenced by doping concentration, and the best value of χ (3) = 3 × 10 -11 (esu) was found for the 5 at.% doped sample.

Studies on the structural, optical, and electrical properties of jet-nebulized spray pyrolysis ITO thin films

In this study, tin-doped indium oxide (ITO) thin films were fabricated via jet-nebulized spray pyrolysis method. The structural, micro structural, and optical properties of the ITO thin films were investigated via X-ray diffraction (XRD), ultraviolet–visible spectroscopy, and scanning electron microscopy (SEM). The XRD patterns of the thin films indicated a preferred orientation along the (222) plane, which ensures the formation of a pure phase with a high degree of crystallinity. The PL analysis showed that the film has a high transmittance of 80 %. The SEM observations showed the formation of dense films with grain sizes in the range of 25–50 nm. The X-ray photoelectron spectroscopy results displayed the single valance state and chemical bonding state of In and Sn in indium tin oxide. The electrical resistivity of the ITO substantially changed with the incorporation of Sn into the In2O3 structure. When 10 wt% Sn was added as a dopant, the minimum resistivity was 0.10 Ω-m.

Highly transparent and conductive indium tin oxide thin films for solar cells grown by reactive thermal evaporation at low temperature

Transparent conductive tin-doped indium oxide (In2O3:Sn, ITO) thin films with various Sn-doping concentrations have been prepared using the low cost reactive thermal evaporation (RTE) technique at a low growth temperature of ~160 °C. The structural characteristics, optical and electrical properties of the ITO thin films were investigated. These polycrystalline ITO films exhibited preferential orientation along (222) plane and possessed low resistivities ranging from 3.51 to 5.71 × 10−4 Ω cm. The decreased mobility was attributed to the scattering by ionized and neutral impurities at high doping concentrations. The optimized ITO thin film deposited with 6.0 wt% Sn-doping concentration exhibited a high average transparency of 87 % in the wavelength range of 380–900 nm and a low resistivity of 3.74 × 10−4 Ω cm with a high Hall mobility of 47 cm2 V−1s−1. A hydrogenated amorphous silicon and silicon–germanium (a-Si:H/a-SiGe:H) double-junction solar cell fabricated with the RTE-grown ITO electrodes presented a conversion efficiency of 10.51 %.

Morphology and structure evolution of tin-doped indium oxide thin films deposited by radio-frequency magnetron sputtering: The role of the sputtering atmosphere

The microstructure and morphology evolution of tin-doped indium oxide (ITO) thin films deposited by radio-frequency magnetron sputtering in different sputtering atmospheres were investigated by X-ray diffraction, X-ray reflectivity, and atomic force microscopy. The surface roughness w increases with increasing film thickness df, and exhibits a power law behavior w ∼ dfβ. The roughness decreases with increasing O2 flow, while it increases with increasing H2 flow. The growth exponent β is found to be 0.35, 0.75, and 0.98 for depositions in Ar/10%O2, pure Ar, and Ar/10%H2 atmospheres, respectively. The correlation length ξ increases with film thickness also with a power law according to ξ ∼ dfz with exponents z = 0.36, 0.44, and 0.57 for these three different gas atmospheres, respectively. A combination of local and non-local growth modes in 2 + 1 dimensions is discussed for the ITO growth in this work.

Design of process diagnostics for excimer laser irradiation of oxide thin films

The authors have developed an in situ excimer laser irradiation system that can monitor the temperature field of oxide thin films through thermal radiation produced upon a pulsed ultraviolet laser irradiation. Thermal emission signals from a Si single crystal obtained using with this system agreed well with a numerical simulation result, validating the time constant of the measurement system. The time-dependent transient temperature profile of tin-doped indium oxide thin films, which was converted from thermal emission signals, clearly showed a recalescence behavior in its cooling curve. The transmittance data of the laser-irradiated indium oxide thin films suggested that the transmittance monitoring at near-infrared and ultraviolet–visible regions could be useful in monitoring the dopant levels and laser processing conditions, respectively.

The effect of solvents and the thickness on structural, optical and electrical properties of ITO thin films prepared by a sol–gel spin-coating process

In this study, tin-doped indium oxide (ITO) thin films were produced by the sol–gel spin-coating technique with an inexpensive salt of indium (In(NO3)3·H2O) and SnCl4 as indium and tin precursors (the molar ratio of In:Sn was 9:1), respectively. Then the prepared thin films were annealed in the temperature of 550 °C under argon atmosphere (the pressure of 10 torr). Polyvinylalcohol (PVA) was used as stabilizers in the synthesis of ITO sol. The prepared ITO thin films were characterized by EDX, XRD, FT-IR, UV–Vis spectroscopy and SEM images. The XRD patterns of the thin films indicated the main peak of the (2 2 2) plane corresponded to indium oxide with high degree of crystallinity. The FT-IR spectroscopy confirmed that indium tin oxide has been prepared by appearance of a peak at 470 cm−1 that can be assigned to the vibrations of In–O bonds. The optical direct band gap of ITO thin films was calculated about 3.98–4.17 eV by optical transmittance measurements. The grain size of ITO nanoparticles was obtained at about 25–50 nm by SEM images. The electrical characterization was done by the four-point probe method to determine the sheet resistance and resistivity. The effects of coating number on ITO thin films properties were investigated. The low resistivity (sheet resistance of 2.5 kΩ/cm2) and highly transparent films were obtained that can be applied as covers on heater windows. Appearance of a peak at 470 cm−1 can be assigned to the vibrations of In–O bonds and are characteristic of cubic In2O3.

A Reclamation System via a Pins-Module Tool for Touch Sensing Material Surfaces

This study demonstrates a designed pins-module tool and a precise reclamation system using a micro electroremoval process for sensing material of tin-doped indium oxide thin-films dissolved from a surface of polyethylene terephthalate of touch-panel. In the current experiment, a higher dissolution rate of the defective tin-doped indium oxide corresponds to high rotational speed of the cylinders tool with large flow rate of the electrolyte. A small diameter of the anode or a small diameter of the cathode combined with enough electric power, results in fast dissolution. The removal rate of tin-doped indium oxide thin-film is improved by decreasing the cylinders number. Importantly, the performance of a designed pins-module tool was found to be more effective in the micro electroremoval process. It requires only a short period of time to dissolve the nanostructured of tin-doped indium oxide easily and cleanly.

Effect of Span-80 in n-Hexadecane on Surface Tensions at High Temperatures

Drop formation and release, spreading and wetting of substrate, etc., are interfacial phenomena that are critical to the performance of many high-speed processes in digital printing and fabrication. In these instances, dynamic surface tension (surface tension as a function of time) in the presence of a surfactant is more important in evaluating the performance of the process than its equilibrium surface tension. It is known that temperature change can cause a change in the adsorption kinetics of ionic and nonionic surfactants at interfaces resulting in a change in equilibrium surface tension measured with temperatures [1-4]. We have recently reported [5] high-temperature measurements (up to 200 &#xB0;C) of surface tensions using optical imaging of the liquid/gas interface inside a tapered micropipette created within a comparable sized micro-capillary that was heated by coating an electrically conductive, transparent, tin-doped indium oxide (ITO) thin film. This novel method is further used in the current study for: (i) determining high-temperature equilibrium surface tensions of a non-ionic surfactant, Span-80 in n-Hexadecane (up to 160 &#xB0;C) and comparing the results with those of the pure liquids6 and; (ii) investigating the effects of this surfactant on the dependence of surface tensions on temperature and time when the equilibrium is perturbed by a rapid temperature-change. The interesting aspect of the surfactant selection is that it is not normally surface active at the air/ n-hexadecane interface at room temperatures but is extremely surface active at high temperatures. Results show that, as expected, surface tension decreases as temperature increases and vice-versa. The values determined by optical measurements closely match the values obtained using theory of corresponding states. Also, the time to attain equilibrium is very short (a fraction of a second) and there is hysteresis in dynamic surface tensions between the temperature increase and decrease cycles with the decrease cycle lagging behind the increase cycle. Surfactant concentration is important in affecting dynamic surface tension but does not seem to play a significant role in the reduction of equilibrium surface tensions.

Video microscopic high-temperature measurement of surface tension

In this paper, a micropipette-in-microcapillary method and its experimental setup are described for the study of temperature effects on surface tension. Temperature control within the confined space of a capillary was achieved by coating the outer surface of the housing microcapillary with an electrically conductive, transparent, tin-doped indium oxide (ITO) thin film as a heating jacket. The precision of this technique was discussed according to the comparisons of our results with published reference data for water, n-hexadecane, and n-decane at room temperature. The technique was further used to measure the temperature-dependent surface tension of n-decane between 25°C and 110°C and n-hexadecane from 25°C to 200°C. The results were in excellent agreement with available published values, and also indicated linear decrease rates of surface tension with decreasing temperatures.