ITO Thin Films Research Articles

Enhanced visible light photoelectrochemical performance of β-Bi2O3-TiO2/ITO thin films prepared by aqueous sol-gel

Semiconductor heterojunction of β-Bi2O3-TiO2/ITO thin films was prepared by aqueous sol-gel and their photoelectrochemical and photoelectrocatalytic properties were evaluated on the oxidation of salicylic acid. The β-Bi2O3 sol precursor properties were characterized by DLS, SEM, and X-ray diffraction. The composition and morphology of the films were characterized by SEM-EDS. The photoelectrochemical characterization was performed by linear sweep voltammetry with chopped light irradiation and photocurrent measurements. The photoelectrocatalytic activity of the films under UV-Vis and visible light irradiation was conducted on the oxidation of salicylic acid. Results show that the films are composed of a TiO2 layer with Bi2O3 particles dispersed throughout the surface. X-ray diffraction results confirm that the Bi2O3 obtained from the sol precursor prepared corresponds to β-tetragonal phase. The linear sweep voltammetry shows that the β-Bi2O3-TiO2/ITO films have a higher photocurrent in the anodic region than TiO2/ITO films used as reference. The photoelectrocatalytic activity of the β-Bi2O3-TiO2/ITO films on the oxidation of salicylic acid under visible light irradiation was higher than TiO2/ITO films. The results show that the β-Bi2O3-TiO2/ITO films are active under visible light and can be used in photoelectrochemical cells.

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.

Solution assisted roll-coating of transparent conducting oxide thin films for organic photovoltaic applications

Transparent conduction oxide (TCO) thin films are one of the key material in optoelectronic applications. These materials are usually produced by vacuum-based methods such as magnetron sputtering, both for laboratory work and for commercial purposes. Alternative methods for producing large-scale TCO films are needed. In this work, a non-vacuum coating technique for preparation of TCO thin films on large area glass substrates was presented. Tin doped indium oxide (ITO) thin films were successively coated on glass substrates by non-vacuum based roll coating method. A low electrical resistivity of ~1.3 × 10−3 Ωcm and high optical transmittance of 84% in the visible region were obtained for ITO thin film samples. Furthermore, an ITO/PEDOT PSS/P3HT:PCBM/LiF/Al structured organic photovoltaic cell was also prepared on non-vacuum roll coated ITO thin films. The device with the roll coated ITO thin film exhibits a power conversion efficiency of 1.83%, average short-circuit current density (Jsc) of 7.4 mA/cm2, open-circuit voltage (Voc) of 0.590 V, and fill factor (FF) of 0.42.

Further optimization of ITO films at the melting point of Sn and configuration of Ohmic contact at the c-Si/ITO interface

Progressive improvement in the TCO characteristics of ITO (In2O3:Sn) thin films grown at substrate temperature (TS ∼ 232 °C) near the melting point of Sn has been pursued via optimization of gas pressure in the RF magnetron sputtering system. The optical transmission characteristics virtually remain consistently impressive on varying the gas pressure; however, crystallinity improves with significant dominance along 〈222〉 crystallographic orientation at an optimum gas pressure of 10 mTorr. Simultaneously, enhanced doping of the In2O3 network by Sn4+ active dopants along with optimum reducing condition attained at 10 mTorr pressure in the magnetron plasma provide maxima of both concentration and mobility of the charge carriers in the ITO films prepared at each substrate temperature in the range 200–350 °C and lead to a very high TCO figure of merit characteristics. At lower gas pressure below 10 mTorr, although dopant incorporation increases, formation of enhanced number of electrically inactive dopants (Sn2+) (reduced Sn4+/Sn2+ ratio) deteriorates the electrical characteristics of the ITO films. On lowering of gas pressure beyond the optimum reducing condition in the plasma, changes in the nature of decay of the concentration and mobility of the charge carriers depend sensitively on the substrate temperature. The carrier concentration reduces rapidly at higher TS while carrier mobility diminishes significantly at lower TS. Accordingly, dopant concentration and the oxidation state of the In2O3:Sn matrix together control the carrier characteristics in a complex manner which is again sensitively influenced by the substrate temperature and the working gas pressure of the magnetron plasma. Significantly superior ohmic contact of the optimum ITO film with c-Si wafer evolves due to narrowing of the junction barrier height (φB) arising by virtue of increased carrier concentration in ITO, thanks to effective doping by Sn4+. Improved c-Si/ITO junction characteristics admit supplementary application feasibility of ITO films in devices fabrication, particularly as transparent electrodes in c-Si p-n junction solar cells.

Potentiostatically pretreated electrochromic tungsten oxide films with enhanced durability: Electrochemical processes at interfaces of indium–tin oxide

Recent work has shown that electrochromic WO3 films, backed by In2O3:Sn (ITO) and immersed in a lithium-ion-conducting electrolyte, can attain unprecedented electrochemical cycling durability after potentiostatic pretreatment at high voltage. Here we demonstrate that this intriguing feature is associated with changes in the properties of the ITO film. Specifically, we studied thin films of ITO and WO3/ITO immersed in an electrolyte of LiClO4 in propylene carbonate at potentials up to 6.0 V vs. Li/Li+ by cyclic voltammetry and impedance spectroscopy and present evidence that electrochemical reactions occur under these conditions. X-ray photoemission spectroscopy indicated that the ITO film was partly dissolved at high voltages and that the dissolution reaction promoted diffusion of In and Sn into the WO3 film.

Ultra-thin Hafnium doped ZnO films with enhanced optical transparency and electrical conductivity

In this research, highly transparent and conducting hafnium doped zinc oxide (HZO) thin films were prepared by the simple sol-gel dip coating technique. Controlled doping process and synthesis method were used to improve the optical and electrical properties of HZO thin films. The structures, optical and electrical properties of the samples were characterized by XRD, XPS, FESEM, TEM, EDS, UV-Visible, and PL spectroscopy. Hall-effect measurement was performed to study the electrical properties of the HZO thin films. For the first time, HZO thin film with very low resistivity (4.2 × 10−3 Ω.cm) was prepared. At room temperature, strong green emission peak was observed for HZO thin films. Obtained results in this study are better than reported results before. This improvement may be related to the synthesis method of nanoparticles. HZO thin films may be an affordable candidate for optoelectronic device applications and a new replacement for ITO thin film.

Electrochromic device with magnetron sputtered tungsten oxide (WO3) and nafion membrane: performance with varying tungsten oxide thickness- a report

Electrochromics is the emerging technology for energy conservation and indoor climatic control through smart windows. In this study we are reporting four layer electrochromic device: ITO (400 nm)/commercially procured Nafion (183 μm)/WO3 (44 nm to 200 nm)/ITO (400 nm). The active area (A) of the electrochromic devices are 3 cm2. The tungsten oxide (WO3) and ITO thin films have been deposited at room temperature (300 K) by reactive DC Magnetron sputtering. The sheet resistance of ITO is 20 Ω/◻. The ‘as deposited’ WO3 films are amorphous and have high optical transmission (75%–85%) in the visible spectrum. The optical band gap decreases with increasing thickness of WO3 thin films. The coloration efficiency (CE) of the electrochromic device increases with increasing thickness of the WO3 layer. The CE for the device with WO3 thickness 200 nm is 184 cm2 C−1: the highest reported so far for a hybrid electrochromic device. The increase in the CE with thickness has been explained (for the first time) by replacing the surface charge density (Q/A) with the volume charge density (Q/A*t) in the coloration efficiency formula derived from the Beer Lambert’s law.

Effect of the Annealing Gas and RF Power Sputtering in the Electrical, Structural and Optical Properties of ITO Thin Films

Effect of the Annealing Gas and RF Power Sputtering in the Electrical, Structural and Optical Properties of ITO Thin Films

Influence of the DC Power on the Electrical and Optical Properties of ITO Thin Films Deposited on Nb2O5/SiO2 Buffer Layer

Influence of the DC Power on the Electrical and Optical Properties of ITO Thin Films Deposited on Nb2O5/SiO2 Buffer Layer

Microstructure and thermoelectric properties of In2O3/ITO thin film thermocouples with Al2O3 protecting layer

In2O3/ITO thin film thermocouples (TFTCs) with alumina protecting layer were fabricated on alumina substrates. The effects of protecting layer on their performance at higher temperature and long term service were investigated accordingly. In2O3 and ITO thin films were prepared by radio frequency magnetron sputtering methods, while the alumina protecting layer was prepared by traditional spin-coating methods. Microstructural and thermoelectric properties of the In2O3/ITO TFTCs with and without alumina (Al2O3) protecting layer were investigated as a function of sintering time from 2 to 10 h at 1250 °C. The results show that, the existence of alumina protecting layer can effectively increase the performance capabilities of thermocouples at high temperatures by inhibiting the volatilization of the thin film. In2O3/ITO TFTCs with protecting layer can work normally over 10 h at 1250 °C while Seebeck coefficient is 131.7 µV/°C. The drift rate can reach 3.05 °C/h, which is much better than those without protecting layer.

Infrared Transparency and Conductivity of Amorphous Ternary Ceramic Thin Films

In this paper, using polycrystalline Ti3SiC2 powder as target, for the first time, amorphous ternary ceramic (a-TSC) thin films are successfully fabricated on quartz and glass substrates at room temperature by direct-current (DC) sputtering. The microstructural and optoelectronic properties of the a-TSC thin films are investigated by means of XRD, Raman, EDS, four-point probe system and Vis-NIR spectrometer, respectively. It is found that despite of amorphous structure and having not so good conductivity compared with Ti3SiC2, the a-TSC thin films still have enough conductivity. Furthermore, compared with ITO, FTO and AZO thin films, the transmittance of a-TSC thin films is much higher in infrared region regardless of the film thickness. It is suggested for a-TSC thin films that the film thickness should be controlled less than 150nm in order to obtain a higher transparency with an appropriate conductivity. It is believed that a-TSC thin film will find its way to be applied in optoelectronic devices in the near future.

Influence of annealed ITO on PLD CZTS thin film solar cell

In this work, the influence of annealed ITO thin film as a transparent electrode layer in pulse laser deposition (PLD) Cu2ZnSnS4 (CZTS) thin-film solar cell was investigated. The proposed annealed ITO thin film exhibits a high degree of crystallinity and large and evenly distributed grains. Thus, low resistivity and wide and high transmitted band in the UV/VIS light range with ideal optical band gap of 3.8 eV can be obtained. Devices built with these annealed ITO thin films on our PLD CZTS solar cell exhibit a significant improvement in power conversion efficiency from 0.2% to 1.92%.

Structural and electric response of ITO/In2O3 transparent thin film thermocouples derived from RF sputtering at room temperature

Transparent thin film thermocouples have unique characteristics that it can be applied when permit minimal optical interference at in-situ temperature measurement. ITO/In2O3 thin film thermocouples were prepared on fused quartz glasses at room temperature by RF magnetron sputtering. For contrast, ITO thin films post-annealed at different temperatures were investigated accordingly. All films showed good conductivities, smooth surface morphology and high transmission, indicating negligible affection of the post-annealing temperature. The as-deposited ITO film has a Seebeck coefficient of 84.4 µV oC−1. The thermoelectric voltage of 13.6 mV and significantly lower drift rate of 2.39 °C h−1 were obtained at 190 °C for ITO/In2O3 thin film thermocouples without any heat treatment. This makes the ITO/In2O3 transparent thin film thermocouples great potential as a promising temperature sensor.

Magnetic, optical and electrical properties of ITO thin films implanted by cobalt ions

The Co doped ITO samples are prepared by Co ions implanted ITO thin films. The implantation dosage of Co ions is 5 × 1015, 1 × 1016, 2 × 1016 cm−2, respectively. Then the samples are annealed by rapid thermal annealing in vacuum. The structure of the samples is characterized by glancing angle X-ray diffraction and high resolution transmission electron microscopy. The observed dislocation causes the lattice distortion and the interplanar distance becomes larger. The carrier density gradually decreases as the Co ions dosage increases. The optical and electrical properties of the samples are affected by the carrier density. The gradually reduced band gap can be explained by Burnstein-Moss effect. Though the electrical and optical properties are deteriorated after Co implanted ITO thin films, the strength of ferromagnetism enhances as the dosage of Co ions increase.

Retrieval of Optical and Dielectric Constants of PBDTTTPD Polymer Film by Unconstrained Optimization Method

Till now, optical and dielectric constants of polymer based on poly(benzo[1,2-b:4,5-b’]- dithiophene–thieno [3,4-c]pyrrole-4,6-dione) (PBDTTPD) incorporated into thiophene (PBDTTTPD) have not been systematically investigated. In this work, PBDTTTPD thin film was prepared on ITO glass substrate. Transmittance spectra of ITO and PBDTTTPD films were measured. Based on unconstrained optimization method, the glass was firstly as the substrate, the thickness and the refractive index of the ITO were retrieved. Then the refractive index data of the ITO thin film were added to the PUMA program and the ITO was taken as the new substrate, the thickness, optical and dielectric constants of the PBDTTTPD film were further simulated only via the transmittance spectra. These optical and dielectric parameters are promising useful in design optical devices related to PBDTTTPD polymer.

One‐step Microwave‐assisted Synthesis of Indium Tin Oxide Nanoparticles for NIR‐Selective Dynamic Window Applications

AbstractIndium tin oxide (ITO) nanoparticles have been successfully synthesized by a one‐step microwave‐assisted environmentally benign method. By changing the molar ratio of In and Sn, the obtained ITO nanoparticles show the variation in particle size and morphology. When printed on conductive glass, ITO nanoparticles with different Sn content exhibit tunable adsorption properties in a near‐infrared (NIR) range. By regulating the surface electron density of the nanoparticles, their localized surface plasmon resonance (LSPR) can be dynamically and reversibly modulated. ITO nanoparticle was screen printed on conductive glass, followed by heat treatment, and was equipped with a counter electrode to obtain a NIR selective dynamic window with enhanced NIR optical contrast. The devices exhibited a 56% reversible modulation of the light transmission in a wide range from 750 to 2600 nm. The maximum variation of 74% was observed at 2000 nm. The charging and discharging mechanisms for ITO thin films were also investigated.

Thin film enabling sub-250 nm nano-ripples on glass by low fluence IR picosecond laser irradiation

Well-aligned parallel nanoripples, with spacing down to 250 nm, were engraved on a glass surface at a fluence 8 times less than the ablation threshold of glass using IR (λ = 1032 nm) picosecond laser system with a pulse duration of 10 ps. The glass surface was first coated with 175 nm ITO thin film prior to laser scanning. The nano-ripples were formed on the underlying glass surface during the selective removal of ITO thin film using substantially less fluence than that required without ITO on the glass surface. The laser scan speed and repetition rate determine the spatial overlapping of pulses (shots per area, SPA); this greatly influences the symmetry, spacing, and depth of the ripples achieved. The fluence ranging from 1.13 to 1.56 J cm−2 at scanning speed of 0.5 ms−1, 25 SPA, 96% overlapping at laser repetition of 400 kHz was found to be the optimal laser parameters for generating nano-ripples with 0.25λ periodicity on large area glass surface. The process offers the opportunity for gratings to be integrated in structures consisting of transparent conductive materials.

Approach for the optimization of characteristic properties of very high conductive ITO thin films using advanced magnetron plasma process

Highly transparent conductive ITO coatings with transparency ≥80% and resistivity ∼2.8 × 10−4 Ωcm are prepared directly by substrate heating using an advanced 3D confined high-density magnetron source (3DMS). The deposited ITO films exhibit excellent carrier concentration, mobility, and crystallinity at a moderate substrate temperature and without post-annealing. Data reveals that the combination of very high-density plasma at a low electron temperature and moderate substrate heating is favorable for developing ITO materials for transparent electrode applications. The electrical, optical, structural, and morphological properties of the deposited films are investigated in details in light of the plasma chemistry and substrate heating.

Surface morphological, structural, electrical and optical properties of GaN-based light-emitting diodes using submicron-scaled Ag islands and ITO thin films

An ITO-Ag islands complex as a new transparent conducting electrode (TCE) structure (on the 5 nm-thick p-InGaN/90 nm-thick p-GaN) for achieving high-performance and more reliable GaN-based LEDs were fabricated. A normal LED with a conventional ITO TCE was also compared. The surface morphological, structural, electrical and optical properties of fabricated GaN-based light-emitting diodes using a complex electrode of submicron-scaled Ag islands and ITO thin films are explored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) and output power-current (L-I) techniques. Surface morphology investigations revealed Ag islands formed uniformly on the p-InGaN/p-GaN surface during rapid thermal annealing at 400 °C for 1 min in N2 ambient. The ohmic properties and overall device-performance of the suggested contact and device structures were superior to those in the conventional ITO contact and normal ITO LED structures. Based on the results of XRD and XPS measurements, the formation of the intermetallic gallide phases (AgGa) is responsible for better performance characteristics of the ITO-Ag islands device. The significant improvements are described in terms of the conducting bridge influence, highly effective micro-mirror effect, and wider photon window via the roughened structure.

A Neural-Network Method of Predicting Defect Formation on the Surface of Thin ITO Films under Mechanical Load

A method for determining the number of defects arising under compressive and tensile stress in bended thin transparent conducting coatings on polymer substrates is proposed. This algorithm is based on the use of mathematical methods of artificial neural networks. The network is trained for calculating the average defect density per unit length at the input parameters corresponding to film and substrate sizes, surface resistance of the conducting coating, and bending radius. The application of this method allows one to determine the average defect density with high accuracy.