Indium Zinc Tin Oxide Films Research Articles

Encapsulation of flexible transparent electrodes based on indium zinc tin oxide with highly transparent and mechanically robust polymer dielectrics

This study was aimed at comprehensively investigating the utility of polymethyl methacrylate (PMMA) and CYTOP as encapsulation layers for flexible transparent electrodes composed of indium zinc tin oxide (IZTO). Optical modeling and experimental techniques were combined to assess the viability of PMMA and CYTOP as encapsulation materials. Optical modeling suggested that PMMA and CYTOP are well-suited for IZTO encapsulation. Subsequent experiment confirmed that the transmittance values of IZTO-films remained unaffected when encapsulated with PMMA and CYTOP. To examine the influence of encapsulation on mechanical resilience, all film, including untreated IZTO and IZTO treated with PMMA/CYTOP, were subjected to 20,000 bending cycles. The mechanical stability and optical properties of the IZTO film were considerably enhanced when encapsulated with these insulating materials. The improvement in transmittance was attributable to the lower refractive index of PMMA and CYTOP. Furthermore, scanning electron microscopy images demonstrated that the remarkable flexibility of PMMA and CYTOP effectively prevented the formation of cracks on the IZTO film, underscoring their pivotal role in enhancing the mechanical robustness of IZTO. In summary, this research highlights the potential of PMMA and CYTOP as efficient encapsulation materials for IZTO-based flexible transparent electrodes, offering dual benefits in terms of optical performance and mechanical durability.

Inkjet printing high mobility indium-zinc-tin oxide thin film transistor

Metal oxide thin film transistor has been widely used in flat panel display industry because of its low leakage current, high mobility and large area uniformity. Besides, with the development of printed display technology, inkjet printing process can fabricate the customizable patterns on diverse substrates with no need of vacuum or lithography to be used, thus significantly reducing cost and receiving more and more attention. In this paper, we use inkjet printing technology to prepare a bottom gate bottom contact thin film transistor (TFT) by using indium-zinc-tin-oxide (IZTO) semiconductor. The surface morphology of the printed IZTO film is modified by adjusting the solvent composition and solute concentration of the printing precursor ink. The experimental result show that the use of binary solvents can effectively overcome the coffee ring shape caused by the accumulation of solute edge in the volatilization process of a single solvent, ultimately presenting a uniform and flat contour surface. Further increase in solute concentration is in favor of formation of convex surface topology. The reason for the formation of the flat surface of the oxide film is the balance between the inward Marangoni reflux of the solute and the outward capillary flow during volatilization. In addition, IZTO thin film transistor printed with binary solvents exhibits excellent electrical properties. The ratio of width/length = 50/30 exhibits a high on-off ratio of 1.21×10<sup>9</sup>, a high saturation field-effect mobility is 16.6 cm<sup>2</sup>/(V·s), a low threshold voltage is 0.84 V, and subthreshold swing is 0.24 V/dec. The uniform and flat active layer thin film pattern can form good contact with the source leakage electrode, and the contact resistances of TFT devices with different width-to-length ratios are less than 1000 Ω, which can reach the basic conditions of high mobility thin film transistors prepared by inkjet printing. Therefore, using solvent mixture provides a universal and simple way to print oxide films with required surface topology, and present a visible path for inkjet printing of high-mobility thin film transistors.

Indium Zinc Tin Oxide Bottom Electrode‐Based Flexible Indoor Organic Photovoltaics with Remarkably High Mechanical Stability

The demand for flexible indoor organic photovoltaic cells (OPVs) is growing dramatically due to their simple and practical use as a powering aid for various electronic gadgets connected to the Internet of Things. Due to the brittleness of inorganic material‐based transparent bottom electrodes and their incompatibility with flexible organic substrates, it is extremely difficult to limit the influence of mechanical stress on the stability of flexible OPV. In this regard, choosing a mechanically stable and highly conductive transparent conducting oxide (TCO) is crucial. Therefore, flexible OPVs are fabricated onto a flexible (polyimide) substrate coated with mechanically stable TCO indium zinc tin oxide (IZTO). Sheet resistance measurements and observations of scanning electron microscope images of IZTO film after 100 000 bending repetitions (bending radius: 5 mm) confirm the ultrahigh mechanical stability of the TCO. The sheet resistance of flexible IZTO electrode layers is increased by 9%, from 17.42 to 19.12 Ω sq−1. In addition, the impact of a large number of bending repetitions on film transmittance is minimal. The OPV shows ≈69% and ≈20% of its initial power conversion efficiency value after 100 000 bending repetitions for 1000 lx LED illumination and 1 sun conditions, respectively.

Improved mechanical stability of indium zinc tin oxide based flexible transparent electrode through interlayer treatment

AbstractDue to the significant growth of the market for numerous flexible electronic devices, demand for mechanically stable indium zinc tin oxide (IZTO) based flexible transparent electrodes has recently expanded substantially. So, we have attempted to increase the mechanical stability of an IZTO based flexible transparent electrode by forming an ultrathin interlayer of an organic semiconductor polystyrene sulfonate doped polyaniline (PANI:PSS). According to the results of the systematic investigation, the PANI:PSS treated IZTO film can preserve 97.50% of its initial average transmittance (AVT) value (83.07%) after 20,000 bending cycles, but the bare IZTO film can retain only 89.00% of its initial AVT value (86.40%) after the same treatment. Furthermore, the PANI:PSS treatment has benefited in the reduction of IZTO film sheet resistance from 17.38 to 16.91 Ω/sq. Scanning electron microscopy images have indicated that the presence of a PANI:PSS interlayer on the IZTO film prevents the formation of fractures on the inorganic IZTO layer when mechanical stress is applied.

In-Zn-Sn-O thin film based transistor with high-k HfO2 dielectric

Indium zinc tin oxide (IZTO) semiconducting thin films have been investigated as active channel layers for thin-film transistor (TFT) applications. The IZTO layer was deposited by radio frequency magnetron sputtering (RF-MS) using a sintered IZTO ceramic target with an In:Zn:Sn metal atomic ratio of 40:50:10 on the HfO2 layer either deposited using an atomic layer deposition (ALD) or RF-MS. The annealing treatments after IZTO and HfO2 film depositions were performed in air using a tube furnace and in an oxygen atmosphere using rapid thermal annealing at 400 °C, respectively. Optical transparency measured by UV-Vis spectroscopy showed that the HfO2 films deposited by either RF-MS or ALD were transparent in the visible region and had a similar band gap energy of about 4.9 eV. Electrical characteristics of IZTO based TFT were comparatively evaluated for the samples with IZTO/ALD or RF-MS HfO2/n++-Si structure. The IZTO TFT sample with 60 nm-thick HfO2 deposited by ALD had an on/off current ratio value of 7.0 × 106 and a field-effect mobility value of 6.2 cm2/Vs, which was superior to that with RF-MS deposited HfO2.

Highly stable Ba-addition InZnSnO channels of light emitting transistors and thin film transistors

In this study, we investigate the characteristics of barium-addition indium-zinc-tin-oxide (B–IZTO) channels fabricated by the co-sputtering of barium-tin-oxide and indium-zinc-tin-oxide (IZTO) targets for the operation of thin film transistors (TFTs) and light emitting transistors (LETs). The X-ray photoelectron spectroscopy (XPS) analysis verifies that increasing the BaSnO3 sputtering power significantly decreases the concentration of oxygen vacancy from 35.0% to 16.3%. In addition, increasing the Ba concentration in the B–IZTO films increases the average transmittance of the B–IZTO channel in the visible light region (400–800 nm) from 86.7% to 88.3%, and the electrical resistivity from 84.3 to 5408 Ω∙cm, respectively. We find that the appropriate composition of Ba in the IZTO channels greatly improves the subthreshold swing (SS), the stability against the negative bias illumination stress (NBIS) of the B–IZTO channels-based TFTs. As the Ba content of the IZTO channel layer increases, SS decreases from 0.49 to 0.13 V/decade and the threshold voltage shift (ΔVTH) by NBIS reduces from − 13.1 to − 5.07 V, respectively. In the case of the B–IZTO-based LET with the highest Ba content, the device has the lowest light turn on voltage (VON) of 1.84 V, and shows the maximum brightness of 1.53 × 104 cd/m2. In this study, we confirm that the addition of Ba in the IZTO effectively suppresses the oxygen vacancies in the IZTO channel, resulting in the enhanced stability of the B–IZTO-based TFTs, and improves the performance of the B–IZTO-based LETs.

Low-Temperature Deposition of Transparent Conducting Films Applied to Flexible Electrochromic Devices.

Here, we compare two different transparent conducting oxides (TCOs), namely indium tin oxide (ITO) and indium zinc tin oxide (IZTO), fabricated as transparent conducting films using processes that require different temperatures. ITO and IZTO films were prepared at 230 °C and at room temperature, respectively, on glass and polyethylene terephthalate (PET) substrates using reactive magnetron sputtering. Electrochromic WO3 films deposited on ITO-based and IZTO-based ECDs using vacuum cathodic arc plasma (CAP) were investigated. IZTO-based ECDs have higher optical transmittance modulation, ΔT = 63% [from Tbleaching (90.01%) to Tcoloration (28.51%)], than ITO-based ECDs, ΔT = 59%. ECDs consisted of a working electrochromic electrode (WO3/IZTO/PET) and a counter-electrode (Pt mesh) in a 0.2 M LiClO4/perchlorate (LiClO4/PC) liquid electrolyte solution with an active area of 3 cm × 4 cm a calculated bleaching time tc of 21.01 s and a coloration time tb of 4.7 s with varying potential from −1.3 V (coloration potential, Vc) to 0.3 V (bleaching potential, Vb).

Boosting carrier mobility and stability in indium\u2013zinc\u2013tin oxide thin-film transistors through controlled crystallization

We investigated the effect of film thickness (geometrical confinement) on the structural evolution of sputtered indium-zinc-tin oxide (IZTO) films as high mobility n-channel semiconducting layers during post-treatment at different annealing temperatures ranging from 350 to 700 °C. Different thicknesses result in IZTO films containing versatile phases, such as amorphous, low-, and high-crystalline structures even after annealing at 700 °C. A 19-nm-thick IZTO film clearly showed a phase transformation from initially amorphous to polycrystalline bixbyite structures, while the ultra-thin film (5 nm) still maintained an amorphous phase. Transistors including amorphous and low crystalline IZTO films fabricated at 350 and 700 °C show reasonable carrier mobility (µFE) and on/off current ratio (ION/OFF) values of 22.4–35.9 cm2 V−1 s−1 and 1.0–4.0 × 108, respectively. However, their device instabilities against positive/negative gate bias stresses (PBS/NBS) are unacceptable, originating from unsaturated bonding and disordered sites in the metal oxide films. In contrast, the 19-nm-thick annealed IZTO films included highly-crystalline, 2D spherulitic crystallites and fewer grain boundaries. These films show the highest µFE value of 39.2 cm2 V−1 s−1 in the transistor as well as an excellent ION/OFF value of 9.7 × 108. Simultaneously, the PBS/NBS stability of the resulting transistor is significantly improved under the same stress condition. This promising superior performance is attributed to the crystallization-induced lattice ordering, as determined by highly-crystalline structures and the associated formation of discrete donor levels (~ 0.31 eV) below the conduction band edge.

Effects of Zn Ratio Tuning on the Structural and Transport Properties of Amorphous Indium Zinc Tin Oxide Thin Films

In this study, various indium zinc tin oxide (IZTO) films were fabricated using co-sputtering to explore amorphous transparent conducting oxides as alternatives to crystalline indium tin oxide (ITO). Various Zn ratios were tuned to study their effects on the structural evolution of IZTO. Amorphous IZTO (aIZTO) films were obtained when the Zn concentration was higher than approximately 17 at.%. X-ray diffraction and transmission electron microscopy analyses indicated that amorphous structures were formed due to the high crystallization temperatures of IZTO and nanocrystalline In2Zn5O8, which also caused aIZTO to exhibit small band gaps. On average, 87% transmittance was achieved in the visible light range. The aIZTO films had substantially higher transmittance in the infrared region than the ITO films did. Samples with Zn ratios between approximately 17 at.% and 27 at.% exhibited resistivity (approximately 3 × 10−4 Ω-cm), mobility (7 cm2 V−1 s−1), and carrier concentrations (4 × 1021 cm−3) comparable to those of crystalline ITO. Thus, the aIZTO films are promising alternative TCO materials. The mechanisms of competition between the crystallinity, oxygen deficiency, high-mobility In2Zn5O8, and electron and hole generation rates were applied to shed light on the excellent electrical and transport properties of aIZTO films.

Electrical and Optical Properties of Amorphous Indium-Zinc-Tin Oxide Thin Films: Oxygen Flow Dependence

In this study, the electrical and the optical properties of the amorphous indium-zinc-tin oxide (IZTO) thin films that had been grown using a cosputtering system were investigated as a function of the oxygen flow rate during growth. The optical constants of the IZTO thin films were obtained by applying the Drude and the parametric optical constant models to the ellipsometric angles, Ψ and Δ. We estimated the optical gap energies of the IZTO thin films from their absorption coefficients (α). The Drude tail amplitudes in the optical spectra were found to decrease under the deposition condition of increasing oxygen flow. The resistivity of the IZTO films was measured to be as low as 0.547 mΩ·cm at an oxygen flow rate of 0.3 sccm. Further, the Hall carrier concentrations and the mobilities were measured. We determined the effective masses of the IZTO thin films by using a combination of their optical and electrical parameters. The effective mass of the amorphous IZTO thin films decreased from 0.61 to 0.44 m0 as the oxygen gas flow rate was increased. Assuming a linear dependence of the effective mass on the carrier concentration, we estimated the effective mass at the conduction band minimum. The optically and electrically measured resistivities and mobilities of the amorphous IZTO thin films were equal because the films were free of grain boundaries; therefore, no scattering of free carriers from such grain boundaries had to be considered.

Indium-Zinc-Tin-Oxide Film Prepared by Reactive Magnetron Sputtering for Electrochromic Applications.

This paper reports on the fabrication of indium-zinc-tin-oxide (IZTO) transparent conductive film deposited by direct current (DC) reactive magnetron sputtering. The electrical, structural, and optical properties of IZTO film were investigated by Hall measurement, X-ray diffraction (XRD), and optical transmission spectroscopy with various sputtering powers. The IZTO film prepared used power at 100 W showed the lowest resistivity of 5.2 × 10−4 Ω cm. To accomplish rapid switching and high optical modulation, we have fabricated an electrochromic device (ECD) consisting of an working electrode (WO3 electrode film deposited on IZTO/ITO/glass) and a counter-electrode (Pt mesh) in 0.2 M LiClO4/PC liquid solution. The device demonstrated an optical contrast of 44% and switching times of 4.6 s and 8.1 s for the coloring and bleaching state, respectively, at the wavelength of 550 nm.

Organic Photovoltaics with Non-Stoichiometric InZnSnO Thin Film Cathodes

Non-stoichiometric indium zinc tin oxide (IZTO) thin films were deposited onto glass substrates at 400 °C by DC magnetron sputtering using non-stoichiometric (In0.5Zn0.25−xSn0.25+xO1.5 and In0.4Zn0.3−xSn0.3+xO1.5, where x = ±0.05) IZTO ceramic targets. After deposition, all of the films were given annealing treatment at 450 °C in argon. The crystallization behavior was examined by X-ray diffraction, while the optical properties were measured by ultraviolet-visible spectroscopy, in which the average transmittance values higher than 80% were observed from all films. The minimum resistivity of approximately 6.3 × 10−4 Ω·cm was observed from the Sn-rich In0.5Zn0.2Sn0.3O1.5 film. The resistivity values of Sn-rich IZTO thin films were a little smaller than those of Zn-rich IZTO films. An OPV cell with the so-called inverted structure was fabricated using various IZTO films deposited under optimized conditions as the cathode electrode. It was found that the solar cell efficiency could reach up to 7.9% which is the same with the OPV cell with conventional ITO film.

Synthesis of IZTO(Indium Zinc Tin Oxide) particle by spray pyrolysis and post-heat treatment and characterization of deposited IZTO film

The micron-sized indium zinc tin oxide (IZTO) particles were prepared by spray pyrolysis from aqueous precursor solution for indium, zinc, and tin and organic additives such as citric acid (CA) and ethylene glycol (EG) were added to aqueous precursor solution for indium, zinc, and tin. The obtained IZTO particles prepared by spray pyrolysis from the aqueous solution without organic additives had spherical and filled morphologies, whereas the IZTO particles obtained with organic additives had more hollow and porous morphologies. The micron-sized IZTO particles with organic additives were changed fully to nano-sized IZTO particles, whereas the micron-sized IZTO particles without organic additives were not changed fully to nano-sized IZTO particle after post-treatment at 700 °C for 2 hours and wet-ball milling for 24 hours. Surface resistances of micron-sized IZTO’s before post-heat treatment and wet-ball milling were much higher than those of nano-sized IZTO’s after post-heat treatment and wet-ball milling. From IZTO with composition of 80 wt. % In2O3, 10 wt. % ZnO, and 10 wt. % SnO2 which showed a smallest surface resistance IZTO after post-heat treatment and wet-ball milling, thin films were deposited on glass substrates by pulsed DC magnetron sputtering, and the electrical and optical properties were investigated.

Effects of cation compositions on the electronic properties and optical dispersion of indium zinc tin oxide thin films by electron spectroscopy

The electronic properties and optical dispersion of indium zinc tin oxide (IZTO) films with different cation compositions were investigated by reflection electron energy loss spectroscopy (REELS). The REELS spectra of IZTO films revealed that the band gap varied with different Sn/Zn ratios and In content. The optical properties were examined with REELS data using Tougaard–Yubero model and the results were compared with the envelope of the transmission spectra obtained using a UV-spectrometer. The dispersion behavior of the refractive index from REELS results was studied in terms of the single-oscillator Wemple–DiDomenico model. The results showed that the different compositions of In/Zn/Sn caused a change in the dispersion parameters of IZTO thin films in contrast to the static values of refractive indices and dielectric constant which remained the same. Our work demonstrated that REELS is an efficient tool to study the optical properties of a material by obtaining the optical parameters.

Transparent conducting indium zinc tin oxide thin films with low indium content deposited by radio frequency magnetron sputtering

Indium zinc tin oxide (IZTO) thin films were deposited on glass substrate by radio frequency magnetron sputtering at various substrate temperatures. The indium content of the IZTO targets was reduced from 60at.% to 30at.% and replaced with equal amounts of zinc and tin (20, 25, 30, and 35at.%). The crystallinity of the as-deposited films improved with increasing substrate temperature. For all IZTO films, the onset of crystallization began at above 100°C. The IZTO films deposited at higher substrate temperature showed better optical transmittance and lower electrical resistivity than those deposited at lower temperatures. The minimum electrical resistivity of approximately 8.0×10−4Ω·cm was observed in the IZTO films prepared deposited at 400°C from targets containing 20at.% Zn and 20at.% Sn. The optical transmittance was above 80% for all IZTO films. On the other hand, higher co-doping resulted in amorphous films, which slightly impaired the electrical properties. The deterioration in the electrical properties of IZTO films, however, was compensated for by the higher optical transparency. Therefore, reduced-indium IZTO films are promising alternatives for some transparent conducting oxide applications.

Device Performances of Organic Light-Emitting Diodes with Indium Tin Oxide, Gallium Zinc Oxide, and Indium Zinc Tin Oxide Anodes Deposited at Room Temperature

Thin films of Indium tin oxide (ITO), Gallium zinc oxide (GZO), and Indium zinc tin oxide (IZTO) were deposited on glass substrates by pulsed direct current magnetron sputtering at room temperature. The structural, optical, and electrical properties of the films were investigated towards evaluating their applications as flexible anodes. IZTO films exhibited the lowest resistivity (6.3 x 10(-4) Omega cm). Organic light-emitting diodes (OLEDs) were fabricated using the ITO, GZO, and IZTO films as anode layers. The turn-on voltages at a current density of 4.5 mA/cm2, 5.5 mA/cm2, 6.5 mA/cm2 were 5.5 V, 13.7 V, and 4.7 V for the devices with ITO, GZO, and IZTO anodes, respectively. The best performance was observed with the IZTO film, indicating its suitability as an alternative material for conventional ITO anodes used in OLEDs and flexible displays.

Oxygen effect of transparent conducting amorphous Indium Zinc Tin Oxide films on Polyimide substrate for flexible electrode

This paper discusses the effect of oxygen on the transparent conducting properties and mechanical durability of the amorphous indium zinc tin oxide (IZTO) films. IZTO films deposited on flexible clear polyimide (PI) substrate using pulsed direct current (DC) magnetron sputtering at room temperature under various oxygen partial pressures. All IZTO films deposited at room temperature exhibit an amorphous structure. The electrical and optical properties of the IZTO films were sensitively influenced by oxygen partial pressures. At optimized deposition condition of 3.0% oxygen partial pressure, the IZTO film shows the lowest resistivity of 6.4×10−4Ωcm, high transmittance of over 80% in the visible range, and figure of merit value of 3.6×10−3Ω−1 without any heat controls. In addition, high work function and good mechanical flexibility of amorphous IZTO films are beneficial to flexible applications. It is proven that the proper oxygen partial pressure is important parameter to enhance the transparent conducting properties of IZTO films on PI substrate deposited at room temperature.

Effects of gas environment on electronic and optical properties of amorphous indium zinc tin oxide thin films

The electronic and optical properties of indium zinc tin oxide (IZTO) thin films grown under different gas environments were investigated by means of x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS). REELS spectra revealed that IZTO thin films under argon mixed with oxygen had band gaps of 3.07 eV before annealing and 3.46 eV after annealing at 350 °C in air. Meanwhile, the band gap for IZTO thin film grown under oxygen mixed with water and annealed at 350 °C in air was 3.26 eV. Band gaps obtained from REELS spectra are consistent with the optical band gaps obtained using UV-spectrometry. The REELS spectra were quantitatively analyzed based on comparison of the effective cross section for inelastic electron scattering in the REELS experiment to determine the dielectric function and transmittance of the IZTO thin films. It was found that amorphous IZTO films grown under argon mixed with oxygen followed by annealing at 350 °C exhibit higher optical transmittance in the visible-light region, higher carrier mobility, and a high on–off current ratio.

Enhanced performance in polymer light emitting diodes using an indium–zinc–tin oxide transparent anode by the controlling of oxygen partial pressure at room temperature

The amount of indium in indium zinc tin oxide (IZTO) was reduced by over 20% by manufacturing an IZTO target containing ZnO for application as the transparent conducting oxide (TCO) anode of polymer light emitting diodes (PLEDs). The IZTO target was manufactured with the composition In2O3 (70 at%)–ZnO (15 at%)–SnO2 (15 at%), and IZTO films were formed at room temperature using a pulsed DC magnetron sputtering system at oxygen partial pressures of 0–4%. The optical and electrical properties of the IZTO films and the device performance of PLEDs with IZTO film were characterized. Amorphous IZTO films prepared at an oxygen partial pressure of 3% showed the best properties. The resistivity, mobility, transmittance, figure of merit and work function of the IZTO film were 5.6 × 10−4 Ω cm, 44.59 cm2 V s−1, 81% (visible region), 3.0 × 10−3 ohm−1, and 5.56 eV, respectively. The PLEDs with the IZTO film deposited under the optimum conditions showed the maximum brightness and the maximum luminance efficiency of 23 485 cd cm−2 and 2.29 cd A−1, respectively, which showed a 21% enhancement in device performance compared to PLEDs with commercial ITO film. In addition, the stability of the fabricated device was improved.

Charge‐Generating Mode Control in High‐Performance Transparent Flexible Piezoelectric Nanogenerators

AbstractIn this work, we demonstrate the mode transition of charge generation between direct‐current (DC) and alternating‐current (AC) from transparent flexible (TF) piezoelectric nanogenerators (NGs), which is dependent solely on the morphology of zinc oxide (ZnO) nanorods without any use of an AC/DC converter. Tilted ZnO nanorods grown on a relatively low‐density seed layer generate DC‐type piezoelectric charges under a pushing load, whereas vertically aligned ZnO nanorods on a relatively high‐density seed layer create AC‐type charge generation. The mechanism for the geometry‐induced mode transition is proposed and characterized. We also examine the output performance of TF‐NGs which employ an indium zinc tin oxide (IZTO) film as a TF electrode. It is demonstrated that an IZTO film has improved electrical, optical, and mechanical properties, in comparison with an indium tin oxide (ITO) film. Enhanced output charge generation is observed from IZTO‐based TF‐NGs when TF‐NGs composed of only ITO electrodes are compared. This is attributed to the higher Schottky barrier and the lower series resistance of the IZTO‐based TF‐NGs. Thus, by using IZTO, we can expect TF‐NGs with superior mechanical durability and power generating performance.