Indium Zinc Tin Oxide Thin Films Research Articles

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.

Physical property improvement of IZTO thin films using a hafnia buffer layer

Hafnia (HfO2) has excellent mechanical and chemical stability, good transmittance, high dielectric constant, and radiation resistance property; thus, it can prevent impurities from permeating into the depositing films. So, we deposited hafnia films with various thicknesses in the range of 0–60 nm on polyethylene naphthalate (PEN) substrates before depositing indium–zinc–tin oxide (IZTO) thin films on them using RF magnetron sputtering, and their structural, morphological, optical, and electrical properties were evaluated. All IZTO thin films were successfully deposited without cracks or pinholes and had amorphous structures. As the thickness of the hafnia film increased to 30 nm, the overall properties improved; a surface roughness of 2.216 nm, transmittance of 82.59% at 550 nm, resistivity of 5.66 × 10−4 Ω cm, sheet resistance of 23.60 Ω/sq, and figure of merit of 6.26 × 10−3 Ω−1 were realized. These results indicate that the structure and materials studied in this research are suitable for application in flexible transparent electronic devices such as organic light emitting diodes, liquid crystal displays, touch panels, and solar cells.

Synthetic analysis on the IZTO thin films deposited on various plastic substrates with the buffer layer

Buffer layers, such as SiO2, may prevent impurities from permeating into the depositing film. Thus, the effects of buffer layer thickness on indium-zinc-tin oxide (IZTO) thin films were investigated. IZTO thin films are applied to transparent conductive oxide, and SiO2 is used as a material for the buffer layer. Before depositing the IZTO by RF magnetron sputtering, the SiO2 buffer layers were deposited on different plastic substrates, such as polyether sulfone, polyethylene terephthalate, and polyethylene naphthalate (PEN), by plasma enhanced chemical vapor deposition. The resulting structural, morphological, electrical, and optical properties were measured and analyzed. By using the obtained values of the electrical and optical properties, the figure of merit for transparent devices designed by Haacke was calculated. As a result, we conclude that the IZTO thin film deposited on a PEN substrate with a 30 nm thick SiO2 buffer layer has the finest properties, which are a resistivity of 2.13 × 10−3 Ω-cm, sheet resistance of 8.875 Ω sq−1, Hall mobility of 5.99 cm2 V−1 s−1, carrier concentration of 3.671 × 1021 cm−3, and transmittance of 80.26% at 550 nm. In addition, the figure of merit calculated for this sample was 12.50 × 10−3/Ω. These results indicate that the proposed structure is suitable for flexible display devices and flexible solar cells.

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.

High Mobility Thin Film Transistors Based on Amorphous Indium Zinc Tin Oxide.

Top-contact bottom-gate thin film transistors (TFTs) with zinc-rich indium zinc tin oxide (IZTO) active layer were prepared at room temperature by radio frequency magnetron sputtering. Sintered ceramic target was prepared and used for deposition from oxide powder mixture having the molar ratio of In2O3:ZnO:SnO2 = 2:5:1. Annealing treatment was carried out for as-deposited films at various temperatures to investigate its effect on TFT performances. It was found that annealing treatment at 350 °C for 30 min in air atmosphere yielded the best result, with the high field effect mobility value of 34 cm2/Vs and the minimum subthreshold swing value of 0.12 V/dec. All IZTO thin films were amorphous, even after annealing treatment of up to 350 °C.

Tuning the physical properties of amorphous In-Zn-Sn-O thin films using combinatorial sputtering

Transparent conductive oxides and amorphous oxide semiconductors are important materials for many modern technologies. Here, we explore the ternary indium zinc tin oxide (IZTO) using combinatorial synthesis and spatially resolved characterization. The electrical conductivity, work function, absorption onset, mechanical hardness, and elastic modulus of the optically transparent (>85%) amorphous IZTO thin films were found to be in the range of 10-2415 S/cm, 4.6-5.3 eV, 3.20-3.34 eV, 9.0-10.8 GPa, and 111-132 GPa, respectively, depending on the cation composition and the deposition conditions. This study enables control of IZTO performance over a broad range of cation compositions.

Properties of IZTO Thin Films Deposited on PEN Substrates with Different Working Pressures

In this work, the properties of Indium-Zinc-Tin-Oxide (IZTO) thin films, deposited on polyethylene naphthalate (PEN) with a SiO₂ buffer layer, were analyzed with different working pressures. After depositing the SiO₂ buffer layer on PEN substrates by plasma-enhanced chemical vapor deposition (PECVD), the IZTO thin films were deposited by RF magnetron sputtering with 1 to 7-mTorr working pressure. All the IZTO thin films show an amorphous structure, regardless of the working pressure. The best morphological, electrical, and optical properties are obtained at 3-mTorr working pressure, with a surface roughness of 2.112-nm, a sheet resistance of 8.87-Ω/sq, and a transmittance at 550-nm of 88.44%. These results indicate that IZTO thin films deposited on PEN have outstanding electrical and optical properties, and the PEN plastic substrate is a suitable material for display devices.

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.

RF 마그네트론 스퍼터를 사용하여 증착한 IZTO 박막의 Zn/Sn 비율에 따른 효과

Indium Zinc Tin Oxide (IZTO) thin films were developed as an alternative to Indium Tin Oxide (ITO) thin films. ITO material which has been acknowledged with its low resistivity and optical transparency of 85-90% has been used as major transparent conducting oxide (TCO) materials. However, due to the limited source, high price, and instability problems at high temperature of indium, many researches has been focused on indium-saving TCO materials. Mason Group of Northwestern University was reported to expand the solubility limit up to 40% by co-doping with 1:1 ratio of Zn +2 and Sn +4 ions. In this study, the properties of IZTO thin films corresponding to Zn/Sn different ratio were investigated. In addition, the effect of substrate temperature variable to the structural, optical and electrical properties of IZTO thin films was investigated.

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.

Electrical and Optical Properties of IZTO Thin Film for OLED Anode

Indium Zinc Tin Oxide (IZTO) thin-films for OLED (organic light-emitting diode) anodes were prepared through a Facing Target Sputtering (FTS) system under various sputtering conditions. The FTS system has several advantages such as hetero-sputtering, low working pressure, and high plasma density. When two sheets of targets are installed on an FTS system, one of the targets is IZO (In2O3 90wt%, ZnO 10 wt%) and the other target is ITO (In2O3 90wt%, SnO2 10wt%). As-deposited IZTO thin-films were investigated by a UV/VIS spectrometer, an X-ray diffractometer (XRD), a Hall-Effect measurement system, and an atomic force microscope (AFM). The properties of the OLEDs were measured through a J-I-V measurement system. The IZTO thin-films that were deposited on glass substrate showed an average transmittance of over 80% in a visible range except for IZTO thin-film that was deposited under an O2 gas flow rate of 0.1 [sccm].

The Characteristics of IZTO Thin Films Prepared by FTS with a Hetero-Target at Various Substrate Temperatures

Indium zinc tin oxide (IZTO) thin films were prepared by a facing targets sputtering (FTS) system under various substrate temperature conditions, from R.T to 300°C. The dependence of their electrical, optical and structural properties on the substrate temperature was investigated by a Hall Effect measurement system, a UV/VIS spectrometer, an X-ray diffractometer (XRD) and an atomic force microscope (AFM). The X-ray diffraction measurements showed that amorphous IZTO films were formed regardless of substrate temperatures. The lowest value of the resistivity was 4.18 × 10−4 [Ω·cm] at a substrate temperature of 100°C. All the IZTO thin films deposited showed an average transmittance of over 80% in the visible range.

Electrical and optical properties of In–Zn–Sn–O thin film deposited on polymer substrates through facing targets co-sputtering system

The Indium Zinc Tin Oxide (IZTO) thin films for use as a transparent electrode in flexible display were deposited on polycarbonate (PC) and polyethersulfone (PES) and glass substrates at room temperature by facing targets sputtering (FTS). When two sheets of targets are installed on an FTS system, one of target is IZO and other is ITO. As a result, we could prepare the IZTO thin films with the resistivity of under 10 − 4 [Ω cm] and IZTO thin films deposited on PC, PES and glass substrate showed an average transmittance over 80% in visible range (400–800 nm) in all IZTO thin films except for IZTO thin film that was deposited in a filled chamber with pure Ar gas.

Dependence of electrical, optical, and structural properties on the thickness of IZTO thin films grown by linear facing target sputtering for organic solar cells

The dependence of electrical, optical, structural, and surface properties on the thickness of indium zinc tin oxide (IZTO) electrodes grown on glass substrates by linear facing target sputtering at room temperature was investigated. The sheet resistance of the IZTO films gradually decreased with increase in IZTO thickness, while the resistivity and transparency of the IZTO films were constant regardless of its thickness due to the complete amorphous structure of the IZTO electrodes. However, the absorption edge of the IZTO electrodes shifted to longer wavelengths with increase in thickness due to band gap narrowing caused by the effects of electron–electron and electron–impurity scattering. In addition, the performance of organic solar cells (OSCs) critically depends on the thickness of an IZTO anode electrode with different sheet resistance ( R sheet) and transparency. For a thin IZTO anode (thickness less than 440 nm), the power conversion efficiency (PCE) of the OSCs was mainly affected by the R sheet, for a thick IZTO electrode (thickness greater than 440 nm), on the other hand, the transparency affected the PCE of the OSCs. Despite the much lower R sheet of the 1025-nm-thick IZTO (8.86 Ω/square), the OSC showed a lower PCE (2.00%) than those with a 440-nm-thick IZTO electrode (PCE: 2.23%) due to decreased optical transparency in the wavelength region of 450–600 nm, which was the absorption region of the active materials.

Properties of IZTO Thin Films Prepared by Using a Hetero-Target Sputtering System

Indium zinc tin oxide (IZTO) thin lms were deposited on glass substrates at room temperature by using facing targets sputtering (FTS). The FTS system was designed to array two targets facing each other and to form high-density plasma between them. The FTS system is a heterotarget sputtering system. When two di erent kinds of targets are installed in the FTS system, one target is ITO (In2O3 90 wt%, SnO2 10 wt%) and the other target is IZO (In2O3 90 wt%, ZnO 10 wt%). The conductive and optical properties of the IZTO thin lm were determined for various DC powers and working pressures. Therefore, the IZTO thin lms were prepared with di erent DC powers and working pressures. As-deposited IZTO thin lms were investigated by using a UV/VIS spectrometer, an X-ray di ractometer, a Hall-e ect measurement system and an atomic force microscope. All IZTO thin lms deposited on glass substrates showed an average of transmittance over 80 % in the visible range (400 800 nm), except the IZTO thin lm deposited at an O2 gas ow rate of 0.1 sccm. We could obtain IZTO thin lms with a low value of resistivity of 4.99 10 4 [ -cm] at an O2 gas ow rate of 0.4 sccm.