Indium Zinc Tin Oxide Research Articles

Highly Stable, Solution‐Processed Ga‐Doped IZTO Thin Film Transistor by Ar/O2 Plasma Treatment

AbstractThe effects of gallium doping into indium–zinc–tin oxide (IZTO) thin film transistors (TFTs) and Ar/O2 plasma treatment on the performance of a‐IZTO TFT are reported. The Ga doping ratio is varied from 0 to 20%, and it is found that 10% gallium doping in a‐IZTO TFT results in a saturation mobility (µsat) of 11.80 cm2 V−1 s−1, a threshold voltage (Vth) of 0.17 V, subthreshold swing (SS) of 94 mV dec−1, and on/off current ratio (Ion/Ioff) of 1.21 × 107. Additionally, the performance of 10% Ga‐doped IZTO TFT can be further improved by Ar/O2 plasma treatment. It is found that 30 s plasma treatment gives the best TFT performances such as µsat of 30.60 cm2 V−1 s−1, Vth of 0.12 V, SS of 92 mV dec−1, and Ion/Ioff ratio of 7.90 × 107. The bias‐stability of 10% Ga‐doped IZTO TFT is also improved by 30 s plasma treatment. The enhancement of the TFT performance appears to be due to the reduction in the oxygen vacancy and OH concentrations.

Low-temperature reducible particle-free screen-printable silver ink for the fabrication of high conductive electrodes

In this contribution, screen printing of aqueous based particle-free silver ink is addressed using combustion chemistry, where inks embody a redox mixture of silver nitrate and citric acid in the presence of a binder, sodium-carboxymethylcellulose. The exothermic reaction at ~ 176 °C results in the formation of pure silver. Screen-printing process is optimized for three different silver loadings (14%, 18% and 22%) in ink. In depth rheological study of the inks reveals thixotropic nature and the ink with 18% of silver possessing a viscosity of 328 Pa .s has a recovery rate of 84% at 110 s with a shear rate of 1 s−1. The deposited silver films (~ 3 µm thick) on both rigid-glass and flexible-polyamide substrates have shown an electrical conductivity of 4.2 × 106 S m−1 and 2.6 × 106 S m−1 respectively. Film adhesion on glass substrates categorized under 3B as per ASTM D-3359. Present screen-printed silver films find their application as a gate electrode in thin film transistors (TFTs). The TFTs comprising of indium zinc tin oxide–semiconductor and sodium β -alumina dielectric with screen-printed silver as a gate electrode exhibited the saturation mobility, on:off ratio and threshold voltage of 0.88 cm2 V−1 s−1, 102 and ~ 0.3 V respectively.

Highly efficient flexible organic light-emitting diodes based on a high-temperature durable mica substrate

Abstract Muscovite mica is expected to show great potential in flexible optoelectronics due to its superb temperature tolerance, high transmittance, chemical stability, and mechanical durability. This flexible substrate produces sputtered transparent conducting electrodes (TCEs) with excellent film quality with high transmittance and conductivity. In this study, a designed composite TCE consisting of aluminum-doped zinc oxide (AZO) and indium tin oxide (ITO) is proposed to simultaneously maximize flexibility and conductivity. Blue-, green-, and red-emitting flexible organic light-emitting diodes (FOLEDs) using composite TCEs on mica exhibited satisfactory performance with maximum respective electroluminescence efficiencies of 18.1% (38.7 cd/A), 18.7% (66.2 cd/A), and 13.3% (22.2 cd/A). Furthermore, the green-emitting FOLEDs were modified to construct tandem FOLEDs, giving a higher peak efficiency of 27.9% (93.3 cd/A) and saturated green emission. These results can serve as a useful reference for future work on composite TCEs on mica for FOLEDs in display and lighting applications.

Efficient semi-transparent perovskite solar cells with a novel indium zinc tin oxide top electrode grown by linear facing target sputtering

We propose that an indium zinc tin oxide electrode grown by linear facing target sputtering without additional thermal treatment can effectively act as an efficient semi-transparent top electrode for high-performance semi-transparent hybrid perovskite solar cells. The semi-transparent perovskite solar cells using an indium zinc tin oxide electrode as a novel top electrode achieves a power conversion efficiency of 12.85%, similar to that of an opaque electrode-based device of 13.48%. More importantly, by adjusting the perovskite thickness, a power conversion efficiency of 8.306% is obtained at an average visible transmittance of 33.9%, thus well supporting that the indium zinc tin oxide electrode can be considered to be an advanced and efficient semi-transparent top electrode for the fabrication of building integrated photovoltaics with high efficiency and good transparency.

Fabrication of Robust Nanoscale Contact between a Silver Nanowire Electrode and CdS Buffer Layer in Cu(In,Ga)Se2 Thin-film Solar Cells.

Silver nanowire transparent electrodes have been employed as window layers for Cu(In,Ga)Se2 thin-film solar cells. Bare silver nanowire electrodes normally result in very poor cell performance. Embedding or sandwiching silver nanowires using moderately conductive transparent materials, such as indium tin oxide or zinc oxide, can improve cell performance. However, the solution-processed matrix layers can cause a significant number of interfacial defects between transparent electrodes and the CdS buffer, which can eventually result in low cell performance. This manuscript describes how to fabricate robust electrical contact between a silver nanowire electrode and the underlying CdS buffer layer in a Cu(In,Ga)Se2 solar cell, enabling high cell performance using matrix-free silver nanowire transparent electrodes. The matrix-free silver nanowire electrode fabricated by our method proves that the charge-carrier collection capability of silver nanowire electrode-based cells is as good as that of standard cells with sputtered ZnO:Al/i-ZnO as long as the silver nanowires and CdS have high-quality electrical contact. The high-quality electrical contact was achieved by depositing an additional CdS layer as thin as 10 nm onto the silver nanowire surface.

The impact of plasma-enhanced atomic layer deposited ZrSiOx insulators on low voltage operated In-Sn-Zn-O thin film transistors

Abstract We deposited Zr silicate by plasma-enhanced atomic layer deposition (PEALD) and investigated its gate insulator performance in indium-tin-zinc oxide (ITZO) thin film transistors (TFTs). Deposited Zr silicate had the desired characteristics of both ZrO 2 , a high-k dielectric, and SiO 2 . The drawbacks of ZrO 2 thin film can be compensated by employing Zr silicate thin film because the latter has a moderate dielectric constant of 8.4, stoichiometric chemistry, smooth surface, and a low leakage current. Zr silicates as gate insulators may play important roles to reduce coulomb scattering and decrease charge trap density, resulting in high electrical performance and appropriate device stability when used in ITZO TFTs.

9‐1: Invited Paper: Metal‐oxide readout electronics based on Indium‐Gallium‐Zinc‐Oxide and Indium‐Tin‐Zinc‐Oxide for in‐panel fingerprint detection application

This work describes integrated readout electronics for on‐panel fingerprint detection, focusing on two key building blocks: charge sense amplifier (CSA) and analog‐to‐digital converter (ADC). The CSA has been realized in a dual‐gate self‐aligned IGZO thin‐film transistor (TFT) technology with channel length downsizing to 3µm, enabling 1.3mm bezel size for the peripheral readout electronics and 1fps readout of a 1‐Mpixel 500dpi sensor array. The ADC has been realized in two different transistor technologies, IGZO and Indium‐Tin‐Zinc‐Oxide (ITZO). The ITZO ADC achieves a sampling rate of 1kS/s, which is 7.5x faster compared to the IGZO ADC, due to the larger mobility of ITZO.

High Performance of a‐IZTO TFT by Purification of the Semiconductor Oxide Precursor

AbstractThe effect of purification of oxide semiconductor precursor on the performance of amorphous indium–zinc–tin oxide (a‐IZTO) thin‐film transistors (TFT) using a high‐k zirconium oxide (ZrOx) gate insulator is reported. By purification of IZTO precursor, the saturation mobility (µsat) of the IZTO TFT increases from 2.84 to 9.50 cm2 V−1 s−1, threshold voltage (VTH) decreases from 0.63 to 0.51 V, subthreshold swing (SS) decreases from 169 to 87 mV dec−1, hysteresis voltage (VH) reduces from 0.05 to 0 V, and an ON/OFF current ratio (ION/IOFF) increases from ≈107 to ≈108. These improvements are due to the reduction in the impurities and oxygen vacancies at the bulk of IZTO and a‐IZTO/ZrOx interface as well. The significant reduction of broad absorbance peak centered at 553 nm can be found by purification, which is direct evidence of the reduction of the impurity concentration in the metal oxide precursor solution.

The Characteristics of Transparent Non-Volatile Memory Devices Employing Si-Rich SiOX as a Charge Trapping Layer and Indium-Tin-Zinc-Oxide

We fabricated the transparent non-volatile memory (NVM) of a bottom gate thin film transistor (TFT) for the integrated logic devices of display applications. The NVM TFT utilized indium–tin–zinc–oxide (ITZO) as an active channel layer and multi-oxide structure of SiO2 (blocking layer)/Si-rich SiOX (charge trapping layer)/SiOXNY (tunneling layer) as a gate insulator. The insulators were deposited using inductive coupled plasma chemical vapor deposition, and during the deposition, the trap states of the Si-rich SiOx charge trapping layer could be controlled to widen the memory window with the gas ratio (GR) of SiH4:N2O, which was confirmed by fourier transform infrared spectroscopy (FT-IR). We fabricated the metal–insulator–silicon (MIS) capacitors of the insulator structures on n-type Si substrate and demonstrated that the hysteresis capacitive curves of the MIS capacitors were a function of sweep voltage and trap density (or GR). At the GR6 (SiH4:N2O = 30:5), the MIS capacitor exhibited the widest memory window; the flat band voltage (ΔVFB) shifts of 4.45 V was obtained at the sweep voltage of ±11 V for 10 s, and it was expected to maintain ~71% of the initial value after 10 years. Using the Si-rich SiOX charge trapping layer deposited at the GR6 condition, we fabricated a bottom gate ITZO NVM TFT showing excellent drain current to gate voltage transfer characteristics. The field-effect mobility of 27.2 cm2/Vs, threshold voltage of 0.15 V, subthreshold swing of 0.17 V/dec, and on/off current ratio of 7.57 × 107 were obtained at the initial sweep of the devices. As an NVM, ΔVFB was shifted by 2.08 V in the programing mode with a positive gate voltage pulse of 11 V and 1 μs. The ΔVFB was returned to the pristine condition with a negative voltage pulse of −1 V and 1 μs under a 400–700 nm light illumination of ~10 mWcm−2 in erasing mode, when the light excites the electrons to escape from the charge trapping layer. Using this operation condition, ~90% (1.87 V) of initial ΔVFB (2.08 V) was expected to be retained over 10 years. The developed transparent NVM using Si-rich SiOx and ITZO can be a promising candidate for future display devices integrating logic devices on panels.

Nonthermal crystal bridging of ZnO nanoparticles by nonequilibrium excitation reaction of electrons and plasma without cross-linking agent on plastic substrate

Conductive ceramic films, such as indium tin oxide (ITO) and zinc oxide (ZnO) thin films, are expected to be used as core semiconducting materials for applications for the Internet of Things (IoT). In this study, we focused on a nonequilibrium excitation reaction field as a bottom-up architecture, and we successfully found the basis of a technology for fabricating the above films using a plasma atmosphere and an electron beam that uniformly emits electrons within a plane as a nonequilibrium reaction field. In particular, the ZnO thin film obtained in this study exhibited good electrical properties, such as a high Hall mobility of 128.3 cm2/V, even though it was formed on a polyethylene terephthalate (PET) film substrate at room temperature. This achievement may contribute to clarifying the mechanism behind the fabrication of highly functional oxide thin films by a two-dimensional simple process without thermal treatment of the substrate during the film formation. Moreover, this technique will also enable us to provide elements for next-generation nanodevices in IoT by controlling the surface and interface of nanostructures as well as highly functional properties using complexes of metals, ceramics, and semiconductors.

High-Performance Thin-Film Transistors of Quaternary Indium-Zinc-Tin Oxide Films Grown by Atomic Layer Deposition.

A new deposition technique is required to grow the active oxide semiconductor layer for emerging oxide electronics beyond the conventional sputtering technique. Atomic layer deposition (ALD) has the benefits of versatile composition control, low defect density in films, and conformal growth over a complex structure, which can hardly be obtained with sputtering. This study demonstrates the feasibility of growing amorphous In-Zn-Sn-O (a-IZTO) through ALD for oxide thin-film transistor (TFT) applications. In the ALD of the a-IZTO film, the growth behavior indicates that there exists a growth correlation between the precursor molecules and the film surface where the ALD reaction occurs. This provides a detailed understanding of the ALD process that is required for precise composition control. The a-IZTO film with In/Zn/Sn = 10:70:20 was chosen for high-performance TFTs, among other compositions, regarding the field-effect mobility (μFE), turn-on voltage ( Von), and subthreshold swing (SS) voltage. The optimized TFT device with the a-IZTO film thickness of 8 nm revealed a high performance with a μFE of 22 cm2 V-1 s-1, Von of 0.8 V, and SS of 0.15 V dec-1 after annealing at 400 °C for 30 min. Furthermore, an emerging device such as a vertical channel TFT was demonstrated. Thus, the a-IZTO ALD process could offer promising opportunities for a variety of emerging oxide electronics beyond planar TFTs.

High-performance low voltage operation of indium zinc tin oxide thin film transistors using chemically derived sodium β-alumina dielectric

We present high performance, low voltage (≤ 3 V) operation of thin film transistors (TFTs) with indium zinc tin oxide (IZTO: In4Sn4ZnO15)-semiconductor. The film of IZTO was fabricated via low-temperature (200 °C) solution combustion processing without incorporating an external fuel. As 2-methoxyethanol is a widely used organic solvent due to its high dissolution capability, serve the purpose of both the solvent and the fuel. On quantification from the balanced redox reaction, 0.3% of 2-methoxyethanol assisted for the action of fuel and helped in the formation of metal oxide, and the rest (99.7%) served the purpose of being dissolution medium. The balanced redox chemistry yielded a significant fraction of (56.5%) metal oxide at 200 °C confirmed via high-resolution oxygen 1s spectrum. Further, the chemically derived thin film of sodium β-alumina with a dielectric constant of ~ 21, while annealing at 350 °C incorporated in the TFT for the realization of low voltage operation. The performance assessment is systematically carried out both silicon dioxide (SiO2) and sodium β-alumina and found that the TFTs with SiO2 and IZTO exhibited a saturation mobility (µsat), Ion/Ioff ratio and the threshold voltage (Vth) of 0.50 ± 0.02 cm2 V−1 s−1, 1.25 × 104 and 6.6 ± 0.79 V respectively. While changing the dielectric to sodium β-alumina presented a µsat, Ion/Ioff ratio and Vth of 4.21 ± 0.18 cm2 V−1 s−1, 1.4 × 102 and 0.47 ± 0.08 V respectively.

Effects of high-k gate dielectrics on the electrical performance and reliability of an amorphous indium-tin-zinc-oxide thin film transistor (a-ITZO TFT): an analytical survey.

This study is a numerical simulation obtained by using Silvaco Atlas software to investigate the effect of different types of dielectric layers, inserted between the channel and the gate, on the performance and reliability of an a-ITZO TFT. Replacing the SiO2 oxide layer with a high-k dielectric layer gives the concept of the electrical thickness, known by the equivalent oxide thickness (EOT) in which the physical thickness (PT) can be increased to improve the device reliability without increasing the effective thickness of the gate dielectric. A range of different high-k dielectric materials was suggested. For low-k SiO2 (k = 3.9), the electrical parameters extracted are: Ci = 3.45 × 10-8 F cm-2, Ion = 2.23 × 10-6 A, Ioff = 2.17 × 10-13 A, Ion/Ioff = 1.02 × 107, EOT = 100 nm, VT = -0.61 V, μFE = 29.75 cm2 V-1 s-1, SS = 7.91 × 10-2 V per decade and Von = -0.95 V. Replacing SiO2 by a high-k dielectric material, such as SrTiO3 (k = 300), leads to effects similar to the effects of reducing the physical thickness of the gate dielectric but without actually reducing this physical thickness. This allows improving the outputs of the a-ITZO TFT as it leads to an increase in Ci, Ion and Ion/Ioff to the values Ci = 2.66 × 10-6 F cm-2, Ion = 2.86 × 10-4 A, and Ion/Ioff = 8.80 × 109, respectively, and the decrease in EOT, Ioff, VT, μFE, SS and Von to the values EOT = 1.3 nm, Ioff = 3.25 × 10-14 A, VT = -0.428 V, μFE = 26.66 cm2 V-1 s-1, SS = 6.12 × 10-2 V per decade and Von = -0.75 V, respectively, without leakage effects.

Multiaxial and Transparent Strain Sensors Based on Synergetically Reinforced and Orthogonally Cracked Hetero‐Nanocrystal Solids

AbstractWearable strain sensors are widely researched as core components in electronic skin. However, their limited capability of detecting only a single axial strain, and their low sensitivity, stability, opacity, and high production costs hinder their use in advanced applications. Herein, multiaxially highly sensitive, optically transparent, chemically stable, and solution‐processed strain sensors are demonstrated. Transparent indium tin oxide and zinc oxide nanocrystals serve as metallic and insulating components in a metal–insulator matrix and as active materials for strain gauges. Synergetic sensitivity‐ and stability‐reinforcing agents are developed using a transparent SU‐8 polymer to enhance the sensitivity and encapsulate the devices, elevating the gauge factor up to over 3000 by blocking the reconnection of cracks caused by the Poisson effect. Cross‐shaped patterns with an orthogonal crack strategy are developed to detect a complex multiaxial strain, efficiently distinguishing strains applied in various directions with high sensitivity and selectivity. Finally, all‐transparent wearable strain sensors with Ag nanowire electrodes are fabricated using an all‐solution process, which effectively measure not only the human motion or emotion, but also the multiaxial strains occurring during human motion in real time. The strategies can provide a pathway to realize cost‐effective and high‐performance wearable sensors for advanced applications such as bio‐integrated devices.

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.

The influence of optical and recombination losses on the efficiency of thin-film solar cells with a copper oxide absorber layer

We presented the results of the calculations of optical and recombination losses in photoconductor layers on the basis of heterojunctions with copper oxide absorbing layers (CuO, Cu2O) and zinc magnesium oxide (ZMO) window layer. Aluminum-doped zinc oxide (AZO) and indium tin oxide (ITO) were used as the solar cell frontal contacts. The spectral dependences of the transmission coefficient of these devices were determined. The reflection of light from the boundary of two contacting materials and light absorption in the auxiliary layers of photoconductors were taken into account. The influence of optical and recombination losses on the internal and external quantum yield, short circuit current density, and maximum efficiency of solar cells are investigated. It has been established that the highest efficiency (η = 19.12%) is shown by the device with the structure of AZO/ZMO/CuO.

Direct Photopatterning of Solution–Processed Amorphous Indium Zinc Oxide and Zinc Tin Oxide Semiconductors—A Chimie Douce Molecular Precursor Approach to Thin Film Electronic Oxides

AbstractDirect photopatterning of indium zinc oxide (IZO) and zinc tin oxide (ZTO) semiconductors is realized using Schiff‐base complexes of indium, zinc, and tin(II) with methoxyiminopropionato ligands as precursors. These precursor complexes are stable under visible light, but they interestingly decompose in the UV region, thereby facilitating a site‐selective photopatterning and its subsequent conversion to the desired amorphous oxides. Thin film transistors (TFTs) with photopatterned IZO and ZTO layers exhibit high performance after post‐annealing at relatively low temperatures between 250 and 350 °C, with charge‐carrier mobilities (µsat) of 7.8 and 3.6 cm2 (V s)−1 for IZO and ZTO, respectively. The mechanism of the photodecomposition of the precursor films is studied by attenuated total reflectance–Infrared spectroscopy. Apart from the electrical characterization, the resultant UV‐patterned oxide thin films are characterized by transmission electron microscopy micrographs of focussed ion beam (FIB)‐prepared cross sections, atomic force microscopy, as well as Auger depth profiles. X‐ray photoelectron spectroscopy investigations elucidate the influence of surface hydroxylation on the TFT performance. The straightforward approach of facile precursor UV‐photopatterning demonstrates its potential feasibility as a low‐cost method toward integration of such solution–processed oxide films into large‐area electronics.

P‐15: The Use of Fluorination to Enhance the Performance and the Reliability of Elevated‐Metal Metal‐Oxide Thin‐Film Transistors

The effects of fluorination on elevated‐metal metal‐oxide (EMMO) thin‐film transistors (TFT) were investigated. Attributed to the effective passivation of defects in the metal oxide, both the scalability and the reliability were enhanced on fluorinated indium‐gallium‐zinc oxide (IGZO) and indium‐tin‐zinc oxide (ITZO) EMMO TFTs.

Fabrication of Zinc Oxide-Based Thin-Film Transistors by Radio Frequency Sputtering for Ultraviolet Sensing Applications.

In this study, zinc indium tin oxide thin-film transistors (ZITO TFTs) were fabricated by the radio frequency (RF) sputtering deposition method. Adding indium cations to ZnO by co-sputtering allows the development of ZITO TFTs with improved performance. Material characterization revealed that ZITO TFTs have a threshold voltage of 0.9 V, a subthreshold swing of 0.294 V/decade, a field-effect mobility of 5.32 cm2/Vs, and an on-off ratio of 4.7 × 105. Furthermore, an investigation of the photosensitivity of the fabricated devices was conducted by an illumination test. The responsivity of ZITO TFTs was 26 mA/W, with 330-nm illumination and a gate bias of -1 V. The UV-to-visible rejection ratio for ZITO TFTs was 2706. ZITO TFTs were observed to have greater UV light sensitivity than that of ZnO TFTs. We believe that these results suggest a significant step toward achieving high photosensitivity. In addition, the ZITO semiconductor system could be a promising candidate for use in high performance transparent TFTs, as well as further sensing applications.

Transparent and Flexible Zinc Tin Oxide Thin Film Transistors and Inverters using Low-pressure Oxygen Annealing Process

We report on the transparent and flexible enhancement-load inverters which consist of zinc tin oxide (ZTO) thin film transistors (TFTs) fabricated at low process temperature. To control the electrical characteristics of oxide TFTs by oxygen vacancies, we applied low-pressure oxygen rapid thermal annealing (RTA) process to our devices. When we annealed the ZTO TFTs in oxygen ambient of 2 Torr, they showed better electrical characteristics than those of the devices annealed in the air ambient of 760 Torr. To realize oxide thin film transistor and simple inverter circuits on flexible substrate, we annealed the devices in O2 of 2 Torr at 150 ◦ C and could achieve the decent electrical properties. When we used transparent conductive oxide electrodes such as indium zinc oxide (IZO) and indium tin oxide (ITO), our transparent and flexible inverter showed the total transmittance of ~ 68% in the visible range and the voltage gain of ~ 5. And the transition voltage in voltage transfer curve was located well within the range of operation voltage.