IZO Thin-film Transistors Research Articles

A 65-dB SNDR Continuous-Time Delta-Sigma ADC Integrated by IZO Thin-Film Transistors

A 65-dB SNDR Continuous-Time Delta-Sigma ADC Integrated by IZO Thin-Film Transistors

P‐7: Enhanced Visible Light Response of Amorphous InZnO Thin‐Film Transistors by Hydrogen Doping via Al2O3/SiO2 Gate Dielectric

Enhancement of visible light response in InZnO (IZO) thin‐film transistors (TFTs) by hydrogen doping via Al2O3/SiO2 dielectric layer is investigated. The IZO TFTs with Al2O3/SiO2 dielectric show better visible light detection performance due to the introduction of subgap states by hydrogen doping. The photocurrent, photoresponsivity, detectivity, and external quantum efficiency of the device to blue light are respectively improved from 4.94 × 10−7 A to 1.97 × 10−6 A, 4.93 A/W to 19.71 A/W, 2.70 × 1012 Jone to 5.77×1012 Jone, and 13.60 to 54.32 after hydrogen doping. The persistent photoconductivity effect is also eliminated by applying a positive gate pulse voltage.

The impact of nickel doping on metal-oxide network in solution-processed indium zinc oxide transistors

Solution-processed nickel zinc oxide (IZO) thin-film transistors (TFTs) are of great interest as core elements for future display technology based on the low-cost manufacture. It still remains a challenge to ensure stability in the off-current state of IZO using a dopant that is more resource-friendly than Ga in solution processing. In this study, we suggest a solution-based doping process of the IZO semiconductors with a Ni carrier suppressor and investigated the effects of Ni on their transistor operation. Owing to similar size of Ni2+ to Zn2+, an appropriate concentration of Ni partially substituted Zn sites and the strong bonding force of Ni with O reduces hydroxide groups on the surface bonded to Zn, whereas excess Ni addition rather inhibited the formation of smooth thin film. The resulting Ni-doped IZO TFT devices from an optimized Ni concentration exhibited higher performances with significantly reduced off-state currents while maintaining high on-state currents, compared to IZO TFTs. This approach enriches the current family of solution-processed metal oxide semiconductors by providing another option for resource-friendly carrier suppressor, which can contribute to the inexpensive and simple solution process for fabricating TFTs.

Electrical Performance Enhancement of Fully Solution-processed Amorphous In-Zn-O Thin-Film Transistor via Argon Plasma Treatment

Amorphous oxide semiconductors are intensively studied nowadays due to its excellent material characteristics, such as high mobility, high optical transparency, large area uniformity, and low processing temperature which enable flexible device application [1]. Solution approach is a promising method over conventional vacuum process, because of its simplicity and versatility with high material utilization which can minimize fabrication cost [2]. To optimize for application in flexible substrates, reduction of process temperatures to <400oC is an important requirement. Plasma treatment can be used to modify thin-film properties and device characteristics by modulating carrier concentration and density of oxygen vacancies [3]. Argon plasma treatment can improve reliability, as carbon concentration on the surface can be reduced, and oxidation enhancement on the surface can be achieved. This research aims to study the effect of plasma treatment on the stability of fully solution processed amorphous Indium Zinc Oxide (a-IZO) thin-film transistor (TFT).Our fully solution processed a-IZO TFTs were fabricated with a self-aligned top gate structure at a maximum fabrication temperature of 300oC. Initially, IZO precursor was spin-coated on Si/SiO2 substrate. Then, fluorinated-polysilsesquioxane (F-PSQ) was deposited with a thickness of ~200 nm which act as a gate-insulator, followed by an IZO layer to be transformed as conducting electrode after treatment. Self-aligned patterning, gate etching, and gate insulator etching were then performed. Lastly, Argon plasma treatment is performed via inductively coupled plasma (ICP), using reactive ion etching SAMCO 10-ip equipment for 5 seconds at room temperature with an ICP power, bias power, and working pressure of 300 W, 100 W, and 5 Pa, respectively. The Argon flow rate was also varied at 100, 75, and 50 sccm. The IZO TFT without plasma treatment was denoted as-fabricated sample. After plasma treatment, exposed IZO layers transform as source/drain and gate. TFT structure before and after plasma treatment can be seen in Fig. 1.Film surface morphology was studied using atomic force microscopy. As Argon concentration increased, the exposed IZO surface became rougher. We also checked the transfer characteristics, performed cyclic measurement, and bias stress tests. Transfer characteristics of TFTs with 90µm width and 10µm length were examined at several drain voltages (Vd = 0.1 V, 5.0 V, and 9.9 V) by a semiconductor parameter analyzer. Transfer curves for as-fabricated and after Ar-75 plasma treatment are shown in Fig 1. As-fabricated sample shows poor switching characteristics because of inactivated source/drain and gate electrodes. After plasma treatment, TFTs show superb characteristics which possibly happened because of changes in the metal-oxide bond formation which increased the conductivity in exposed area. The mobility significantly increased to 31.12 cm2/Vs, with a Vth= -0.3 V and subthreshold swing of 0.28 V/dec for Ar-75 sccm. TFT yield was evaluated by measuring 8 TFTs for each sample. Average mobility for Ar-50, Ar-75, and Ar-100 is 20.30 cm2/Vs, 22.93 cm2/Vs, and 19.88 cm2/Vs, respectively. The mobility increase corresponded to the thin-film quality improvement caused by change in VO and surface roughness [4]. However, excessive Argon gas flow also tend to make samples more conductive.To investigate device stability, positive bias stress (PBS, stress V g= 10 V) and negative bias stress (NBS, stress V g= -10 V) was performed for 2,000s. Lower on-current for all samples were observed as bias stress duration increased. A threshold voltage shift (∆Vth) for Ar-50, Ar-75, and Ar-100 of 0.2 V, -0.3 V, and 0.6 V, respectively after PBS, and 1.4 V, 2.9 V, and 0.7 V, respectively after NBS was observed. We expect that improvement via plasma treatment is due to two main factors. First, ion bombardment caused surface improvement and activated the electrode. Second, the chemical reaction induced by plasma treatment changed the metal-oxide bonds formation [5-6]. Thus, fully solution-processed a-IZO TFT with high mobility up to 31.12 cm2/Vs was achieved by Ar-75 plasma treatment, which also led to better stability under bias stress. These results show that performance enhancement of fully-solution processed a-IZO TFT by plasma treatment has a large potential for future low-temperature flexible device applications.Acknowledgment:This research was supported by JSPS Kakenhi Grant no. 22K14291. The authors thank Nissan Chemical Corporation for providing the IZO precursor solution.

Performance enhancement of solution-processed InZnO thin-film transistors by Al doping and surface passivation

Solution-processed oxide semiconductors have been considered as a potential alternative to vacuum-based ones in printable electronics. However, despite spin-coated InZnO (IZO) thin-film transistors (TFTs) have shown a relatively high mobility, the lack of carrier suppressor and the high sensitivity to oxygen and water molecules in ambient air make them potentially suffer issues of poor stability. In this work, Al is used as the third cation doping element to study the effects on the electrical, optoelectronic, and physical properties of IZO TFTs. A hydrophobic self-assembled monolayer called octadecyltrimethoxysilane is introduced as the surface passivation layer, aiming to reduce the effects from air and understand the importance of top surface conditions in solution-processed, ultra-thin oxide TFTs. Owing to the reduced trap states within the film and at the top surface enabled by the doping and passivation, the optimized TFTs show an increased current on/off ratio, a reduced drain current hysteresis, and a significantly enhanced bias stress stability, compared with the untreated ones. By combining with high-capacitance AlO x , TFTs with a low operating voltage of 1.5 V, a current on/off ratio of > 10 4 and a mobility of 4.6 cm2/(V·s) are demonstrated, suggesting the promising features for future low-cost, low-power electronics.

Effect of Hydrogen on Long-Term Reliability of InZnO TFTs Characterized by Low-Frequency Noise

The long-term reliability of InZnO (IZO) thin film transistors (TFTs) under a hydrogen-containing environment is researched. Hydrogen incorporation induces hydroxyl groups and oxygen vacancies, leading to the generation of electrons and extra random trap/emission processes in the IZO films. Consequently, the electrical properties and low frequency noise characteristics of IZO TFTs are deteriorated under the long-term hydrogen treatment. Additionally, the recovery characteristics of IZO TFTs after the hydrogen treatment demonstrate that the hydrogen induced hydroxyl groups and oxygen vacancies remain stable at room temperature. The oxygen vacancies can be eliminated, while the hydroxyl groups may still exist at a high temperature. These results may provide useful guidelines in the design and application of IZO TFTs.

Improvement in Electrical Characteristics of Eco-friendly Indium Zinc Oxide Thin-Film Transistors by Photocatalytic Reaction.

Eco-friendly solution-processed oxide thin-film transistors (TFTs) were fabricated through photocatalytic reaction of titanium dioxide (PRT). The titanium dioxide (TiO2) surface reacts with H2O under ultraviolet (UV) light irradiation and generates hydroxyl radicals (OH•). These hydroxyl radicals accelerate the decomposition of large organic compounds such as 2-methoxyethanol (2ME; one of the representative solvents for solution-processed metal oxides), creating smaller organic molecular structures compared with 2ME. The decomposed small organic materials have low molar masses and low boiling points, which help improving electrical properties via diminishing defect sites in oxide channel layers and fabricating low-temperature solution-processed oxide TFTs. As a result, the field-effect mobility improved from 4.29 to 10.24 cm2/V·s for IGZO TFTs and from 2.78 to 7.82 cm2/V·s for IZO TFTs, and the Vth shift caused by positive bias stress and negative bias illumination stress over 1000 s under 5700 lux decreased from 6.2 to 2.9 V and from 15.3 to 2.8 V, respectively. In theory, TiO2 has a permanent photocatalytic reaction; as such, hydroxyl radicals are generated continuously under UV irradiation, improving the electrical characteristics of solution-processed IZO TFTs even after four iterations of TiO2 recycling in this study. Thus, the PRT method provides an eco-friendly approach for high-performance solution-processed oxide TFTs.

Effect of Al2O3 Passivation Layer and Cu Electrodes on High Mobility of Amorphous IZO TFT

In this paper, we present a high mobility amorphous indium-zinc-oxide (a-IZO) thin film transistor (TFT) based on copper (Cu) source/drain electrodes (S/D) and aluminum oxide (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) passivation layer (PVL). The mechanism of high mobility for the a-IZO TFT based on Cu S/D with Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> PVL was proposed and experimentally demonstrated. The sputtering of Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> PVL induced a highly conductive channel layer due to the formation of In-rich layer on the back channel. Also, Cu S/D presented Schottky contact behavior compared with Mo S/D which behaved like Ohmic contact. Because the Schottky contact can block leakage current and the highly conductive channel achieved high on-current, the a-IZO TFT based on Cu S/D and Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> PVL performed remarkable saturation mobility up to 412.7 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs. This paper presents a feasible way to implement high mobility TFT arrays with Cu electrodes.

Low-temperature sol–gel oxide TFT with a fluoropolymer dielectric to enhance the effective mobility at low operation voltage

In this article, we propose a solution-processed high-performance amorphous indium–zinc oxide (a-IZO) thin-film transistor (TFT) gated with a fluoropolymer dielectric. Compared with a conventional IZO TFT with a silicon nitride dielectric, a fluoropolymer dielectric effectively reduces the operation voltage to less than 3 V and greatly increases the effective mobility 40-fold. We suggest that the dipole layer formed at the dielectric surface facilitates electron accumulation and induces the electric double-layer effect. The dipole-induced hysteresis effect is also investigated.

A High-Reliability Gate Driver Integrated in Flexible AMOLED Display by IZO TFTs

This paper presents a new gate driver integrated by IZO thin-film transistors (TFTs) with the etch stop layer structure on the polyimide substrate, which consists of nine TFTs and two capacitors. There are several advantages for the proposed gate driver, such as simple circuitry, full-swing output, low power, and good reliability. The proposed gate driver has been successfully integrated in a flexible active matrix organic light emitting display with the resolution of 200 (RGB) $\times 600$ , in which the conventional 2T1C pixel circuit with bottom-emission structure is used. It is shown that there are no distortion and good noise-suppressed characteristics for the output signals even up to 600 stages. In addition, the proposed gate driver has a good stability, since no voltage fluctuation occurs under 720-h test. Moreover, the flexible panel works well after a 10000 times repetitive bending performed on a test bench, which is mainly composed of a programmed logic controller and dc motor. During the bending test, the minimum curvature radius of flexible panel can reach to be about 5 mm.

Thin-Film Transistors With Neodymium-Incorporated Indium–Zinc-Oxide Semiconductors

A thin-film transistor (TFT) with a neodymium-doped indium–zinc-oxide (NIZO) channel layer was fabricated. It was found that the Nd element uniformly distributed in the whole NIZO films, which revealed a nanocrystalline structure, implying that Nd was incorporated into the IZO lattice rather than segregated as clusters. The NIZO TFT annealed at 300 °C showed a saturation mobility of 22.7 cm $^{2}\text{V}^{-1}\text{s}^{-1}$ , a turn-ON voltage of −1.32 V, a subthreshold swing (SS) of 0.23 V/decade, and small turn-ON voltage shift under negative gate bias stress (−0.42 V) and positive gate bias stress (0.40 V). As the annealing temperature increased, the threshold voltage of the NIZO TFTs became more and more negative. Compared with IZO TFTs without Nd, NIZO TFTs exhibited lower SS and less turn-ON voltage shift as the annealing temperature increased. It was found that the free carriers of NIZO can be lowered even with a small amount of Nd ( $\sim 1$ %). When annealed at a temperature of as high as 400 °C, the oxygen out-diffusion effect of NIZO was not as serious as that of IZO. Detailed studies showed that Nd atom could suppress the formation of oxygen vacancies due to the strong bonding strength of Nd–O (703 kJ/mol).

Gettering Effect Induced by Oxygen-Deficient Titanium Oxide in InZnO and InGaZnO Channel Systems for Low-Power Display Applications

This paper reported the IGZO and IZO thin-film transistor (TFT) with titanium-oxide semiconductor as channel capping layer. After the ${\hbox{TiO}}_{x}$ Gettering process, the oxygen vacancies in IGZO channel were successfully modified to maximize the carrier concentration and device mobility. The superior transfer characteristics included a low sub-threshold swing of 79 mV/decade, a very high mobility of ${\hbox{68}}~{\hbox{cm}}^{2}/{\hbox{V}}{\cdot}{\hbox{s}}$ , and good on/off-current ratio of ${\hbox{5.61}}\times {\hbox{10}}^{6}$ . However, the IZO channel with nano-crystallized grains and without Ga atom doping showed unfavorable transistor characteristics. In addition to apparently degraded transfer properties, the spontaneously oxidized ${\hbox{TiO}}_{x}$ capping layer also lead to an increase of channel parasitic resistance that limits the output driving current. Therefore, we believe that the existence of Ga–O bonds among IGZO channel would be helpful to stabilize oxygen diffusion behavior and electric structure during Gettering process.

Plasma-Enhanced Atomic Layer Deposition Processed SiO&lt;sub&gt;2&lt;/sub&gt; Gate Insulating Layer for High Mobility Top-Gate Structured Oxide Thin-Film Transistors

SiO2 processed by plasma-enhanced atomic layer deposition (PEALD) was applied as a gate insulator (GI) to the top gate high mobility InZnO (IZO) thin-film transistor (TFT). In as-fabricated devices, while IZO TFTs with GI processed by PEALD shows high ON/OFF ratio characteristics, the devices with GI deposited by plasma-enhanced chemical vapor deposition showed the conductive characteristics. From the secondary ion mass spectroscopy analysis, it is inferred that PEALD processed SiO2 generates fewer free electron donating elements in the active layer. The IZO TFT with PEALD processed GI exhibits a high-field effect mobility of 32.9 cm2/ $\text{V}\,\cdot \,\text{s}$ , $V_{\mathrm{\scriptscriptstyle ON}}$ of −0.3 V, and $\Delta ~V_{\mathrm{\scriptscriptstyle ON}}$ of 0.56 V under positive bias temperature stress (1 MV/cm, 60 °C, 3600 s) after being subject to thermal annealing at 350 °C.

Dual in-plane-gate coupled IZO thin film transistor based on capacitive coupling effect in KH550-GO solid electrolyte

Low-voltage electric-double-layer oxide-based thin-film transistors are of great prospect and investigative value in the fields of micro multi-state memory devices, detectors, electrochemical sensors, and biological synapses simulation, and so on. In addition, low-voltage electric-double-layer oxide-based thin-film transistors have increasingly attracted attention among researchers due to the characteristics of high mobility, high visible light transmittance and low temperature preparation. Currently, the researches about low-voltage electric-double-layer oxide-based thin-film transistors are broadly divided into two aspects. On the one hand, the researches focus on ZnO as a channel layer, source and drain electrode materials, then gradually develop into In, Sn and Ga oxides as well as complex oxides containing these elements, which has made tremendous progress. On the other hand, the development and research of the gate dielectric materials have received more attention. It is found that by adopting an organic/inorganic proton conductor film as the gate dielectric of low-voltage electric-double-layer oxide-based thin-film transistors, the protons in the gate dielectric will move in the direction away from gate, and finally accumulate on the surface of gate dielectric layer close to the channel layer, with the positive bias applied to the gate. In conclusion, though the researches about low-voltage electricdouble- layer oxide-based thin-film transistors have already made great progress, further explorations and investigations are necessary from its wide applications. Consequently, the development of new material architecture of low-voltage electric-double-layer oxide-based thin-film transistor is one way to achieve this goal. Silane coupling agents (3-triethoxysilylpropyla-mine)-graphene oxide (KH550-GO) solid electrolyte is prepared on plastic substrate by spin coating process. The electrical performances of dual in-plane-gate coupled protonic/electronic hybrid IZO thin film transistor gated by KH550-GO solid electrolyte are further studied. The results indicate that the electric-double-layer capacitance and proton conductivity of KH550-GO solid electrolyte respectively achieve 2.03 F/cm2 and 6.9910-3 S/cm, respectively. Due to high electric-double-layer capacitance and proton conductivity, protonic/electronic hybrid IZO thin film transistor gated by KH550-GO solid electrolyte has lower power consumption (its operation voltage ~2 V). Current on/off ratio of 1.23107 and field-effect mobility of 24.72 cm2/(Vs) are shown in the device. Due to the capacitive coupling effect of KH550-GO solid electrolyte, the device with the stimulus of dual in-plane-gate voltage, can effectively modulate the threshold voltage, the subthreshold swing and the field-effect mobility, and demonstrate AND logic operation successfully. Dual in-plane-gate coupled protonic/electronic hybrid IZO thin film transistors prepared in this paper have potential applications in the field of biosensors and artificial synapses.

Chemically robust solution-processed indium zinc oxide thin film transistors fabricated by back channel wet-etched Mo electrodes

We designed a systematic strategy for a chemically robust solution-processed IZO thin film transistor with back channel wet-etched Mo electrodes, which showed superior electrical performance and uniformity.

Electrohydrodynamic Jet Printed Indium–Zinc–Oxide Thin-Film Transistors

Electrohydrodynamic (EHD) jet-printed indium-zinc-oxide thin-film transistors (TFTs) were prepared at various annealing temperatures. The EHD jet was achieved by optimizing the process parameters; such as the precursor viscosity, driving voltages, and substrate temperatures. The EHD jet-printed IZO films were characterized using a range of analytical methods. Metal oxide formation was confirmed by X-ray photoelectron spectroscopy. The EHD jet-printed IZO TFTs showed good electrical properties: a mobility of 4.8 cm $^{2}/{\hbox{V}}\cdot{\hbox{s}}$ , a threshold voltage of 8.4 V, an on-to-off current ratio of ${\hbox{10}}^{7}$ , and a subthreshold slope of 1.2 V/dec at 400 $^{\circ}$ C. The positive and negative bias stability were also analyzed.

Improvement of electrical characteristics of solution-processed InZnO thin-film transistor by vacuum annealing and nitrogen pressure treatment at 200 °C

Electrical characteristics of the InZnO (IZO) thin-film transistor (TFT) using solution process were improved via vacuum annealing and N2 pressure treatment (PT) at 200 °C. Especially, the PT reduced the IZO film thickness and enhanced the IZO film density. It reduced the trap sites at the interface of IZO/gate insulator and those in the IZO bulk. Therefore, the PT IZO TFT exhibited a higher mobility of 4.44 cm2 V−1 s−1 and a steeper subthreshold swing of 0.79 V/decade than non-PT IZO TFT. The improvement of hysteresis on the PT IZO TFT was also observed.

Improvement in the Electrical Performance of Ge-Doped InZnO Thin-Film Transistor.

We fabricated amorphous oxide semiconductor thin-film transistors (TFTs) using Ge-doped InZnO (Ge-IZO) thin films as active-channel layers. The Ge-IZO thin films were deposited at room temperature by radio-frequency (RF) magnetron co-sputtering system, and then annealed in air for 1 h at 300 °C. Some processing parameters such as sputtering oxygen partial pressure [O2/(Ar + O2)] and sputtering power for GeO2 target were changed to investigate what was the optimal amount of Ge in the Ge-IZO active layer. A small concentration of Ge added to IZO by co-sputtering enhanced the carrier concentration, mobility, and conductivity; but further increase in Ge concentration degraded the device performance. In order to optimize the electrical properties of Ge-IZO TFTs, we tried to adjust the processing parameters and the best Ge-IZO TFT was obtained at a co-sputtering oxygen partial pressure of 2% and GeO2 target power of 10 W. The fabricated Ge-IZO TFT exhibited an on/off ratio of 3.0 x 10(7), a saturation mobility of 13.05 cm2/V·s, a subthreshold swing of 0.95 V/dec, and a threshold voltage of 0 V. XPS and XRD analyses of Ge-IZO films were performed to investigate the binding energies of atoms in Ge-IZO films and the crystallinity of the films. 90% transmittance of visible light was achieved, which makes the technology useful for transparent devices.

Six‐Fold Mobility Improvement of Indium‐Zinc Oxide Thin‐Film Transistors Using a Simple Water Treatment

DOI: 10.1002/aelm.201500014 Figure 1 a shows the process-fl ow for the fabrication of IZO TFTs. The TFTs with IZO fi lms that were immersed in DIW prior to fi nal crystallization at 250 °C are henceforth referred to as DIW-treated IZO TFTs and the TFTs with IZO fi lms that were not immersed in DIW are henceforth referred to as untreated IZO TFTs. Figure 1 b shows the schematic of the device structure and Figure 1 c shows the top-view image of an actual device obtained by a 3D optical surface profi ler (NewView 7300, Zygo). The output characteristics of the untreated and DIW-treated IZO TFTs are shown in Figure 1 d,e, respectively. Transfer characteristics of the untreated and DIW-treated IZO TFTs are shown in Figure 1 f. All TFTs work in a low operating voltage range due to the spin coated AlO x dielectric having high capacitance of ca. 151 nF cm −2 measured at 1 Hz (Figure S1, Supporting Information). Untreated IZO TFTs exhibited an average μ FE of ~8.6 ± 0.9 cm 2 V −1 s −1 with a drain on-current to off-current ratio ( I on / I off ) in the range of 10 4 –10 5 . Interestingly, DIW-treated IZO TFTs exhibited higher I on / I off (>10 6 ) with a maximum peak μ FE of ca. 51 ± 5 cm 2 V −1 s −1 , which is six times higher than the untreated IZO TFTs. The dual sweep of the transfer curve showed a very negligible hysteresis with a voltage difference of ca. 0.02 V between the forward and backward sweep (Figure S2, Supporting Information). No signifi cant difference in μ FE of the TFTs was observed with varying channel width to length ratio (W/L) from 5 to 10 (W = 500 μm, L = 100, 75, and 50 μm). The average sub-threshold swing ( SS ) value of untreated and DIW-treated IZO TFTs was found to be 0.189 ± 0.016 V dec −1 and 0.102 ± 0.012 V dec −1 , respectively. Reproducibility of the IZO TFTs with similar performance was checked with repeated experiments. The statistics of the TFT parameters obtained from different experiments is listed in Table S1, Supporting Information, and the corresponding transfer curves are shown in Figure S3, Supporting Information. These results represent the highest fi eld-effect mobility among the solution-processed TFTs using patterned metal oxide channel layers. Positive gate-bias stress (PBS) and negative gate-bias stress (NBS) stability tests were carried out, especially for the DIWtreated IZO TFT and the PBS results are shown in the left panel of Figure 1 g. A bias voltage of +/−1 V was applied to the gate terminal of the TFT during PBS/NBS while the drain and source voltage was fi xed as 0 V. Parallel shifting of the transfer curves was observed in the positive direction with increasing PBS duration. A maximum threshold voltage shift of +0.3 V was observed after 100 s of stress and no signifi cant threshold voltage shift was observed with further increase in PBS duration up to 3000 s. Similar shifting of the transfer curve in the negative direction was observed with increasing NBS duration up to 500 s (Figure S4a, Supporting Information). Parallel shifting of the transfer curves under PBS/NBS with no signifi cant change Transparent metal oxide based thin fi lm transistors (TFTs) have been extensively studied during the last decade due to their potential application in displays and other electronic devices. [ 1 ]

Effects of Hf incorporation on indium zinc oxide thin-film transistors using solution process

Thin-film transistors (TFTs) were fabricated by employing amorphous hafnium indium zinc oxide (HIZO) thin films as the active channel layer by the solution process. Thermogravimetry-differential thermal analysis, transmittance measurements, atomic force microscopy, scanning electron microscopy, x-ray diffraction, and Fourier transform infrared analysis were used to study the formation, structure, and optical properties of the HIZO films. The results showed that the addition of Hf to the IZO system resulted in suppression of carrier generation. The HIZO TFTs exhibited lower off-currents and higher onoff current ratios than IZO TFTs without Hf doping. HIZO TFTs with a Hf doping content of 5 at. % obtained a threshold voltage of 3.7 V, a mobility of 0.27 cm2 V-1 s-1, a subthreshold swing of 1.2 V/dec, and an on-off current ratio of 106.