In2O3 Thin-film Transistors Research Articles

O2 and H2O Barrier-Based High Reliability and Stability Using Polytetrafluoroethylene Passivation Layer for Solution Processed Indium Oxide Thin Film Transistors

The excellent chemical stability and hydrophobicity of Polytetrafluoroethylene (PTFE) polymer lead to its applicability in high-performance flexible electronic appliances. Though the detailed investigation for PTFE passivated metal oxide thin-film transistors (TFTs) is still lacking. Here, we report the highly stable oxygen barrier based on the PTFE passivation layer (PVL) spin-coated upon the lowtemperature solution-processed indium oxide (In₂O₃) TFTs. Particularly, by using the solution-process method, fabrication cost and multiple time-consuming steps are eliminated in the counterpart of the radio frequency magnetron sputtering. The PTFE PVL can significantly suppress the adsorption of surrounding moisture and oxygen from environments owing to its most chemically robust carbon-fluorine bond. In addition, the comprehensive electrical performance in terms of the saturation mobility, on-off current ratio, threshold voltage, subthreshold swing, and interface trap density of the In₂O₃ TFTs passivated with different weight ratios of PTFE are compared. The results show that 1 wt.% PTFE passivated In2O3 TFT demonstrates a drastically reduced threshold voltage and highest stability under constant bias. Consequently, oxygen barrier-based PTFE is a promising PVL material for various emerging electronic devices.

Enhanced Electrical Performance and Stability of La‐Doped Indium Oxide‐Based Thin‐Film Transistors and Application Explorations

Metal‐oxide‐based thin‐film transistors (TFTs) fabricated by aqueous solution method are attracting more attention due to their potential applications in large‐scale display devices. Herein, solution‐processed TFTs with InLaO as channel layer are prepared as a function of lanthanum (La) doping molar ratio (La/In). Compared with In2O3 TFT, InLaO‐0.5 TFT demonstrates improved electrical performance, including a large μFE of 21.35 cm2 V−1s−1, a higher Ion/Ioff of ≈108, a smaller interfacial trap states (Dit) of 5.01 × 1011 cm−2, and a smaller subthreshold slope of 0.076 V decade−1. Low‐frequency noise tests are also carried out and conclude that the interfacial trap density of In2O3 TFTs can be modulated by La doping. Meanwhile, InLaO‐0.5 TFT also represents excellent bias stress stability, including threshold voltage shift (ΔVTH) of 0.13 and −0.03 V under positive and negative bias stress for 3600 s, respectively. Finally, a low‐voltage resistor‐loaded inverter has been built based on InLaO‐0.5 TFT, exhibiting full‐swing characteristics and a maximum gain of 10.2. All experimental results demonstrate the potential application of aqueous solution technology for future low‐cost, energy‐efficient, large‐scale, and high‐performance electronics.

Effects of atmosphere composition during direct ultraviolet-light patterning of solution-deposited In2O3 thin film transistors

Sol-gel synthesis is widely used to fabricate metal oxide thin films by solution, but it requires high-temperature thermal annealing to fully convert precursors to metal oxides. Exposure to Ultraviolet (UV) light before thermal annealing of precursor films has been shown to reduce the conversion temperature, with the added benefits of film patterning when done through a shadow mask and improved device performance. However, the mechanism by which UV exposure under different atmospheric compositions affects the properties of metal oxide films after thermal annealing has not been investigated. Here, we control the atmospheric composition during UV-patterning—prior to high-temperature thermal annealing—of In2O3 sol-gel films which serve as the semiconductor in thin-film transistors. Despite all films being annealed at 250°C in air after UV patterning, films exposed to UV under oxygen-containing atmospheres have higher metal-oxygen-metal bonding and exhibit higher transistor mobility compared to the films exposed to UV under N2 atmosphere. The origin of the effect of atmospheric composition on mobility is studied through X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy and is revealed to be the result of the reformation of the nitrate species in the films under more oxidizing atmospheres during UV exposure. These nitrates can be completely removed by thermal annealing, facilitating more complete metal-oxygen-metal bond formation, which is reflected in higher OI XPS signal and transistor mobility. In contrast, films processed under N2 atmosphere during UV exposure contain nitrite species that cannot be removed by thermal annealing, resulting in less metal-oxygen-metal bond formation and lower mobility.

Ecofriendly Solution-Combustion-Processed Thin-Film Transistors for Synaptic Emulation and Neuromorphic Computing.

The ecofriendly combustion synthesis (ECS) and self-combustion synthesis (ESCS) have been successfully utilized to deposit high-k aluminum oxide (AlOx) dielectrics at low temperatures and applied for aqueous In2O3 thin-film transistors (TFTs) accordingly. The ECS and ESCS processes facilitate the formation of high-quality dielectrics at lower temperatures compared to conventional methods based on an ethanol precursor, as confirmed by thermal analysis and chemical composition characterization. The aqueous In2O3 TFTs based on ECS and ESCS-AlOx show enhanced electrical characteristics and counterclockwise transfer-curve hysteresis. The memory-like counterclockwise behavior in the transfer curve modulated by the gate bias voltage is comparable to the signal modulation by the neurotransmitters. ECS and ESCS transistors are employed to perform synaptic emulation; various short-term and long-term memory functions are emulated with low operating voltages and high excitatory postsynaptic current levels. High stability and reproducibility are achieved within 240 pulses of long-term synaptic potentiation and depression. The synaptic emulation functions achieved in this work match the demand for artificial neural networks (ANN), and a multilayer perceptron (MLP) is developed using an ECS-AlOx synaptic transistor for image recognition. A superior recognition rate of over 90% is achieved based on ECS-AlOx synaptic transistors, which facilitates the implementation of the metal-oxide synaptic transistor for future neuromorphic computing via an ecofriendly route.

Investigation of the Determining Factors for the “Mobility Boost” in High‐k‐Gated Transparent Oxide Semiconductor Thin‐Film Transistors

AbstractIn metal‐oxide thin‐film transistors (TFTs), high‐k gate dielectrics often yield a higher electron mobility than SiO2. However, investigations regarding the mechanism of this high‐k “mobility boost” are relatively scarce. To explore this phenomenon, solution‐processed In2O3 TFTs are fabricated using eight different gate dielectrics (SiO2, Al2O3, ZrO2, HfO2, and bilayer SiO2/high‐k structures). With these structures, the total gate capacitance can be varied independently from the semiconductor–dielectric interface to study this mobility enhancement. It is shown that the mobility enhancement is a combination of the effects of areal gate capacitance and interface quality for disordered oxide semiconductor devices. The ZrO2‐gated TFTs achieve the highest mobility by inducing more accumulation charge with higher gate capacitance. Surprisingly, however, when the gate capacitance is held constant, no mobility enhancement is observed with the high‐k gate dielectrics compared to SiO2.

Tuning the electrical performance of solution-processed In2O3TFTs by low-temperature with HfO2-PVP hybrid dielectric

Here in, we investigated the solution-processed and hysteresis-free indium oxide (In2O3) thin-film transistors (TFTs) fabricated with hafnium oxide-poly(vinyl)phenol (HfO2-PVP) hybrid thin film as gate dielectric by a low temperature sol-gel method. The hybrid dielectric thin film exhibits unique dielectric properties of a low leakage current density of 1.2 × 10−8 A/cm2, gate areal capacitance of 44.4 nF/cm2 and a dielectric constant (k) of 6.5 at 1 kHz. In addition, the hybrid films show a high-quality homogeneous and pin-hole free surface with a low surface roughness (Rq) of 0.75-nm and display a low surface energy of 36.7 mJ/m2 with hydrophobic behavior. This dielectric material is then used used in In2O3 TFTs as the gate insulator. Here, the In2O3 semiconductor as the channel layer is examined at 200 °C and 230 °C temperatures for TFT characteristics. The final TFT device fabricated at 230 °C showed much improved electrical performance with the mobility (μsat) of 2.6 cm2/V.s, Ion/Ioff ratio of 105, subthreshold swing (SS) of 330 mV/dec, threshold voltage (VT) of 0.1 V at a low operating voltages because of a better interface between dielectric and semiconductor with fewer charge carriers traps. This study could be an effective approach for the next generation of all-solution fabrication of TFTs that could play a vital role in optoelectronics applications.

The effect of post-metal annealing on the electrical performance and stability of two-step-annealed solution-processed In2O3 thin film transistors

In this work, solution-processed indium oxide (In2O3) thin film transistors (TFTs) were fabricated by a two-step annealing method. The influence of post-metal annealing (PMA) temperatures on the electrical performance and stability is studied. With the increase of PMA temperatures, the on-state current and off-state current (Ion/Ioff) ratio is improved and the sub-threshold swing (SS) decreased. Moreover, the stability of In2O3 TFTs is also improved. In all, In2O3 TFT with post-metal annealing temperature of 350°С exhibits the best performance (a threshold voltage of 4.75 V, a mobility of 13.8 cm2/V, an Ion/Ioff ratio of 1.8 × 106, and a SS of 0.76 V/decade). Meanwhile, the stability under temperature stress (TBS) and positive bias stress (PBS) also show a good improvement. It shows that the PMA treatment can effectively suppress the interface trap and bulk trap and result in an obviously improvement of the In2O3 TFTs performance.

Improved High-Performance Solution Processed In₂O₃ Thin Film Transistor Fabricated by Femtosecond Laser Pre-Annealing Process

The low-temperature annealing process has a critical impact on the electrical performance of thin-film transistors (TFTs). This paper reports significant performance enhancements of TFTs using a femtosecond laser pre-annealing (FLA)-based preparation method. The solution-processed In <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> films were fabricated by FLA at various laser irradiation times and then annealed on a hot-plate at 230 °C. When the FLA time was set to 30 s, the device exhibited high saturation mobility of 10.03 ± 0.64 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs, I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> of 3.4×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> , low V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> of 0.14 ± 0.64 V, and small SS of 1.44 ± 0.37 V/dec. The FLA process improved the formation of M-O lattices effectively, which led to an improvement in mobility. Furthermore, the gate-bias-stress stability and time-dependent environmental stability were improved considerably by the FLA process. These results show that high-performance In <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> TFTs can be prepared at low temperatures using FLA-centered annealing technology. This work suggests that the FLA preparation method has tremendous potential for the fabrication of low-cost, high performance, and flexible TFT devices.

Bias stability of solution-processed In2O3 thin film transistors

We report the effect of bias stress on the drain current and threshold voltage of n-channel thin-film transistors based on solution processed In2O3 layers. Application of a positive gate bias for variable time-periods led to displacements of the transfer curves in the positive gate bias direction. On switching off the gate bias, the transfer curves returned close to their pre-stress state on a timescale similar to that when the gate bias was switched on. The time dependence of the threshold voltage shift is described well by a stretched-exponential model. The temporal behaviour of the threshold voltage shifts is consistent with charge trapping as the dominant effect, although some defect formation cannot be ruled out.

Comproportionation Reaction Synthesis to Realize High‐Performance Water‐Induced Metal‐Oxide Thin‐Film Transistors

AbstractSolution‐processed metal‐oxide thin films have been widely studied in low‐power and flexible electronics. However, the high temperature required to form a condensed and uniform film limits their applications in flexible and low‐cost electronics. Here, a novel and environmental‐friendly comproportionation reaction synthesis (CRS) is presented to obtain amorphous aluminum oxide (AlOx) thin films for solution‐processed thin‐film transistors (TFTs) employing water as the precursor solvent. The thermal decomposition of CRS‐AlOx precursor is completed at ≈300 °C, which is 100 °C lower than that of the conventional water‐induced AlOx. The morphological, optical, compositional, and electrical properties of CRS‐AlOx dielectric films are studied systematically. Meanwhile, TFTs based on water‐induced In2O3 metal oxide semiconductor layers deposited on these dielectrics at low temperatures are formed and characterized. Compared with TFTs based on conventional AlOx showing low mobility and low clockwise hysteresis, In2O3 TFTs based on CRS‐AlOx exhibit improved electrical performance and counterclockwise hysteresis in the transfer curves. Water‐induced TFTs fabricated on CRS‐AlOx formed at a low temperature of 250 °C have average mobility of 98 cm2 V−1 s−1. Through chemical composition characterization and electrical characterization, the high mobilities of TFTs based on CRS‐AlOx dielectrics are correlated to trap states, which resulted in counterclockwise hysteresis in the transfer curves.

Gas adsorption effects on electrical properties of amorphous In2O3 thin-film transistors under various environments

We report the electrical properties of amorphous In2O3 thin-film transistors (TFTs) measured under various environments without annealing treatment. Although the as-deposited TFT showed superior semiconducting properties in air (μsat: 32.7 cm2 V−1 s−1, Ion/Ioff: 4.2 × 108, ss: 0.54 V/dec), its current–voltage (I–V) characteristics changed drastically after evacuation. The capacitance–voltage (C–V) characterization revealed that the transition of the TFT properties from semiconducting to metallic might be caused by the reduction of electron trap states. In addition, the observed peak C–V behavior suggested that large amounts of oxygen ion impurities are included in the film that may not diffuse out even after evacuation. The transition of the TFT properties is thus caused by O2 desorption due to the In2O3 on the surface rather than that inside the film. The large amounts of ion impurities present in the as-deposited In2O3 film need to be controlled for the realization of future room-temperature TFT fabrication technology.

Role of the electronically-active amorphous state in low-temperature processed In2O3 thin-film transistors.

Metal oxide (MO) thin-film transistors (TFTs) are expected to enable low-cost flexible and printed electronics, given their excellent charge transport, low processing temperatures and solution processability. However, achieving adequate mobility when processed scalably at low temperatures compatible with plastic electronics is a challenge. Here, we explore process-structure-transport relationships in blade-coated indium oxide (In2O3) TFTs via both sol-gel and combustion chemistries. We find that the sol-gel chemistry enables n-type TFTs when annealed at 200 °C to 225 °C with noticeable electron mobility ((3.4 ± 1.3) cm2V-1s-1) yet minimal In2O3 crystallinity and surprisingly low levels of the metal-oxygen-metal (M-O-M) lattice content (≈46 %). Increased annealing temperatures result in the appearance of nanocrystalline domains and an increase in M-O-M content to ≈70 %, without any further increase in mobility. An actetylacetone combustion-assisted ink lowers the external thermal budget required for In2O3 crystallization but bypasses the electronically-active amorphous state and underperforms the sol-gel ink at low temperatures. Grain boundary formation and nanocrystalline inclusions in these films due to rapid combustion-assisted crystallization are suggested to be the likely origin behind the significantly compromised charge transport at low-temperatures. Overall, this study emphasizes the need to understand the complex interplay between local order (nanocrystallinity) and connectivity (grain boundary, amorphous phases) when optimizing low-temperature processed MO thin films.

High-Performance Thin-Film Transistors with Aqueous Solution-Processed NiInO Channel Layer

We report the aqueous-solution-processed Ni-doped In2O3 (NixIn2–xO3, NiInO) thin-film transistors (TFTs) for the first time. The effect of Ni doping on In2O3 microstructure, oxygen defects, and the electron transport properties are investigated by extensive characterization techniques. Analyses indicate that the oxygen vacancies in NiInO are suppressed as the Ni-doping concentration increases, leading to a lower off-state current and a positive shift in threshold voltage. The optimized NiInO TFTs exhibit a high mobility of 17.71 cm2/(V s), on/off current ratio > 106, threshold voltage of 4.21 V, and superior bias stress stability. The success of Ni doping could be attributed to the small ion radius of Ni, large Lewis acid value, and strong Ni–O bond strength. Therefore, the fabricated NiInO TFT provides a bright path for the development of high-performance oxide TFTs.

Low-temperature fabrication of Sr–N co-doped In2O3 thin film by aqueous route and its application to high performance InSrNO thin film transistor

This work explores a strategy of Sr3+ and N3− co-doping in InSrNO thin film to simultaneously improve stability and electrical performance of In2O3 thin film transistors (TFT). The aqueous route is proposed for low-temperature (<300 °C) thin film fabrication and accurate control of dopant composition. The influences of Sr–N co-doping on the chemical and structure of the InSrNO thin films are investigated by x-ray diffraction and x-ray photo electron spectroscopy measurements. The stability of InSrNO TFTs under the bias/illumination stress has been tested. The optimized InSrNO TFT (Sr: 0.5 mol%, N: 10 mol%) exhibits both the superior electrical performance and stability (a µ of 16.38 cm2 V−1 s−1, VTH of 2.91 V, SS of 0.24 V dec−1, a ΔVTH of 1.54 V under the positive bias stress, and a ΔVTH of −1.02 V under the negative bias illumination stress). The results demonstrate that Sr–N co-doping can improve electrical performance and stability of In2O3 TFT, which is attributed to the decrease of oxygen-related defects.

Polymer-Assisted Deposition of Gallium Oxide for Thin-Film Transistor Applications.

We report the fabrication of gallium oxide (GaOx) thin films by a novel polymer-assisted deposition (PAD) method. The influence and mechanism of postannealing temperature (200-800 °C) on the formation and properties of GaOx thin films are investigated by complementary characterization analyses. The results indicate that solution-deposited GaOx experiences the elimination of organic residuals as well as the transformation of amorphous GaOx to crystalline GaOx with the increase in annealing temperature. High-quality GaOx could be achieved with a smooth surface, wide band gap, and decent dielectric performance. Moreover, the solution-processed In2O3 thin-film transistors based on optimized GaOx dielectrics demonstrate outstanding electrical performance, including a low operating voltage of 5 V, a mobility of 3.09 cm2 V-1 s-1, an on/off current ratio of 1.8 × 105, and a subthreshold swing of 0.18 V dec-1. Our study suggests that GaOx achieved by PAD shows great potential for further low-cost and high-performance optoelectronic applications.

0.6V Threshold Voltage Thin Film Transistors With Solution Processable Indium Oxide (In2O3) Channel and Anodized High-$\kappa$ Al2O3 Dielectric

Low-voltage operation and low processing temperature of metal oxide transistors remain a challenge. Commonly metal oxide transistors are fabricated at very high processing temperatures (above 500°C) and their operating voltage is quite high (30-50 V). Here, thin-film transistors (TFT) are reported based upon solution processable indium oxide (In <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> ) and room temperature processed anodized high-κ 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> ) for gate dielectrics. The In <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> TFTs operate well below the drain bias (Vds) of 3.0 V, with on/off ratio 105, subthreshold swing (SS) 160 mV/dec, hysteresis 0.19 V, and low threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) 0.6 V. The electron mobility (μ) is as high as 3.53 cm2/V.s in the saturation regime and normalized transconductance(gm) is 75 μS/mm. In addition, the detailed capacitance-voltage (C-V) analysis to determine interface trap states density was also investigated.The interface trap density (Dit) in the oxide/semiconductor interface was quite low, i.e., 0.99 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> -2.98 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> , signifying acceptable compatibility of In <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> with anodic 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> .

Defect Self‐Compensation for High‐Mobility Bilayer InGaZnO/In2O3 Thin‐Film Transistor

AbstractHere, the bilayer InGaZnO/In2O3 thin‐film transistors (TFTs) are deposited by radio‐frequency magnetron sputtering at room temperature. A high field‐effect mobility (μFE) of 64.4 cm2 V−1 s−1 and a small subthreshold swing (SS) of 204 mV per decade are achieved in the bilayer‐stack TFTs fabricated upon SiO2/Si substrate, with large improvement compared to the single‐layer InGaZnO and In2O3 TFTs. Implementing HfO2 and Si3N4 as high‐k gate dielectrics, μFE and SS are correspondingly enhanced to be 67.5 and 79.1 cm2 V−1 s−1, and 85 and 92 mV per decade in the bilayer TFTs. Defect self‐compensation effect is also revealed, i.e., (In)+ + (O)− → In − O, while, respectively, considering the indium‐ and oxygen‐related defects in InGaZnO and In2O3 and exploring the numerical simulations in SILVACO/Atlas (for electrical performance) and Quantum Espresso (for physical analysis). The InO formation can result in a significant reduction in defect density (validated by the X‐ray photoelectron spectra and low‐frequency noise characterizations) and therefore improvement of μFE and SS in the bilayer‐stack TFT. The important role of defect self‐compensation mechanism while combining different individual channel layers in the oxide semiconducting TFTs is underlined and highly potential application in next‐generation, fast‐speed flexible displays is shown.

Electrical Stability of Solution-Processed Indium Oxide Thin-Film Transistors.

We investigated the electrical stability of bottom-gate/top-contact-structured indium oxide (In₂O₃) thin-film transistors (TFTs) in atmospheric air and under vacuum. The solution-processed In₂O₃ film exhibits a nanocrystalline morphology with grain boundaries. The fabricated In₂O₃ TFTs operate in an n-type enhancement mode. Over repeated TFT operation under vacuum, the TFTs exhibit a slight increase in the field-effect mobility, possibly due to multiple instances of the "trapping and release" behavior of electrons at grain boundaries. On the other hand, a decrease in the fieldeffect mobility and an increase in the hysteresis are observed as the measurement continues in atmospheric air. These results suggest that the electrical stability of solution-processed In₂O₃ TFTs is significantly affected by the electron-trapping phenomenon at crystal grain boundaries in the In₂O₃ semiconductor and the electrostatic interactions between electrons and polar water molecules.

Eco-friendly, low-temperature solution production of oxide thin films for high-performance transistors via infrared irradiation of chloride precursors

In this paper, we present the infrared (IR) irradiation of chloride precursors as a promising method for the eco-friendly, low-temperature solution fabrication of oxide film devices, which typically require thermal annealing at temperature over 450 °C. By the IR irradiation of AlCl3 precursor, high-quality Al2O3 dielectric films were prepared at a low temperature of 230 °C. The obtained Al2O3 dielectric layers had high dielectric properties, such as a high capacitance of 158 nF/cm2 and a small leakage current of 5.4 × 10−8 A/cm2. Various structure characterizations confirmed the high quality of Al2O3 films produced by IR irradiation. Moreover, full low-temperature solution-produced thin-film transistors (TFTs) were fabricated through the IR irradiation of chloride precursors. The In2O3 TFTs achieved a high mobility of 33.6 cm2V−1s−1 at a small operation voltage of 4 V. Compared with the common thermal annealing method, IR irradiation results in better precursor conversion, higher oxygen lattice, and fewer oxygen defects. These results suggest that IR irradiation can serve as a new approach for the eco-friendly, low-temperature solution production of various oxide thin films and devices. The method is also very promising for the low-energy production of functional materials and devices.

Raman spectroscopy study of solution-processed In2O3 thin films: effect of annealing temperature on the characteristics of In2O3 semiconductors and thin-film transistors

We investigate the effect of annealing temperature on the characteristics of solution-processed indium oxide (In2O3) films. From thermogravimetric analysis of the precursor solution, annealing temperatures of 150, 350, and 450 °C are adopted. The In2O3 films are analyzed by ultraviolet/visible spectroscopy, atomic force microscopy, grazing incidence X-ray diffraction, and Hall-effect measurement. Raman spectroscopy is used to examine the crystal polymorphism of the solution-processed films. Experimental results suggest that the optimal annealing temperature can be 350 °C. The transistor with the In2O3 semiconductor annealed at 350 °C exhibits the field-effect mobility of 1.4 V/cm2 and on/off ratio of 2.1 × 106.