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An Au@ZnO/rGO nanocomposite demonstrates a sensitive, selective, and ultra-low detection limit for NO2 sensing (5 ppb-1 ppm) at 60 °C.

Grey Wolf Optimizer (GWO) has been proposed recently. As GWO has superior performance, it has been employed to solve various numerical and engineering issues. However, it easily traps into stagnation when solving complex and multimodal problems. GWO mainly searches around the top three wolves and assigns the same weights to them, deteriorating the convergence and exploration. A reinforced exploitation and exploration GWO (REEGWO) is developed. In the proposed REEGWO algorithm, the top three wolves are given different weights on the basis of their knowledge about the location of the prey. Then, a random search based on the tournament selection is used to enhance the exploration. A well-designed mechanism is developed to balance exploration and exploitation. The experimental results have proved that REEGWO is perfect among GWO and its four recently top variants. Then, the proposed REEGWO is compared with the latest heuristic algorithms and their latest variants. The results have shown that REEGWO is competitive. Four real-world applications are also solved by six algorithms, and results have further validated the efficiency of REEGWO.

Solution-grown indium oxide (In2O3) based thin-film transistors (TFTs) hold good prospects for emerging advanced electronics due to their excellent mobility, prominent transparency, and possibility of low-cost and scalable manufacturing; however, pristine In2O3 TFTs suffer from poor switching characteristics due to intrinsic oxygen-vacancy-related defects and require external doping. According to Shanmugam’s theory, among potential dopants, phosphorus (P) has a large dopant–oxygen bonding strength (EM-O) and high Lewis acid strength (L) that would suppress oxygen-vacancy related defects and mitigate dopant-induced carrier scattering; however, P-doped In2O3 (IPO) TFTs have not yet been demonstrated. Here, we report aqueous solution-grown crystalline IPO TFTs for the first time. It is suggested that the incorporation of P could effectively inhibit oxygen-vacancy-related defects while maintaining high mobility. This work experimentally demonstrates that dopant with high EM-O and L is promising for emerging oxide TFTs.

As one of the promising next-generation electronics, brain-inspired synaptic resistive random access memory (RRAM) devices with stacked solution-processed (SP) spin-coated resistive switching (RS) ...

Urea electrolysis provides a promising approach for simultaneous energy-saving hydrogen production and wastewater utilization; however, the total reaction rate is severely restricted by the sluggish kinetics of the anodic urea oxidization reaction (UOR). Herein, we report a universal and highly controllable electrochemical defect-engineering approach to enrich the active sites on transition metal oxides toward promoted UOR catalysis. A large number of oxygen vacancies (Vo) were introduced on the surface of a Co3O4 nanowire model-material through negative potential tuning, leading to significantly increased UOR activity of the material. At a potential of 1.34 V vs. RHE, the defect-engineered catalyst delivers an optimal UOR current density of 100 mA cm−2, which is much higher than that (42 mA cm−2) offered by the original Co3O4 catalyst, and outperforms the best reported noble-metal-free UOR catalysts. Experimental results further reveal that the formation of Vo can effectively reduce the charge transport/transfer resistances both inside the nanowires and at the catalyst/electrolyte interface, giving rise to improved UOR activity. These findings suggest the great potential of this electrochemical defect-engineering strategy in the design of defect-enriched catalysts for advanced electrocatalysis.

Amorphous gallium tin oxide (GTO) thin films were prepared by a facile, and eco-friendly, aqueous solution process and their applications in thin-film transistors (TFTs) were investigated. The success of the aqueous route was realized by introducing tin fluoride (SnF2) instead of the traditional tin chloride (SnCl2) solute. The roles of adding Ga on the GTO’s microstructural, optical, chemical, and electrical performance were comprehensively studied. It was found that Ga can frustrate the crystallization while it augments the optical bandgap (Eg) value of pristine SnO2. More importantly, using Ga could effectively inhibit the formation of oxygen vacancies, thus greatly improving the electrical performance of the GTO TFTs. The amorphous GTO TFTs with a Ga content of 45% exhibited optimum performance, with a saturation mobility (μsat) of 4.26 cm2/V s, an on/off current ratio (Ion/Ioff) >107, and a decent bias stress durability.

In this study, pulsed laser deposition method (PLD) was employed to grow MgxZn1-xO films on quartz substrates. The optimal deposition temperature of 300 °C for MgxZn1-xO film was decided and Mg0.38Zn0.62O, Mg0.56Zn0.44O and Mg0.69Zn0.31O films were grown respectively using MgxZn1-xO targets with different Mg contents (x = 0.3, 0.5 and 0.7). As-deposited Mg0.38Zn0.62O film possessed the mixed-phase (hexagonal and cubic phase) structure, appropriate band gap of 4.68 eV and smaller surface roughness of 1.72 nm, and the solar-blind photodetector (PD) based on it was fabricated. The key features of our PD are the cutoff wavelength of 265 nm lying in solar-blind band, lower dark current (Idark) of 88 pA, higher peak responsivity of 0.10 A/W and bigger Ilight/Idark ratio of 1688, which provide the new idea for the application of solar-blind PDs based on MgxZn1-xO films.

In this paper, we report aqueous solution-processed boron-doped gallium oxide dielectric thin films for high-performance oxide thin-film transistors. The role of B incorporation on the microstructu...

Recently, metal surface plasma technology has been widely used to improve the quantum efficiency of optoelectronic devices, such as ZnO light-emitting diodes (LEDs). In this work, Ag films with the appropriate thickness were prepared by evaporation and annealed, and a layer of ZnCdO films with different Cd concentrations was grown on the Ag films by the pulsed laser deposition method. During this process, the changes in the Cd concentrations caused the near-band edge (NBE) emission of the ZnCdO films to be continuously adjusted in the ultraviolet to green wavelength range by controlling the oxygen pressure. The prepared Ag nanoparticles and ZnCdO composite films were used to study the metal localized surface plasmon (LSP) effect. The results show that the enhanced or reduced photoluminescence intensity of ZnCdO NBE depends on the probability of electrons transport to either the LSP level or the Fermi level of the metal. This discovery provides an important theoretical basis for the preparation of ZnCdO semiconductor LEDs in the future.

Tungsten oxide microflowers (WO3 MFs) were fabricated by a simple hydrothermal process through adjusting the pH of the solution by HCl. These MFs possess the outer diameters of about 2 μm and are composed of numerous nanoplates with the average pore size of 10.9 nm. Chemiresistive activity of as-fabricated WO3 MFs sensor was attempted towards oxidizing and reducing target gases, revealing a superior selectivity to NO2 with a maximum response of 22.95 (2 ppm NO2) @105 °C compared to other target gases. One of the key features of as-fabricatedWO3 MFs sensor is the lower detection limit of 125 ppb and operating temperature of 105 °C to NO2 with better reproducibility, signifying commercial prospective of the developed sensor materials. Finally, the gas sensing mechanism of WO3 MFs sensor has been proposed.

A p-GaN/i-MgO/n-ZnO nanorod array (NRA) heterojunction light-emitting diode has been fabricated. Its room-temperature electroluminescence spectra under different forward biases revealed a strong emission band across the whole visible region, which was blue-shifted when increasing the forward bias. The origin of this visible emission is considered to be related to oxygen vacancy (VO) defects in different valence states, where the blue emission (∼ 460 nm) comes from neutral oxygen vacancy (VOX ) defects and the green emission (∼ 520 nm) from singly charged oxygen vacancy (VO+ ) defects, while the yellow (∼ 580 nm) and red emission (∼ 670 nm) are attributed to doubly charge oxygen vacancy (VO++ ) defects. These VO defects in different states can convert into one another under different excitation conditions, resulting in the blue-shift of the emission peak as the forward voltage is increased.

Thin-film transistors (TFTs) based on solution-derived metal oxides hold great potential in emerging low-cost large-area printed electronics. Despite recent impressive progress, these device performances are far behind those of their corresponding vacuum-based counterparts, impeding their future commercialization. In this work, we designed and created high-performance TFTs based on a nanometer-thick (down to 5 nm) crystalline In–Sm–O channel via aqueous solution processing, with a performance comparable to those of existing vacuum-processed metal oxides. The microstructural, chemical, optical, and electrical properties of the ultra-thin In–Sm–O samples as a function of Sm doping content (0–10%) were comprehensively investigated. The In–Sm–O TFTs (5% Sm) on SiO2/Si dielectrics demonstrated state-of-the-art performance, including a high mobility of 21.51 ± 1.33 cm2 V−1 s−1, subthreshold swing of 0.66 ± 0.06 V per decade, threshold voltage of 2.14 ± 0.44 V, on/off current ratio >108, and remarkable bias stress stability. The success of In–Sm–O was attributed to the high quality of the crystalline In2O3 matrix, the ideal nature of Sm dopant in suppressing oxygen vacancies, as well as the ultrathin and atomically smooth nature of the channel layer. Therefore, the aqueous solution-processed ultra-thin In–Sm–O channel is expected to enable the realization of future low-cost, large-area, and high-performance green electronics.

The effects of hydrogen peroxide (H2O2) on the device properties and stabilities of solution-processed AlOx metal-oxide-semiconductor capacitors (MOSCAPs) were investigated. It is demonstrate. d that H2O2 is a strong oxidizer to decompose precursor residuals, reduce oxygen vacancy (Vo) and defects density of solution-processed AlOx thin films. The interface quality and the bias-stress (BS) stability of AlOx MOSCAPs were improved by employing H2O2. Furthermore, through carrying out on-site measurements, 7.5 M H2O2 AlOx MOSCAPs exhibited ignorable radiation-induced oxide traps and interface traps under biased-radiation-stress (BRS) with a total dose up to 42 Gy (SiO2). The 7.5 M H2O2 AlOx MOSCAPs also demonstrate the ability to recover under radiation after the bias was interrupted. The reduced number of Vo and high AlOx concentration of 7.5 M H2O2 AlOx could suppress the radiation-induced trapping/de-trapping behavior among the AlOx bulk and the breaking of Si–H bonds at the AlOx/Si interface. Besides, through biased-illumination-stress (BIS) measurements, the breaking of Si–H bonds under negative biased-radiation-stress (NBRS) was further proved. The results demonstrate that employing H2O2 in the solution-process is simple and effective; it has significant potential to improve the stabilities of large-area electronics for nuclear and aerospace applications.

The highly parallel artificial neural systems based on transistor-like devices have recently attracted widespread attention due to their high-efficiency computing potential and the ability to mimic biological neurobehavior. For the past decades, plenty of breakthroughs related to synaptic transistors have been investigated and reported. In this work, a kind of photoelectronic transistor that successfully mimics the behaviors of biological synapses has been proposed and systematically analyzed. For the individual device, MXenes and the self-assembled titanium dioxide on the nanosheet surface serve as floating gate and tunneling layers, respectively. As the unit electronics of the neural network, the typical synaptic behaviors and the reliable memory stability of the synaptic transistors have been demonstrated through the voltage test. Furthermore, for the first time, the UV-responsive synaptic properties of the MXenes floating gated transistor and its applications, including conditional reflex and supervised learning, have been measured and realized. These photoelectric synapse characteristics illustrate the great potential of the device in bio-imitation vision applications. Finally, through the simulation based on an artificial neural network algorithm, the device successfully realizes the recognition application of handwritten digital images. Thus, this article provides a highly feasible solution for applying artificial synaptic devices to hardware neuromorphic networks.

Gallium oxide (Ga2O3) is widely used as an ultra-wide bandgap semiconductor in emerging optoelectronics. Recent works show that Ga2O3 could be a promising high- κ dielectric material due to its high thermal stability, excellent moisture resistance, and ease of processing from solution phase. However, the dielectric properties of pristine Ga2O3 could be further improved. Here, aqueous-solution-synthesized Ga2O3 with excellent dielectric properties are achieved by phosphorus (P) incorporation. Using an Ga2O3 dielectric with optimal P (20 at. %) incorporation, oxide thin-film transistors (TFTs) exhibit enhanced performance with a mobility of 20.49 ± 0.32 cm2 V−1 s−1, subthreshold swing of 0.15 ± 0.01 V/dec, current on/off ratio >106, and superior bias stress stability. Systematic analyses show that proper P incorporation considerably reduces oxygen-related defects (oxygen vacancies and hydroxyls) in Ga2O3, resulting in better dielectric and TFT performance.

MXenes are a large class of two-dimensional (2D) materials widely studied recently since they have good water solubility and are able to tune the work function (WF) of materials without changing their electronic characteristics. Based on this, aqueous solution-processed indium-free zinc tin oxide (ZTO) thin-film transistors (TFTs) have been fabricated under an annealing temperature of 300 °C and successfully optimized. This optimization is achieved by fabricating a channel layer into a homojunction structure (MXene doped ZTO/ZTO) to form a two-dimensional electron gas (2DEG). Through doping the specific concentrations of Ti3C2Tx MXenes into the upper layer ZTO thin films, the TFTs exhibit enhanced field-effect mobilities (μFE) of 10.77 cm2 V−1 s−1 and 13.06 cm2 V−1 s−1 as well as a large on/off current ratio of more than 108. Moreover, compared with the undoped double-layer ZTO TFTs, the homojunction devices show better stability, mainly resulting from the transformation in leading conduction mode. Finally, through applying the homojunction channel on the solution-processed aluminum oxide (AlOx) dielectric layer, the μFE exhibits a further enhanced value of 28.35 cm2 V−1 s−1. This is the first report to apply MXenes to the channel layer of TFTs and to fabricate solution-processed ZTO thin films via an aqueous solvent under 300 °C.

Au/MgZnO/nanolayered ZnO (Ga-doped)/In MIS (metal–insulator–semiconductor) structure UV detectors are fabricated by the PLD (pulsed laser deposition) method, and the effect of different thickness G...

Transparent amorphous oxide semiconductor (TAOS) represented by a-InGaZnO (IGZO) has achieved their commercial success in the display industry due to its superior material properties (e.g. high mobility (>10 cm 2 V −1 s −1 ), good transparency and excellent uniformity). However, TAOSs with excellent electrical properties are all n-type due to the particular electronic structures of oxide materials. The absence of high performance p-type TAOS limits the device application such as complimentary circuit and is now the largest drawback for oxide electronics. Here, we propose a low-temperature solution method to fabricate p-type transparent amorphous nickel oxide (NiO). The influence of processing parameters such as annealing temperature, precursor concentration, source/drain electrode, and dielectric layer is systematically investigated to maximum the NiO device performance. The optimized NiO TFT exhibits outstanding p-channel behavior, including a high hole mobility of 6.0 cm 2 V −1 s −1 , remarkable on/off current modulation ratio of ∼10 7 , and good subthreshold swing of 0.13 V/decade. The high performance NiO device is attributed to the synergistic optimization of annealing temperature, channel thickness, source/drain electrodes, and dielectric materials. The properties of our p-type TAOS are comparable with that of traditional n-type TAOS.

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.

We reported a low-temperature solution-processed method for the fabrication of AlOx thin films in the memory device. The detailed study is carried out to figure out the effect of varying annealing temperatures (150, 200, 250, 300, and 350 °C) on resistive switching characteristics of solution-processed aluminum oxide dielectric. The dielectric properties of AlOx films under different annealing temperatures were evaluated by atomic force microscopy (AFM), thermogravimetric analysis-differential scanning calorimetry (TGA-DSC), X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) firstly. Then the AlOx films were used as the switching dielectric layer for a variety of low-temperature solution-processed oxide resistive random access memory (RRAM) devices. It was found that forming voltage increased with increasing annealing temperature and forming free behavior could be achieved by 200 °C sample. No repeatable resistance switching characteristics were observed in the devices with minimum (150 °C) and maximum (350 °C) annealing temperatures. Compared with the ALD-derived AlOx based RRAM devices in previous study, enhanced performance like small forming voltage, large resistance ratio (〈1 8 0) and narrow resistance and voltage distribution was achieved by the solution-processed AlOx based ones at the optimized low annealing temperatures of 200 to 250 °C, which would be applied in the bionic circuit simulated by synapses and neural networks. All three samples (200, 250, and 300 °C) obtained switching endurance up to 300 cycles and data retention over 104 s. Furthermore, the solution based fabrication method also has the potential in the flexible memory application due to the merit of the low-temperature process.

Zn1-xCdxO films with different Cd contents obtained by controlling the growth oxygen pressure (Op) were deposited on both c-sapphire (Al2O3) substrates and p-GaN substrates, by means of the pulsed laser deposition (PLD) method. Photoluminescence (PL) measurement revealed that the variation of Op influenced the amount of Cd doping into Zn1-xCdxO films deposited on Al2O3, leading tunable luminescence from the ultraviolet (UV) to blue emission extended to the green band. Then all the fabricated n-Zn1-xCdxO/p-GaN heterojunction possessed good ohmic contacts and exhibited typical rectifying characteristic of the diode. Indeed, the high luminescence from the ZnCdO layer could be attained by inserting a MgO insulator to the heterojunction interface. The fabrication of tunable n-Zn1-xCdxO/p-GaN heterojunction light-emitting diodes is available which was supported by the results of electroluminescence (EL) experiment.

Room-temperature-fabricated amorphous Ga2O3 is an inexpensive and highly sensitive material for high-performance solar-blind ultraviolet (UV) (220–280 nm) detectors, which are extremely useful given the widespread use of solar-blind UV photoelectronic technology in multiple areas. The UV detection characteristics of room-temperature deposited amorphous Ga2O3 thin films fabricated by a simple RF magnetron sputtering method were studied, and the deposition Ar pressure of an a-Ga2O3 thin film was varied to determine the mechanism underlying high-performance UV detection and to develop an ideal a-Ga2O3 thin film for UV detection. A high-response amorphous Ga2O3-based UV detector was made at 0.5 Pa, and the maximum response of the device reached 436.3 A W−1 under 240 nm UV light with a 25 V bias voltage, which is near the maximum values for a single-crystal β-Ga2O3 material deposited at a high temperature. An amorphous Ga2O3-based UV detector with a low Idark noise level (4.9 nA at 25 V) and a high Iuv/Idark ratio (107314.4) was made at 1.2 Pa, and the Iuv/Idark ratio of the device was near that of a UV detector based on single-crystal β-Ga2O3 with a complex metal-oxide–semiconductor field-effect transistor (MOSFET) structure. Through a comparative analysis of the electrical characteristics and the gain mechanism within amorphous Ga2O3 thin films deposited at different Ar pressures, the high UV response of the amorphous Ga2O3 detector at 0.5 Pa is found to mainly result from the quasi-Zener tunneling multiplication phenomenon between different resistance components. The low Idark value and the high signal-to-noise ratio of the amorphous Ga2O3-based detector deposited at 1.2 Pa were mainly due to more high-resistance components and a relatively higher tunneling gain in the device. In addition, the amorphous Ga2O3-based detectors showed a much shorter response time (0.08 μs for the device deposited at 0.65 Pa) and recovery time (td1 = 0.21 ms, td2 = 5.88 ms for the device deposited at 1.2 Pa) than the reported crystal semiconductor-based devices and multiple complex structure devices. Thus, the room-temperature-fabricated amorphous Ga2O3 thin film could quickly and effectively detect a faint UV light signal in the presence of a very noisy background, which is extremely important in the applications of UV detectors in wearable, flexible photoelectronic devices.

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.

High performance UV detector with both high response and fast speed is hard to made on homogeneous crystal semiconductor materials. Here, the UV response characteristics of mix-phase MgZnO thin films with different internal structure distribution are studied, the mix-phase MgZnO based detector with given crystal composition own high response at both deep UV light (96 A/W at 240nm) and near UV light (80 A/W at 335nm). Meanwhile, because of quasi-tunneling breakdown mechanism within the device, the high response UV detector also show fast response speed (t