Thin film transistors (TFTs) are key components for the fabrication of electronic and optoelectronic devices, resulting in a push for the wider exploration of semiconducting materials and ...cost‐effective synthesis processes. In this report, a simple approach is proposed to achieve 2‐nm‐thick indium oxide nanosheets from liquid metal surfaces by employing a squeeze printing technique and thermal annealing at 250 °C in air. The resulting materials exhibit a high degree of transparency (>99 %) and an excellent electron mobility of ≈96 cm2 V−1 s−1, surpassing that of pristine printed 2D In2O3 and many other reported 2D semiconductors. UV‐detectors based on annealed 2D In2O3 also benefit from this process step, with the photoresponsivity reaching 5.2 × 104 and 9.4 × 103 A W−1 at the wavelengths of 285 and 365 nm, respectively. These values are an order of magnitude higher than for as‐synthesized 2D In2O3. Utilizing transmission electron microscopy with in situ annealing, it is demonstrated that the improvement in device performances is due to nanostructural changes within the oxide layers during annealing process. This work highlights a facile and ambient air compatible method for fabricating high‐quality semiconducting oxides, which will find application in emerging transparent electronics and optoelectronics.
2‐nm‐thick indium oxide nanosheets with high electron mobility have been synthesized utilizing a liquid metal printing technique and thermal annealing in air. Transmission electron microscopy with in situ annealing reveals that the improvement in device performances is due to nanostructural changes during annealing process. This work highlights a facile and ambient air compatible method for fabricating high‐quality semiconductors, which find application in emerging electronics and optoelectronics.
Optoelectronic devices based on optically responsive materials have gained significant attention due to their low cross talk and reduced power consumption. These devices rely on light‐induced changes ...in conductance states, which are used to create synaptic weights for image recognition tasks in neural networks. However, a major drawback of such devices is the rapid decay of conductance states after light stimulus removal, which hinders their long‐term memory and performance without a continuous external stimulus in place. To address this issue, a platform neural network scheme is proposed to counter the natural decay of conductance in optoelectronic devices. The approach restores the memory effect of the devices and significantly enhances their performance by several orders of magnitude without using additional energy‐intensive techniques like training pulses or gate fields. Herein, the model is validated experimentally using optoelectronic devices fabricated with two different materials, BP and doped In2O3, and demonstrates the restoration of memory/image retention ability to any material system being studied for optoelectronic synapses and vision. This approach has important implications for the practical application of neuromorphic visual processing technologies, bringing them closer to real‐world applications.
Neuromorphic photonics particularly artificial vision hardware relies on the generation of electrical current upon light excitation. This current decays over time upon stimulus removal. An adaptive neural network model that can address this intrinsic decay is reported here. This model enables longer data storage and reduces energy consumption, improving accuracy and robustness of optoelectronic neural‐mimicking hardware to variabilities.
Metal oxide-based gas sensor technology is promising due to their practical applications in toxic and hazardous gas detection. Orthorhombic α-MoO3 is a planar metal oxide with a unique layered ...structure, which can be obtained in a two-dimensional (2D) form. In the 2D form, the larger surface area-to-volume ratio of the material facilitates significantly higher interaction with gas molecules while exhibiting exceptional transport properties. The presence of oxygen vacancies results in nonstoichiometric MoO3 (MoO3–x ), which further enhances the charge carrier mobility. Here, we study dual gas sensing characteristics and mechanism of 2D α-MoO3–x . Herein, conductometric dual gas sensors based on chemical vapor deposited 2D α-MoO3–x are developed and demonstrated. A facile transfer process is established to integrate the material into any arbitrary substrate. The sensors show high selectivity toward NO2 and H2S gases with response and recovery rates of 295.0 and 276.0 kΩ/s toward NO2 and 28.5 and 48.0 kΩ/s toward H2S, respectively. These gas sensors also show excellent cyclic endurance with a variation in ΔR ∼ 112 ± 1.64 and 19.5 ± 1.13 MΩ for NO2 and H2S, respectively. As such, this work presents the viability of planar 2D α-MoO3–x as a dual selective gas sensor.
Chromism-based optical filters is a niche field of research, due to there being only a handful of electrochromic materials. Typically, electrochromic transition metal oxides such as MoO3 and WO3 are ...utilized in applications such as smart windows and electrochromic devices (ECD). Herein, we report MoO3–x -based electrically activated ultraviolet (UV) filters. The MoO3–x grown on indium tin oxide (ITO) substrate is mechanically assembled onto an electrically activated proton exchange membrane. Reversible H+ injection/extraction in MoO3–x is employed to switch the optical transmittance, enabling an electrically activated optical filter. The devices exhibit broadband transmission modulation (325–800 nm), with a peak of ∼60% in the UV-A range (350–392 nm). Comparable switching times of 8 s and a coloration efficiency of up to 116 cm2 C–1 are achieved.
Availability of computing will be strongly limited by global energy production in 1–2 decades. Computing consumes 4–5% of global electricity supply and continues to increase. This is underpinned by ...memory and switching devices encountering leakage as they are downscaled. Two‑dimensional (2D) materials offer a potential solution to the fundamental problem owing to carrier confinement which significantly reduces scattering events. Herein, a mixed ionic‑electronic transport is used in layered black phosphorus (BP) based vertically stacked resistance change memories. The memory device relies on a unique interplay between the oxygen and silver ion diffusion through the stack which is generated using a combination of bottom (electrochemically active silver) and top (indium tin oxide) electrodes. The use of a transparent top‐electrode enabled for the first time to conduct spectroscopic characterization of the device and experimentally reveal fundamental mechanisms. Endurance of the devices are observed to be >104 switching cycles, with ON/OFF current ratio of >107 and standby power consumption of <5 fW, which effectively suppresses leakage current and sneak paths in a memory array. By undertaking detailed microscopic and spectroscopic investigations, supported by theoretical calculations, this work opens opportunities to enhance resistive switching performances of 2D materials for next‑generation information storage and brain‑inspired computation.
The use of 2D materials in resistance change memories offer a potential solution to challenges faced by next‐generation data storage technologies. Engineering mixed ionic‐electronic transport in 2D black phosphorus based vertically stacked memory addresses reliability and standby power consumption issues. Previously invisible localized switching spot is revealed nondestructively with high spatial resolution by a Raman mapping technique.
Miniaturization and energy consumption by computational systems remain major challenges to address. Optoelectronics based synaptic and light sensing provide an exciting platform for neuromorphic ...processing and vision applications offering several advantages. It is highly desirable to achieve single‐element image sensors that allow reception of information and execution of in‐memory computing processes while maintaining memory for much longer durations without the need for frequent electrical or optical rehearsals. In this work, ultra‐thin (<3 nm) doped indium oxide (In2O3) layers are engineered to demonstrate a monolithic two‐terminal ultraviolet (UV) sensing and processing system with long optical state retention operating at 50 mV. This endows features of several conductance states within the persistent photocurrent window that are harnessed to show learning capabilities and significantly reduce the number of rehearsals. The atomically thin sheets are implemented as a focal plane array (FPA) for UV spectrum based proof‐of‐concept vision system capable of pattern recognition and memorization required for imaging and detection applications. This integrated light sensing and memory system is deployed to illustrate capabilities for real‐time, in‐sensor memorization, and recognition tasks. This study provides an important template to engineer miniaturized and low operating voltage neuromorphic platforms across the light spectrum based on application demand.
Optoelectronic vision and synaptic devices can help overcome high energy requirements of computation and enable miniaturised, precise, real‐time vision systems. Herein, atomically thin layers of Sb doped In2O3 are utilised as ultraviolet‐active optoelectronic synapses with recognition and prolonged memory capabilities. The material is devised into an imaging array of photo‐active pixels capable of pattern recognition and memorization at low power with very few training cycles.
Abstract Molybdenum disulfide (MoS 2 ), a two‐dimensional (2D) semiconducting material harbors intrinsic defects that can be harnessed to achieve tuneable electronic, optoelectronic, and ...electrochemical devices. However, achieving precise control over defect formation within monolayer MoS 2 , remains a notable challenge. Here, an in‐situ defect engineering approach for monolayer MoS 2 using a pressure‐dependent chemical vapor deposition (CVD) process is presented. Monolayer MoS 2 grown in a low pressure CVD conditions (LP‐MoS 2 ) produces sulfur vacancy ( V s ) induced defect‐rich crystals primarily attributed to the oxygen‐deficient growth conditions. Conversely, atmospheric pressure CVD‐grown MoS 2 (AP‐MoS 2 ) passivates these defects with oxygen from ambient conditions. This disparity in defect profiles profoundly impacts crucial functional properties and device performance. AP‐MoS 2 shows a drastically enhanced photoluminescence, which is significantly quenched in LP‐MoS 2 attributed to in‐gap electron donor states induced by the V s defects. However, the n‐doping induced in LP‐MoS 2 generates enhanced photoresponsivity and detectivity in fabricated photodetectors compared to the AP‐MoS 2 ‐based devices. Defect‐rich LP‐MoS 2 outperforms AP‐MoS 2 as channel layers of field‐effect transistors (FETs), as well as electrocatalytic material for hydrogen evolution reaction (HER). This work presents a single‐step CVD approach for in situ defect engineering in monolayer MoS 2 and presents a pathway to control defects in other monolayer 2D materials.
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