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Various large-area growth methods for two-dimensional transition metal dichalcogenides have been developed recently for future electronic and photonic applications. However, they have not yet been employed for synthesizing active pixel image sensors. Here, we report on an active pixel image sensor array with a bilayer MoS 2 film prepared via a two-step large-area growth method. The active pixel of image sensor is composed of 2D MoS 2 switching transistors and 2D MoS 2 phototransistors. The maximum photoresponsivity ( R ph ) of the bilayer MoS 2 phototransistors in an 8 × 8 active pixel image sensor array is statistically measured as high as 119.16 A W −1 . With the aid of computational modeling, we find that the main mechanism for the high R ph of the bilayer MoS 2 phototransistor is a photo-gating effect by the holes trapped at subgap states. The image-sensing characteristics of the bilayer MoS 2 active pixel image sensor array are successfully investigated using light stencil projection. Here, the authors report the realization of an active pixel image sensor array composed by 64 pairs of switching transistors and phototransistors, based on wafer-scale bilayer MoS 2 . The device exhibits sensitive photoresponse under RGB light illumination, showing the potential of 2D MoS 2 for image sensing applications.

Incipient ferroelectricity bridges traditional dielectrics and true ferroelectrics, enabling advanced electronic and memory devices. Firstly, we report incipient ferroelectricity in freestanding SrTiO 3 nanomembranes integrated with monolayer MoS 2 to create multifunctional devices, demonstrating stable ferroelectric order at low temperatures for cryogenic memory devices. Our observation includes ultra-fast polarization switching (~10 ns), low switching voltage (<6 V), over 10 years of nonvolatile retention, 100,000 endurance cycles, and 32 conductance states (5-bit memory) in SrTiO 3 -gated MoS 2 transistors at 15 K and up to 100 K. Additionally, we exploit room-temperature weak polarization switching, a feature of incipient ferroelectricity, to construct a physical reservoir for pattern recognition. Our results showcase the potential of utilizing perovskite material properties enabled by advancements in freestanding film growth and heterogeneous integration, for diverse functional applications. Notably, the low 180 °C thermal budget for fabricating the 3D-SrTiO 3 /2D-MoS 2 device stack enables the integration of diverse materials into silicon complementary metal-oxide-semiconductor technology, addressing challenges in compute-in-memory and neuromorphic applications. Sen et al. report the stacking of a perovskite incipient ferroelectric nanomembrane with atomically thin 2D material for a back-end-of-line compatible ferroelectric-like field effect transistors, functioning as a cryogenic memory at 15 K and as an inference engine at room temperature.

Highly sensitive and system integrable gas sensors play a significant role in industry and daily life, and MoS2 has emerged as one of the most promising two-dimensional nanomaterials for gas sensor technology. In this study, we demonstrate a scalable and monolithically integrated active-matrix gas sensor array based on large-area bilayer MoS2 films synthesized via two-successive steps: radio-frequency magnetron sputtering and thermal sulfurization. The fabricated thin-film transistors exhibit consistent electrical performance over a few centimeters area and resulting gas sensors detect NO2 with ultra-high sensitivity across a wide detection range, from 1 to 256 ppm. This is due to the abundant grain boundaries of the sputtered MoS2 channel, which perform as active sites for absorption of NO2 gas molecules. The demonstrated active-matrix gas sensor arrays display good switching capabilities and are anticipated to be readily integrated with additional circuitry for different gas sensing and monitoring applications.Sensitive and scalable gas sensors are essential in daily life air-quality monitoring. Here, a monolithically integrated gas sensing circuit based on two-step-grown polycrystalline MoS2 films is fabricated, showing good switching and NO2 gas sensing response in a wide detection range of 1 to 256 ppm.

Incipient ferroelectricity bridges traditional dielectrics and true ferroelectrics, enabling advanced electronic and memory devices. Firstly, we report incipient ferroelectricity in freestanding SrTiO nanomembranes integrated with monolayer MoS to create multifunctional devices, demonstrating stable ferroelectric order at low temperatures for cryogenic memory devices. Our observation includes ultra-fast polarization switching (~10 ns), low switching voltage (<6 V), over 10 years of nonvolatile retention, 100,000 endurance cycles, and 32 conductance states (5-bit memory) in SrTiO -gated MoS transistors at 15 K and up to 100 K. Additionally, we exploit room-temperature weak polarization switching, a feature of incipient ferroelectricity, to construct a physical reservoir for pattern recognition. Our results showcase the potential of utilizing perovskite material properties enabled by advancements in freestanding film growth and heterogeneous integration, for diverse functional applications. Notably, the low 180 °C thermal budget for fabricating the 3D-SrTiO /2D-MoS device stack enables the integration of diverse materials into silicon complementary metal-oxide-semiconductor technology, addressing challenges in compute-in-memory and neuromorphic applications.

Various large-area growth methods for two-dimensional transition metal dichalcogenides have been developed recently for future electronic and photonic applications. However, they have not yet been employed for synthesizing active pixel image sensors. Here, we report on an active pixel image sensor array with a bilayer MoS film prepared via a two-step large-area growth method. The active pixel of image sensor is composed of 2D MoS switching transistors and 2D MoS phototransistors. The maximum photoresponsivity (R ) of the bilayer MoS phototransistors in an 8 × 8 active pixel image sensor array is statistically measured as high as 119.16 A W . With the aid of computational modeling, we find that the main mechanism for the high R of the bilayer MoS phototransistor is a photo-gating effect by the holes trapped at subgap states. The image-sensing characteristics of the bilayer MoS active pixel image sensor array are successfully investigated using light stencil projection.

Water-soluble sacrificial layers based on epitaxially-grown, single crystalline (Ca, Sr, Ba)3Al2O6 layer are widely used for creating free-standing perovskite oxide membranes. However, obtaining these sacrificial layers with intricate stoichiometry remains a challenge, especially for molecular beam epitaxy (MBE). In this study, we demonstrate the hybrid MBE growth of epitaxial, single crystalline SrTiO3 films using a solution processed, amorphous SrCa2Al2O6 sacrificial layer onto SrTiO3 (001) substrates. Prior to the growth, the oxygen plasma exposure was used to first create the crystalline SrCa2Al2O6 layer with well-defined surface crystallinity. Utilizing reflection high energy electron diffraction, x-ray diffraction, and atomic force microscopy, we observe an atomic layer-by-layer growth of epitaxial, single crystalline SrTiO3 film on the SrCa2Al2O6 layer with atomically smooth surfaces. The SrCa2Al2O6 layer was subsequently dissolved in de-ionized water to create free-standing SrTiO3 membranes that were transferred onto a metal-coated Si wafer. Membranes created with Sr-deficiency revealed ferroelectric-like behavior measured using piezo force microscopy whereas stoichiometric films remained paraelectric-like. These findings underscore the viability of using ex-situ deposited amorphous SrCa2Al2O6 for epitaxial, single crystalline growth, as well as the importance of point defects in determining the ferroic properties in membranes.

The advancement in thin-film exfoliation for synthesizing oxide membranes has opened up new possibilities for creating artificially-assembled heterostructures with structurally and chemically incompatible materials. The sacrificial layer method is a promising approach to exfoliate as-grown films from a compatible material system, allowing their integration with dissimilar materials. Nonetheless, the conventional sacrificial layers often possess intricate stoichiometry, thereby constraining their practicality and adaptability, particularly when considering techniques like Molecular Beam Epitaxy (MBE). This is where easy-to-grow binary alkaline earth metal oxides with a rock salt crystal structure are useful. These oxides, which include (Mg, Ca, Sr, Ba)O, can be used as a sacrificial layer covering a much broader range of lattice parameters compared to conventional sacrificial layers and are easily dissolvable in deionized water. In this study, we show the epitaxial growth of single-crystalline perovskite SrTiO3 (STO) on sacrificial layers consisting of crystalline SrO, BaO, and Ba1-xCaxO films, employing a hybrid MBE method. Our results highlight the rapid (< 5 minutes) dissolution of the sacrificial layer when immersed in deionized water, facilitating the fabrication of millimeter-sized STO membranes. Using high-resolution x-ray diffraction, atomic-force microscopy, scanning transmission electron microscopy, impedance spectroscopy, and scattering-type near-field optical microscopy (SNOM), we demonstrate epitaxial STO membranes with bulk-like intrinsic dielectric properties. The employment of alkaline earth metal oxides as sacrificial layers is likely to simplify membrane synthesis, particularly with MBE, thus expanding research possibilities.

The epitaxial growth of functional materials using a substrate with a graphene layer is a highly desirable method for improving structural quality and obtaining free-standing epitaxial nano-membranes for scientific study, applications, and economical reuse of substrates. However, the aggressive oxidizing conditions typically employed to grow epitaxial perovskite oxides can damage graphene. Here, we demonstrate a technique based on hybrid molecular beam epitaxy that does not require an independent oxygen source to achieve epitaxial growth of complex oxides without damaging the underlying graphene. The technique produces films with self-regulating cation stoichiometry control and epitaxial orientation to the oxide substrate. Furthermore, the films can be exfoliated and transferred to foreign substrates while leaving the graphene on the original substrate. These results open the door to future studies of previously unattainable free-standing nano-membranes grown in an adsorption-controlled manner by hybrid molecular beam epitaxy, and has potentially important implications for the commercial application of perovskite oxides in flexible electronics.

We retrospectively assessed the results of performing ethanol embolization for pelvis arteriovenous malformations (AVMs). During the past 10 years, eight patients (8 females, age range: 27-52 years) with AVMs in the pelvic wall (n = 3) and uterus (n = 5) underwent staged ethanol embolizations (range: 1-5, mean: 2.5) under general anesthesia. Ethanol embolization was performed by the use of the transcatheter and/or direct puncture techniques. Clinical follow-up was performed for all of the patients, and imaging follow-up was available for seven patients. The therapeutic outcomes were established by evaluating the clinical outcome of the signs and symptoms, as well as the degree of devascularization observed on post-procedural angiography. During the 20 sessions of ethanol embolization, the solitary transarterial approach was used 14 times, the transvenous approach was used three times and direct puncture was used once. For two patients, the transarterial and transvenous or direct puncture approaches were used together in one session. For four patients, ethanol and coils were used as embolic agents, and n-butyl cyanoacrylate (NBCA) and ethanol were used in one patient. Seven (88%) of eight patients were cured of their AVMs and one patient (12%) displayed improvement. Major complications were seen in two patients (25%). Ethanol embolization is effective for the treatment of pelvic arteriovenous malformations, though there is a chance of a major complication.