Low-dimensional metal-halide perovskites have emerged as promising materials for optoelectronic synapses and neuromorphic vision systems owing to their strong light–matter interactions, tunable optoelectronic properties, and mixed ionic–electronic transport. Compared with three-dimensional counterparts, low-dimensional perovskites exhibit more powerful control over charge transport, ion migration, and optical absorption with enhanced stability. In this review, we outline the composition, dimensionality, and growth strategies of low-dimensional perovskites, emphasizing how structural engineering governs their optical and electrical properties. Their photodetection, memristive, and photo-reservoir behaviors are further discussed to form physical foundation for light-stimulated synaptic functions, including optical sensing, memory retention, and conductance modulation. We review representative optoelectronic synapses based on 0D, 1D, and 2D perovskites according to their device-level mechanisms, highlighting how dimensionality enables distinct visual functions and device architectures. Exemplary neuromorphic algorithms are discussed as well, including artificial neural networks, convolutional neural networks, spiking neural networks, recurrent neural networks, and reservoir computing, which translate perovskite synaptic responses into higher-level capabilities such as image recognition, multimodal perception, and motion detection. Finally, we catalog the remaining challenges including lead toxicity, limited lead-free performance, crystallization and device-to-device variations, ion-migration-induced instability, and options for wafer-scale patterning and addressable integration. By connecting materials design, synaptic device physics, neuromorphic algorithms, and scalable integration strategies, with perspectives on how low-dimensional perovskites can evolve from laboratory-scale optoelectronic synapses into practical platforms for next-generation artificial vision systems.
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Two-dimensional (2D) van der Waals (vdW) materials offer atomically thin, dangling-bond-free interfaces and strong electrostatic control characteristics, enabling a new paradigm for optoelectronic devices. This review focuses on vdW contact engineering and heterostructure construction. The vdW contact can suppress Fermi-level pinning, reduce contact resistance, and preserve the intrinsic properties of 2D semiconductors. Leveraging such clean interfaces, 2D vdW materials show great potential in implementing functional devices, including photodetectors, miniaturized computational spectrometers, reconfigurable devices, and neuromorphic systems. In these cases, the tunable vdW interfaces eliminate lattice-matching constraints and allow feasible heterogeneous integration. This review discusses the recent progresses and future prospects in this field, providing a guidance for realizing functional applications based on vdW device configuration.
The ferroelectricity emerging in non-polar graphene/hexagonal boron nitride (hBN) heterostructures has drawn considerable attention because of its fascinating properties and promising high-frequency electrical polarization switching. Yet, the underlying mechanism is still under debate. Here in twisted double bilayer graphene (TDBLG) aligned with its neighboring hBN, we observed two types of hysteresis-delayed hysteresis in top gate induced by the anomalous screening, and advanced hysteresis in back gate caused by the anomalous gate-tunable capacitance. To investigate the role played by moiré potential in the anomalous hysteresis, we studied a moiréless graphene heterostructure. Unexpectedly, we observed exactly the same phenomena in this control device. Our findings suggest that the anomalous ferroelectricity in graphene/hBN heterostructures may originate from the dielectric material hBN, calling for further structural investigations on hBN. Further analysis indicates that those hysteresis can be asymmetric and scalable with applied external electric fields, distinct from conventional ferroelectric switching with well-defined coercive fields. The observation of gate-tunable capacitance provides more insights in the mysterious ferroelectricity in graphene/hBN heterostructures, and should enable new design of memory devices such as memcapacitor based on tunable capacitance.
Visualizing the growth of two-dimensional materials is crucial for clarifying growth mechanisms and enabling controllable synthesis. Recent in situ electron microscopy has captured atomic-scale images of MoS2 growth, extending studies beyond post-growth characterization and theoretical simulations. Yet it remains unclear whether behavior observed under the demanding conditions of transmission electron microscopy and low vapor pressure applies to macroscopic vapor-phase synthesis. Here, we use in situ optical microscopy, Raman spectroscopy, electron microscopy, and device measurements to track the complete temperature-dependent conversion pathway of two-dimensional MoO2 nanosheets into MoS2 during sulfurization. The transformation is not a direct one-step phase transition. Rather, it follows a multistep pathway involving surface nucleation, formation of an amorphous Mo−S−O intermediate, local structural ordering, and final crystallization into layered MoS2. Partially sulfurized samples retain structural asymmetry, including an intermediate phase, voids, strain, and moiré fringes, while fully sulfurized samples form uniform layered crystals. Device measurements show that this structural evolution is accompanied by a transport transition from metallic MoO2 to semiconducting MoS2. Moreover, exfoliated MoS2 from partially sulfurized samples preserves local asymmetry and exhibits a pronounced pyroelectric effect under illumination, linking the conversion pathway with optoelectronic functionality.
Bismuth-based oxides are well known for their high Curie temperature and excellent fatigue resistance, which have attracted extensive researches and various applications. In this work, we successfully fabricated pure phase α-Bi2O3 films by a novel ultraviolet ozone oxidation method from β-Bi. The obtained α-Bi2O3 exhibits room-temperature out-of-plane ferroelectricity, as confirmed by both piezoelectric force microscopy measurements and hysteresis loops obtained from out-of-plane ferroelectric tunnel junctions. Density functional calculations predict that the ferroelectricity of α-Bi2O3 arises from a synergistic interplay between electric-field-induced structural deformation and charge redistribution within films. Our results demonstrate that such a thin room-temperature ferroelectric α-Bi2O3 film could be a promising candidate for future multifunctional electronic devices.
Bismuth sulfide (Bi2S3), a widely studied photocatalytic material, has attracted increasing interest for optoelectronic applications because of its strong light absorption and suitable bandgap. However, the photoelectric properties of single-crystalline Bi2S3 remain insufficiently explored, mainly due to the difficulty in synthesizing high-quality ultrathin crystals suitable for device integration. Here, we report the low-pressure chemical vapor deposition (LPCVD) growth of ultrathin single-crystalline Bi2S3 nanosheets with thicknesses of approximately 40–60 nm and demonstrate high-performance gate-tunable photodetectors based on back-gated field-effect transistor (FET) devices. Under 630 nm illumination, the devices deliver a high responsivity of 67.36 A·W−1, an external quantum efficiency (EQE) of 52618%, and a detectivity on the order of 1012 Jones. These metrics outperform previously reported Bi2S3 photodetection devices and highlight the great potential of LPCVD-grown Bi2S3 for high-speed and high-sensitivity photodetection. Combined with its tunable bandgap and structural anisotropy, Bi2S3 represents a promising material platform for next-generation photodetectors, image sensors and integrated optoelectronic technologies.
Bi2O2Se is a high-mobility, narrow-bandgap n-type layered semiconductor promising for broadband photodetection. However, its synthesis often relies on high temperatures or complex precursor systems that increase the thermal budget and limit device integration. Here we report a low-melting-point precursor-assisted chemical vapor deposition (CVD) strategy for growing high-quality Bi2O2Se nanosheets at 450 °C. Using elemental Bi and Se powders under an Ar/O2 atmosphere, we obtain single-crystalline nanosheets with uniform composition, long-term air stability and lateral sizes up to 0.6 mm. Photodetectors fabricated from the nanosheets show broadband response from 520 to 1550 nm, with a responsivity of 14.17 A∙W−1 and a specific detectivity of 6.39 × 1010 Jones at 1550 nm. The devices also exhibit fast response, with rise and fall times of 59 and 67 μs, respectively. Single-pixel imaging at 520 and 1550 nm further demonstrates their visible and near-infrared imaging capability. This work establishes low-melting-point precursor-assisted CVD as an effective route for low-temperature Bi2O2Se growth and points to its potential in broadband, high-speed photodetection.
CdZnTe films show great promise for applications in infrared imaging, solar cells, and radiation detection due to their excellent optoelectronic properties. However, single-crystal CdZnTe films directly deposited on commercial GaAs (001) substrate suffer from a high density of crystalline defects caused by a large lattice mismatch. Here we report the epitaxial growth of single-crystal CdZnTe films on GaAs (001) substrate using close spaced sublimation with a single-crystal ZnTe thin film as a buffer layer. As-grown CdZnTe films exhibit higher crystalline quality than those grown without a buffer layer. The optimal substrate temperature range is found to be 370−390 °C, and the growth rate reaches 94 μm/h. This work provides an approach to grow high-quality single-crystal CdZnTe films for optoelectronic device applications.
Achieving simultaneous phase stabilization and ultralow leakage remains a fundamental challenge for ZrO2-based high-k dielectrics. This work demonstrates high-performance 5.7 nm ZrO2-based metal−insulator−metal capacitors through coordinated interfacial engineering and defect passivation. The AlZrO alloy interfacial layer preserves lattice coherence and provides an interfacial barrier while stabilizing the anti-ferroelectric tetragonal phase ZrO2, enabling an equivalent oxide thickness of 0.89 nm. Subsequent in-situ remote O2 plasma treatment passivates oxygen vacancies via radical oxidation without inducing plasma damage. As a result, the capacitors achieve an ultralow leakage current density of 3 × 10−10 A/cm2 at 1 V, a breakdown voltage exceeding 5 V, and a projected 10-year operating voltage above 2.4 V based on time-dependent dielectric breakdown extrapolation. All processes are conducted below 350 °C, ensuring back-end-of-line (BEOL) compatibility. These results demonstrate a pathway toward simultaneous dielectric constant enhancement, leakage suppression, and long-term reliability in ultrathin ZrO2-based high-k dielectrics.
