Development of new two-dimensional (2D) materials with high performance photoelectronic properties is critical for the future multifunctional and miniaturized optoelectronic devices. α-MnTe is an room-temperature antiferromagnetic, direct band gap p-type semiconductor with unique energy band structure and may have high photoelectric conversion efficiency and excellent photoelectric properties. However, controlled synthesis of the 2D α-MnTe single crystal has rarely been achieved so far. In this paper, 2D α-MnTe nanosheets with a NiAs-type hexagonal structure, a stable 2D nonlayered p-type semiconductor, are prepared for the first time via van der Waals epitaxy chemical vapor deposition (CVD) on mica. The thickness of 2D α-MnTe can be well tuned by the reaction temperature and gas flow. The photoelectric performance of the photodetector based on the 2D α-MnTe nanosheet shows that the 2D α-MnTe nanosheet based photodetector has an ultrahigh photoresponsivity (2599 A/W), external quantum efficiency (EQE, 8.065 × 105%), and excellent photodetectivity (3.32 × 1012 jones) at an illumination of 400 nm @ 0.062 mW/cm2 at 3 V, which is one of best performances of 2D material based photodetectors. Our work provides a new avenue to high performance 2D optoelectronic devices.

The detection of broadband spectroscopy is a huge challenge for modern optoelectronics, especially for extremely high- or low-energy photons. For metal halide perovskites significant progress has been made in high-energy photons such as X-rays, but there is little exploration of the perovskites in the high-performance detection of low-energy photons, especially mid- or far-infrared photons. Most infrared photodetectors suffer large dark currents, and perovskite photodetectors’ performances are significantly limited by ion migration. Here, a facile solution evaporation method is developed to grow a centimeter-scale zero-dimensional (0D), lead-free perovskite Cs3Bi2I9 single crystal for high-performance mid-infrared photodetectors with ultralow dark current drifts. The 0D Cs3Bi2I9 perovskite single crystal (PSC) photodetector shows an ultralow dark current drift (1.67 × 10–17 A cm–2 V–1 s–1, 9 orders of magnitude smaller than that of MAPbI3) and ultralow power consumption (smaller than 1 pA at 1 V bias) for greatly inhibited ion migration. The photodetector achieves effective photodetection from the ultraviolet to the mid-infrared (from 343 to 4000 nm) at room temperature based on the photoelectric and photobolometric effects with the best responsivity of 3.15 mA/W and detectivity of 8.7 × 108 jones at the wavelength of 343 nm at 0.033 mW/cm2. This work opens a door for low-dimensional perovskite-based mid-infrared detectors and provides a new path for the development of infrared perovskite photonics.

The combination of topological phase and intrinsic beyond-room-temperature ferromagnetism is expected to realize the quantum anomalous Hall effect at a high temperature. However, no beyond-room-temperature intrinsic ferromagnetism has been reported in either topological insulator or topological crystalline insulator (TCI) so far. Here, we report Cr-doping in TCI-phase SnTe crystals which possess highly tunable beyond-room-temperature intrinsic ferromagnetism including T c, magnetic moment, and coercivity by varying Cr contents and crystal thickness. With the increase of the Cr content, the T c increases by 159 K from 221 to 380 K and the saturation magnetic moments increase by ∼23.6 times from 0.018 to 0.421 μB/f.u. This intrinsic beyond-room-temperature ferromagnetism is fully demonstrated by the anomalous Hall effect and magneto-optical Kerr effect in a single Cr x Sn1–x Te nanosheet. Moreover, the room-temperature tunneling magnetoresistance effect has been realized by using a Cr x Sn1–x Te flake, a Fe thin film, and a commercially compatible ultrathin AlO x tunneling barrier. This work indicates a great potential of Cr x Sn1–x Te crystals in room-temperature magnetoelectronic and spintronic devices.

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Weyl semimetals haveattracted extensive research interests due to their unique topological properties. However, photoelectric devices based on pristine semimetals with large electrical conductivity are hard to detect especially under weak light. Here, with the help of MoS 2 , a stable van der Waals semiconductor, WTe 2 /MoS 2 van der Waals heterojunctions are designed to successfully realize stable photoresponse from visible light to near-infrared. Tunable photocurrent is observed compared to pristine MoS 2 with faster response under the effect of semimetal WTe 2 . Our study illustrates the great potential of WTe 2 and other topological semimetals in photodetectors.