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Highly sensitive uncooled mid-wave infrared (MWIR) photodetectors have a very wide range of applications ranging from the sensor and image to communications. Traditional MWIR detection semiconductors require liquid nitrogen cooling to depress dark current, which impeded the wide applications of devices. Here, we report a metal electrode-enhanced double parallel BP/InSe/BP van der Waals heterostructure uncooled MWIR photodetector. The device exhibits ultrahigh light on/off ratio of 108 and a very low dark current of 0.16 pA. The competitive performance includes high photoresponsivity (R) of 27.8 A W−1, excellent specific detectivity (D*) of 3.8 × 1012 cm Hz1/2 W−1, very low noise equivalent power (NEP) of 3.7 × 10−16 W Hz−1/2, and fast response speed of τr = 3.5 μs and τd = 2.4 μs in the visible range. Notably, in the MWIR range, the light on/off ratio of ∼104, NEP of 3.0 × 10−13 W Hz−1/2, and D* of 4.8 × 109 cm Hz1/2 W−1 was realized. The work sheds light on developing a high-performance uncooled MWIR photodetector by designed band alignment. [ABSTRACT FROM AUTHOR]

Permanent magnets are applied in many large‐scale and emerging applications and are crucial components in numerous established and newly evolving technologies. Rare‐earth magnets exhibit excellent hard magnetic properties; however, their applications are limited by the price and supply risk of the strategic rare‐earth elements. Therefore, there is an increasing demand for inexpensive magnets without strategic elements. Here, the authors report the intrinsic highly‐anisotropic magnetic properties of Co and Si co‐doped single crystals (Fe1−yCoy)2P1−xSix (y ≈ 0.09). Co increases Curie temperature TC; Si doping decreases magnetocrystalline anisotropy K1 and also increases TC significantly because of the enhanced interlayer interaction. The maximum room temperature magnetocrystalline anisotropy K1 = 1.09 MJ m−3 is achieved for x = 0.22, with saturation magnetization µ0Ms = 0.96 T and TC = 506 K. The theoretical maximum energy product is one of the largest for any magnet without a rare earth or Pt. Besides its promising intrinsic magnetic properties and absence of any strategic elements, other advantages are phase stability at high temperatures and excellent corrosion resistance, which make this material most promising for permanent magnetic development that will have a positive influence in industry and daily life. [ABSTRACT FROM AUTHOR]

We investigate the magnetic and transport properties of a kagome magnet YbMn 6 Sn 6 . We have grown YbMn 6 Sn 6 single crystals having a HfFe 6 Ge 6 type structure with ordered Yb and Sn atoms, which is different from the distorted structure previously reported. The single crystal undergoes a ferromagnetic phase transition around 300 K and a ferrimagnetic transition at approximately 30 K, and the magnetic transition at low temperature may be correlated to the ordered Yb sublattice. Negative magnetoresistance has been observed at high temperatures, while the positive magnetoresistance appears at 5 K when the current is oriented out of kagome plane. We observe a large anisotropic anomalous Hall effect with the intrinsic Hall contribution of 141 Ω -1 cm -1 forσzxintand 32 Ω -1 cm -1 forσxyint, respectively. These values are similar to those in YMn 6 Sn 6 with the same anisotropy. The magnetic transition and anomalous Hall behavior in YbMn 6 Sn 6 highlights the influence of the ordered Yb atoms and rare earth elements on its magnetic and transport properties., (© 2024 IOP Publishing Ltd.)

Layered narrow bandgap quasi-two-dimensional (2D) transition metal dichalcogenides (TMDs) demonstrated excellent performance in long-wave infrared (LWIR) detection. However, the low light on/off ratio and specific detectivity ( D *) due to the high dark current of the device fabricated using a single narrow bandgap material hindered its wide application. Herein, we report a type-III broken-gap band-alignment WSe 2 /PdSe 2 van der Waals (vdW) heterostructure. The heterodiode device has a prominently low dark current and exhibits a high photoresponsivity ( R ) of 55.3 A W -1 and a high light on/off ratio >10 5 in the visible range. Notably, the WSe 2 /PdSe 2 heterodiode shows an excellent uncooled LWIR response, with an R of ∼0.3 A W -1 , a low noise equivalence power (NEP) of 4.5 × 10 -11 W Hz -1/2 , and a high D * of 1.8 × 10 8 cm Hz 1/2 W -1 . This work provides a new approach for designing high-performance room-temperature operational LWIR photodetectors.

Transition metal chalcogenides such as CoS 2 have been reported as competitive catalysts for oxygen evolution reaction. It has been well confirmed that surface modification is inevitable in such a process, with the formation of different re-constructed oxide layers. However, which oxide species should be responsible for the optimized catalytic efficiencies and the detailed interface structure between the modified layer and precatalyst remain controversial. Here, a topological CoS 2 single crystal with a well-defined exposed surface is used as a model catalyst, which makes the direct investigation of the interface structure possible. Cross-sectional transmission electron microscopy of the sample reveals the formation of a 2 nm thickness Co 3 O 4 layer that grows epitaxially on the CoS 2 surface. Thick CoO pieces are also observed and are loosely attached to the bulk crystal. The compact Co 3 O 4 interface structure can result in the fast electron transfer from adsorbed O species to the bulk crystal compared with CoO pieces as evidenced by the electrochemical impedance measurements. This leads to the competitive apparent and intrinsic reactivity of the crystal despite the low surface geometric area. These findings are helpful for the understanding of catalytic origins of transition metal chalcogenides and the designing of high-performance catalysts with interface-phase engineering.

The microstructure of quasi-one-dimensional KCr 3 As 3 (133) superconductors, which were prepared by chemical cation deintercalation from their counterpart K 2 Cr 3 As 3 (233) compounds, are investigated using scanning transmission electron microscopy. The nominal KCr 3 As 3 crystals generally exhibit irregular nanoscale 133-phase domains accompanied by an amorphous As-deficient phase and cracks as a result of alkali cation deintercalation processes. Analysis of local defective structures reveals the existence of an intermediate state in the transformation from 233 to 133 phase and a possible K-deficient 233-type structure as a nanoscale cluster. Our microscopic investigations offer insight into the microstructure of KCr 3 As 3 and the alkali metal cation deintercalation processes., (© 2021 IOP Publishing Ltd.)