Transition metal dichalcogenide nanostructures especially MoS2 have emerged as novel gas sensing materials. Particularly, MoS2-based optoelectronic devices activated by UV or visible light have been demonstrated as promising candidates for room temperature NO2 sensors. Here, we propose a novel room-temperature optoelectronic NO2 sensor based on sulfur-vacancy-enriched MoS2 (SV-MoS2). SV-MoS2 nanosheets were efficiently fabricated by a microwave-hydrothermal method, and their enhanced optical absorption and optoelectronic properties in the near-infrared (NIR) light region were experimentally and theoretically investigated. The optoelectronic gas sensors based on SV-MoS2 exhibited enhanced performance to ppb level of NO2 under NIR light illumination at room temperature. In addition, through functionalization with ZnO quantum dots, the SV-MoS2/ZnO nanocomposites exhibited a further enhancement in responses with fast response/recovery rates, full reversibility, and sub-ppb detection limit to NO2 at room temperature. The significant NO2 sensing improvement was due to the improved charge generation and transfer induced by sulfur vacancy under NIR light illumination. In addition, the sensor shows satisfied stability, reliable selectivity, and humidity resistance at room temperature. Therefore, this work provides an alternative approach to high-performance, low-power-consumption optoelectronic NO2 gas sensors working at room temperature, which can also be applied to other transition metal dichalcogenides for optoelectronic devices.

A magnetic heterostructure with good thermal stability, large damping‐like spin–obit torque (DL‐SOT), and low power consumption is crucial to realize thermally stable, fast, and efficient magnetization manipulation in SOT devices. This work systematically investigates on PtxCu1‐x/Co/MgO magnetic heterostructures with perpendicular magnetic anisotropy (PMA), and reports a promising spin Hall material, Pt–Cu alloy, possessing large DL‐SOT efficiency and moderate resistivity. The optimal Pt0.57Cu0.43 has a large DL‐SOT efficiency of about 0.44, as determined by hysteresis loop shift measurements, with a relatively low resistivity (82.5 µΩ cm at 5 nm thickness). Moreover, this large DL‐SOT efficiency and the coercivity reduction accompanying with proper alloying contribute to a low critical switching current density (2.37 × 106 A cm−2 in the Pt0.57Cu0.43 layer) in current‐induced magnetization switching measurements. Finally, the thermal stability of the Co layer can be preserved under alloying, whereas the switching power consumption can be significantly reduced, being the best performance among reported Pt‐based spin current sources. This systematic study on SOT switching properties suggests that Pt0.57Cu0.43 is an attractive spin current source with moderate resistivity, large DL‐SOT efficiency, good thermal stability, and low power consumption for future SOT applications.

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5d transition metal Pt is the canonical spin Hall material for efficient generation of spin−orbit torques (SOTs) in Pt/ferromagnetic layer (FM) heterostructures. However, for a long while with tremendous engineering endeavors, the damping-like SOT efficiencies (ξ DL ) of Pt and Pt alloys have still been limited to ξ DL < 0.5. Here we present that with proper alloying elements, particularly 3d transition metals V and Cr, a high spin−orbital Hall conductivity (σ SH ≈ 6.5 × 10 5 (ℏ/2e) Ω −1 m −1 ) can be developed. Especially for the Cr-doped case, an extremely high ξ DL ≈ 0.9 in a Pt 0.69 Cr 0.31 / Co device can be achieved with a moderate Pt 0.69 Cr 0.31 resistivity of ρ xx ≈ 133 μΩ cm. A low critical SOT-driven switching current density of J c ≈ 3.2 × 10 6 A cm −2 is also demonstrated. The damping constant (α) of the Pt 0.69 Cr 0.31 /FM structure is also found to be reduced to 0.052 from the pure Pt/FM case of 0.078. The overall high σ SH , giant ξ DL , moderate ρ xx , and reduced α of such a Pt−Cr/FM heterostructure makes it promising for versatile extremely low power consumption SOT memory applications.