Atomically thin 2D layered transition metal dichalcogenides (TMDs) have been extensively studied in recent years because of their appealing electrical and optical properties. Here, the fabrication of ReS2 field‐effect transistors is reported via the encapsulation of ReS2 nanosheets in a high‐κ Al2O3 dielectric environment. Low‐temperature transport measurements allow to observe a direct metal‐to‐insulator transition originating from strong electron–electron interactions. Remarkably, the photodetectors based on ReS2 exhibit gate‐tunable photoresponsivity up to 16.14 A W−1 and external quantum efficiency reaching 3168%, showing a competitive device performance to those reported in graphene, MoSe2, GaS, and GaSe‐based photodetectors. This study unambiguously distinguishes ReS2 as a new candidate for future applications in electronics and optoelectronics.

Charge-trap memory with high-κ dielectric materials is considered to be a promising candidate for next-generation memory devices. Ultrathin layered twodimensional (2D) materials like graphene and MoS2 have been receiving much attention because of their novel physical properties and potential applications in electronic devices. Here, we report on a dual-gate charge-trap memory device composed of a few-layer MoS2 channel and a three-dimensional (3D) Al2O3/HfO2/Al2O3 charge-trap gate stack. Owing to the extraordinary trapping ability of both electrons and holes in HfO2, the MoS2 memory device exhibits an unprecedented memory window exceeding 20 V. More importantly, with a back gate the window size can be effectively tuned from 15.6 to 21 V; the program/erase current ratio can reach up to 10 4 , far beyond Si-based flash memory, which allows for multi-bit information storage. Furthermore, the device shows a high mobility of 170 cm 2 V -1 s -1 , a good endurance of hundreds of cycles and a stable retention of ~28% charge loss after 10 years which is drastically lower than ever reported MoS2 flash memory. The combination of 2D materials with traditional high-κ charge-trap gate stacks opens up an exciting field of novel nonvolatile memory devices. KEYWORDS. Charge-trap memory, MoS 2 , Memory window, Dual gate, Memory characteristics 3 Atomically thin 2D materials like graphene and MoS 2 has been extensivelystudied recently because of their promising applications in optoelectronics 1, 2 , spintronics 3-7 , transparent and flexible devices [8][9][10][11][12] . Due to its remarkable properties, such as high carrier mobility and mechanical flexibility, graphene has been incorporated into nonvolatile memory structures serving as a floating gate 13,14 or a transparent channel 15 . However, owing to its zero band gap 16 , the graphene channeled memory devices typically possess a low program/erase current ratio, which significantly hinders its application in nonvolatile memory devices. Unlike graphene, MoS 2 has a transition from indirect band gap (1.2 eV) to a direct band gap (1.8 eV) in monolayer 17,18 . Its field effect transistors 19 show a high mobility of 200 cm 2 V -1 s -1 with a high on/off ratio approximately 10 8 . To potentially enhance the program/erase current ratio, attempts were made to replace graphene with MoS 2 as a channel material in a ferroelectric memory 20 or as a charge-trap layer in a graphene flash memory 21 . It was demonstrated that the monolayer MoS 2 is very sensitive to the presence of charges 14 . However, the relatively small memory window, the degraded mobility, and the insufficient trap capability in those devices require further improvement of the chargetrap stack in the MoS 2 memory device.

Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have been recently proposed as appealing candidate materials for spintronic applications owing to their distinctive atomic crystal structure and exotic physical properties arising from the large bonding anisotropy. Here we introduce the first MoS2-based spin-valves that employ monolayer MoS2 as the nonmagnetic spacer. In contrast with what is expected from the semiconducting band-structure of MoS2, the vertically sandwiched-MoS2 layers exhibit metallic behavior. This originates from their strong hybridization with the Ni and Fe atoms of the Permalloy (Py) electrode. The spin-valve effect is observed up to 240 K, with the highest magnetoresistance (MR) up to 0.73% at low temperatures. The experimental work is accompanied by the first principle electron transport calculations, which reveal an MR of ∼9% for an ideal Py/MoS2/Py junction. Our results clearly identify TMDs as a promising spacer compound in magnetic tunnel junctions and may open a new avenue for the TMDs-based spintronic applications.

MoS2 is a layered two-dimensional material with strong spin-orbit coupling and long spin lifetime, which is promising for electronic and spintronic applications. However, because of its large band gap and small electron affinity, a considerable Schottky barrier exists between MoS2 and contact metal, hindering the further study of spin transport and spin injection in MoS2. Although substantial progress has been made in improving device performance, the existence of metal-semiconductor Schottky barrier has not yet been fully understood. Here, we investigate permalloy (Py) contacts to both multilayer and monolayer MoS2. Ohmic contact is developed between multilayer MoS2 and Py electrodes with a negative Schottky barrier, which yields a high field-effect mobility exceeding 55 cm2V−1s−1 at low temperature. Further, by applying back gate voltage and inserting different thickness of Al2O3 layer between the metal and monolayer MoS2, we have achieved a good tunability of the Schottky barrier height (down to zero). These results are important in improving the performance of MoS2 transistor devices; and it may pave the way to realize spin transport and spin injection in MoS2.