Ferromagnetic order in 2D2D materials has triggered widespread interest because of their applications in spintronic devices. Monolayer 1T-VSe 2 , as a recently emerged candidate of 2D2D ferromagnetic material, exhibits complicated behaviors that contradict the theoretical predictions. In this work, a systematic investigation is presented on the evolution of the transport properties in VSe 2 thin flakes controlled by gate voltage. Notably, for the first time, a paramagnetic-to-ferromagnetic transition is realized in a VSe 2 thin flake using a field-effect transistor setup with solid ion conductor of polycrystalline Li 1+ x + y Al x (Ti 2− y Ge y )P 3− z Si z O 12 serving as the gate dielectric. The Curie temperature determined from the electrical transport measurements is ≈40 K. The electric-field-controlled ferromagnetism in exfoliated VSe 2 flakes provides an excellent platform for developing advanced spintronics as well as investigating unusual emergent physics in 2D systems.
VSe 2 is a promising anode material for Li-ion batteries (LIBs) due to its unique layered structure, and its metallic properties. However, further exploration to investigate the lithium storage performance of VSe 2 is limited by the synthesis difficulty of pure VSe 2 . In this work, a novel nitrogen-doped carbon modified VSe 2 obtained by using p -phenylenediamine as the reducing agent is reported. This material delivers a reversible capacity of 738.25 mA h g −1 at 100 mA g −1 and after 50 cycles, it retains 772.15 mA h g −1 . Using p -phenylenediamine as a reducing agent to obtain VSe 2 is demonstrated for the first time, and p -phenylenediamine also provides carbon and nitrogen sources for the heteroatom modification of VSe 2 . This modification of nitrogen-doped carbon facilitates the generation of new active sites, and improve charge transfer. First-principle calculations show that the diffusion barrier for the Li + migration within the VSe 2 layers is low. The ex-situ X-ray diffraction (XRD) results verify that VSe 2 stores lithium through intercalation and conversion reactions. This work may provide a new solution for synthesizing high-performance transition metal dichalcogenide electrode materials.
Wang Tao,Shi Xinyao,Wang Jin,Xu Yijun,Chen Jie,Dong Zhuo,Jiang Man,Ma Pengfei,Su Rongtao,Ma Yanxing,Wu Jian,Zhang Kai,Zhou Pu
Vanadium diselenide (VSe 2 ), a typical metallic behaviour material among transition metal dichalcogenides (TMDCs) family, exhibits excellent photoelectric characteristics with a zero band gap, missing applicaiotn in pulse generation. In this work, a high-quality VSe 2 saturable absorber (SA) was synthesized through a liquid-phase exfoliation method. The saturable absorption of obtained VSe 2 -SA was characterized systematically. The measured modulation depth was 9.9%, and the saturated intensity was 533.8 µJ/cm 2 . By incorporating this optical modulator into a ytterbium-doped fiber laser cavity, a stable passively Q-switched laser could be achieved. The pulse had the central wavelength of 1064.03 nm. As the pump power was increased, the repetition rate increased from 24.3 kHz to 35.6 kHz, and the pulse duration decreased from 7.21 µs to 5.27 µs. The output power had the maximum value of 28.55 mW. These results indicated that VSe 2 is an effective candidate to generate pulse laser due to its excellent nonlinear optical properties and universal photoelectric response, which may advance the applications of VSe 2 -based nonlinear optics and photoelectric devices.
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