Two-dimensional materials provide extraordinary opportunities for exploring phenomena arising in atomically thin crystals. Beginning with the first isolation of graphene, mechanical exfoliation has been a key to provide high-quality two-dimensional materials, but despite improvements it is still limited in yield, lateral size and contamination. Here we introduce a contamination-free, one-step and universal Au-assisted mechanical exfoliation method and demonstrate its effectiveness by isolating 40 types of single-crystalline monolayers, including elemental two-dimensional crystals, metal-dichalcogenides, magnets and superconductors. Most of them are of millimeter-size and high-quality, as shown by transfer-free measurements of electron microscopy, photo spectroscopies and electrical transport. Large suspended two-dimensional crystals and heterojunctions were also prepared with high-yield. Enhanced adhesion between the crystals and the substrates enables such efficient exfoliation, for which we identify a gold-assisted exfoliation method that underpins a universal route for producing large-area monolayers and thus supports studies of fundamental properties and potential application of two-dimensional materials.

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The discovery of ferromagnetic two-dimensional van der Waals materials has opened up opportunities to explore intriguing physics and to develop innovative spintronic devices. However, controllable synthesis of these 2D ferromagnets and enhancing their stability under ambient conditions remain challenging. Here, we report chemical vapor deposition growth of air-stable 2D metallic 1T-CrTe2 ultrathin crystals with controlled thickness. Their long-range ferromagnetic ordering is confirmed by a robust anomalous Hall effect, which has seldom been observed in other layered 2D materials grown by chemical vapor deposition. With reducing the thickness of 1T-CrTe2 from tens of nanometers to several nanometers, the easy axis changes from in-plane to out-of-plane. Monotonic increase of Curie temperature with the thickness decreasing from ~130.0 to ~7.6 nm is observed. Theoretical calculations indicate that the weakening of the Coulomb screening in the two-dimensional limit plays a crucial role in the change of magnetic properties.

The well-defined silver (Ag) nanowires with five-twinned structure have been prepared by polyol reduction in the presence of poly(vinylpyrrolidone) (PVP K-30, 40 000). The obtained Ag nanowires are nearly monodispersed with an average diameter of 70 nm and length of 6 μm. It is confirmed from the results of thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Fourier transform Raman spectra (FT-Raman) that one monolayer of the PVP molecules might be absorbed on the surface of the Ag nanowires through Ag−O coordination. On the basis of the experimental analysis, the probable spatial conformation of the PVP molecules is supposed to be that the CH skeleton chain of the PVP is close to the surface of the Ag nanowires. The pyrrolidone ring might be tilted on the surface of the Ag nanowires through Ag:O coordination. These results may provide direct evidence for the role of the PVP molecules in the formation of the Ag nanowires.

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With strong spin−orbit coupling (SOC), ultrathin two-dimensional (2D) transitional metal chalcogenides (TMDs) are predicted to exhibit weak antilocalization (WAL) effect at low temperatures. The observation of WAL effect in VSe 2 is challenging due to the relative weak SOC and three-dimensional (3D) transport nature in thick VSe 2 . Here, we report on the observation of quasi-2D transport and WAL effect in sublimed-salt-assisted low-temperature chemical vapor deposition (CVD) grown few-layered high-quality VSe 2 nanosheets. The WAL magnitudes in magnetoconductance can be perfectly fitted by the 2D Hikami−Larkin−Nagaoka (HLN) equation in the presence of strong SOC, by which the spin−orbit scattering length l SO and phase coherence length l ϕ have been extracted. The phase coherence length l ϕ shows a power law dependence with temperature, l ϕ ∼ T −1/2 , revealing an electron−electron interaction-dominated dephasing mechanism. Such sublimed-salt-assisted growth of high-quality few-layered VSe 2 and the observation of WAL pave the way for future spintronic and valleytronic applications.

We report the chemical vapor deposition (CVD) growth, characterization, and low-temperature magnetotransport of 1T phase multilayer single-crystalline VTe2 nanoplates. The transport studies reveal that no sign of intrinsic long-range ferromagnetism but localized magnetic moments exist in the individual multilayer metallic VTe2 nanoplates. The localized moments give rise to the Kondo effect, evidenced by logarithmical increment of resistivity with decreasing temperature and negative magnetoresistance (NMR) regardless of the direction of magnetic field at temperatures below the resistivity minimum. The low-temperature resistivity upturn is well described by the Hamann equation, and the NMR at different temperatures, a manifestation of the magnetization of the localized spins, is well fitted to a Brillouin function for S = 1/2. Density functional theory calculations reveal that the localized magnetic moments mainly come from the interstitial vanadium ions in the VTe2 nanoplates. Our results will shed light on the study of magnetic properties, strong correlation, and many-body physics in two-dimensional metallic transition metal dichalcogenides.

Organic spintronic devices present one of the most appealing technologies for future spintronic devices by taking advantage of the spin degree of freedom. Conjugated polymers are attractive for the exemplified device of organic spin valves (OSVs) due to their weak spin–orbit coupling, solution-processability, low production cost, and mechanical flexibility. However, the performance of polymer SVs is a matter of debate, as the evaporated top ferromagnetic (FM) electrode will penetrate into the organic layer during a typical fabrication process, especially in the device with an organic layer thickness of nanometers. It will cause a severe problem in controllable and reproducible spin manipulations, not to mention the clarification of the spin-dependent transport mechanism. Here, a universal, simple, and low-cost method based on a transferred electrode is developed for a polymer spin valve with stable and reliable state operation. It is demonstrated in an OSV device with a vertical structure of La2/3Sr1/3MnO3 (LSMO)/P3HT/AlO x /Co/Au that this approach not only builds a damage-free interface between magnetic electrodes and an organic spacer layer but also can be generalized for other devices with delicate active layers. Furthermore, a multistate writing and reading prototype is achieved on the premise of robust and quick magnetic response. The results reveal the importance of a spinterface and effective thickness of the organic layer in fundamental spintronic research and may lead to a strong potential in future flexible, large-area, and robust organic multifunctional circuits.