Despite its extremely weak intrinsic spin-orbit coupling (SOC), graphene has been shown to acquire considerable SOC by proximity coupling with exfoliated transition metal dichalcogenides (TMDs). Here we demonstrate strong induced Rashba SOC in graphene that is proximity coupled to a monolayer TMD film, MoS 2 or WSe 2 , grown by chemical vapor deposition with drastically different Fermi level positions. Graphene/TMD heterostructures are fabricated with a pickup-transfer technique utilizing hexagonal boron nitride, which serves as a flat template to promote intimate contact and therefore a strong interfacial interaction between TMD and graphene as evidenced by quenching of the TMD photoluminescence. We observe strong induced graphene SOC that manifests itself in a pronounced weak anti-localization (WAL) effect in the graphene magnetoconductance. The spin relaxation rate extracted from the WAL analysis varies linearly with the momentum scattering time and is independent of the carrier type. This indicates a dominantly Dyakonov-Perel spin relaxation mechanism caused by the induced Rashba SOC. Our analysis yields a Rashba SOC energy of ~1.5 meV in graphene/WSe 2 and ~0.9 meV in graphene/MoS 2 , respectively. The nearly electron-hole symmetric nature of the induced Rashba SOC provides a clue to possible underlying SOC mechanisms.

Monolayer transition metal dichalcogenides are uniquely-qualified materials for photonics because they combine well-defined tunable direct band gaps and self-passivated surfaces without dangling bonds. However, the atomic thickness of these two-dimensional (2D) materials results in low photo absorption limiting the achievable photo luminescence intensity. Such emission can, in principle, be enhanced via nanoscale antennae resulting in; a) an increased absorption cross-section enhancing pump efficiency, b) an acceleration of the internal emission rate via the Purcell factor mainly by reducing the antenna's optical mode volume beyond the diffraction limit, and c) improved impedance matching of the emitter dipole to the free-space wavelength.Plasmonic dimer antennae show orders of magnitude hot-spot field enhancements when an emitter is positioned exactly at the mid-gap. However, a 2D material cannot be grown, or easily transferred, to reside in mid-gap of the metallic dimer cavity. In addition, a spacer layer between the cavity and the emissive material is required to avoid non-radiative recombination channels.Using both computational and experimental methods, in this work we show that the emission enhancement from a 2D emitter-monomer antenna cavity system rivals that of dimers at much reduced lithographic effort. We rationalize this finding by showing that the emission enhancement in dimer antennae does not specifically originate from the gap of the dimer cavity, but is an average effect originating from the effective cavity crosssection taken below each optical cavity where the emitting 2D film is located. In particular, we test an array of different dimer and monomer antenna geometries and observe a representative ~300% higher emission for both monomer and dimer cavities as compared to intrinsic emission of Chemical Vapor Deposition (CVD)-synthesized WS 2 flakes. Observed enhanced light emission from these 3 atomically thin flakes together with the lithographic control of plasmonic antennae on them opens opportunities for engineering light-matter interaction in 2D systems in a test-bed comparable fashion, enabling bright and large-scale 2D opto-electronics.

In this work, the fabrication of WO3∕W nanocrystals for nonvolatile memory devices has been achieved via rapid thermal oxidation of tungsten silicide. Amorphous Si and WSix (x=2.7) layers were deposited onto the tunneling oxide and sequentially oxidized to form well-shaped WO3∕W nanocrystals. The mean size of WO3∕W nanocrystals is ∼8.4nm, while density is ∼1.57×1011cm−2. Moreover, the nonvolatile memory device for WO3∕W nanocrystals exhibits ∼0.53V threshold voltage shift under 1V∕(−5V) operation. The sample without capping a-Si layer was also fabricated for comparison. By material analyses, reasonable formation mechanisms are proposed in this letter.

A supercritical CO2 (SCCO2) fluid technique is proposed to improve electrical characteristics for W nanocrystal nonvolatile memory devices, since the thickness and quality of tunnel oxide are critical issues for the fabrication of nonvolatile memory devices. After SCCO2 treatments, C-V curves are restored to normal, as well as the leakage current of W nanocrystal memory devices are reduced significantly. It reveals that W nanocrystal memory devices could be formed with shorter oxidation time, moreover, dangling bonds and trapping states initially created within an incomplete oxidized film will be efficiently repaired after SCCO2 treatment.

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