Chemical substitution during growth is a well-established method to manipulate electronic states of quantum materials, and leads to rich spectra of phase diagrams in cuprate and iron-based superconductors. Here we report a novel and generic strategy to achieve nonvolatile electron doping in series of (i.e. 11 and 122 structures) Fe-based superconductors by ionic liquid gating induced protonation at room temperature. Accumulation of protons in bulk compounds induces superconductivity in the parent compounds, and enhances the T c largely in some superconducting ones. Furthermore, the existence of proton in the lattice enables the first proton nuclear magnetic resonance (NMR) study to probe directly superconductivity. Using FeS as a model system, our NMR study reveals an emergent high-T c phase with no coherence peak which is hard to measure by NMR with other isotopes. This novel electric-field-induced proton evolution opens up an avenue for manipulation of competing electronic states (e.g. Mott insulators), and may provide an innovative way for a broad perspective of NMR measurements with greatly enhanced detecting resolution.

Two-dimensional materials (2DMs) with extraordinary electronic and optical properties have attracted great interest in optoelectronic applications. Due to their atomically thin feature, 2DM-based devices are generally sensitive to oxygen and moisture in ambient air, and thus, practical application of durable 2DMbased devices remains challenging. Here, we report a novel strategy to directly synthesize amorphous BN film on various 2DMs and field-effect transistor (FET) devices at low temperatures by conventional chemical vapor deposition. The wafer-scale BN film with controllable thickness serves as a passivation and heat dissipation layer, further improving the long-term stability, the resistance to laser irradiation, and the antioxidation performance of the underneath 2DMs. In particular, the BN capping layer could be deposited directly on a WSe 2 FET at low temperature to achieve a clean and conformal interface. The high performance of the BNcapped WSe 2 device is realized with suppressed current fluctuations and 10-fold enhanced carrier mobility. The transfer-free amorphous BN synthesis technique is simple and applicable to various 2DMs grown on arbitrary substrates, which shows great potential for applications in future two-dimensional electronics.

No abstract

No abstract

No abstract