Despite the various techniques developed for the transfer of large area graphene grown by chemical vapor deposition (CVD), the conventional PMMA transferring technique has been widely applied in laboratories due to its convenience and economical cost. However, the complete removal of PMMA on graphene surface has become a troublesome, and the PMMA residue could degrade the properties of graphene significantly. We report here a facile water assisted technique to directly peel off the PMMA layer over centimeter-sized CVD graphene film for the first time. No organic solvents are involved in the whole transfer process. The transferred graphene film is clean and intact over large area because of the cooperative effect of the capillary force and the van der Waals force which facilitates the conformal contact between graphene film and the substrate. Various types of graphene samples (i.e. monolayer, multilayer, and incomplete domains) can be easily transferred to diverse substrates including silicon wafer, sapphire, and quartz with good integrity. The transferred graphene film is of high cleanliness, and the graphene transistors show higher carrier mobility and lower level of p-type doping comparing to the conventional wet transfer technique.

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.

Two-dimensional (2D) GaN exhibits wide bandgap, high quantum efficiency, and ultralow thermal conductivity, making it a promising candidate for optoelectronic and thermoelectric applications. In this study, we synthesize ultrathin 2D...

Spin injection, spin diffusion, and spin detection are investigated in Co/Ag/Co lateral spin valves at room temperature. Clear spin accumulation signals are detected by the non-local measurement. By fitting the results to the one-dimensional diffusion equation, ∼ 8.6% spin polarization of the Co/Ag interface and ∼ 180 nm spin diffusion length in Ag are obtained. Thermal treatment results show that the spin accumulation signal drastically decreases after 100 • C annealing, and disappears under 200 • C annealing. Our results demonstrate that, compared to the spin diffusion length, the decrease and the disappearance of the spin accumulation signal are mainly dominated by the variation of the interfacial spin polarization of the Co/Ag interface.

No abstract