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Large polymer residues introduced by the graphene transfer process is still a major obstacle limiting the integration of chemical vapor deposition (CVD)-grown graphene into next-generation electronic and photoelectronic devices. Here we use cera alba, a natural and environmental-friendly material that derives from honeycomb, as the supporting layer for ultraclean graphene transfer. The transferred graphene has a low surface roughness with a surface height fluctuation within 5 nm and an only 80.08% average sheet resistance of the polymethyl methacrylate (PMMA)-transferred graphene. Further, the ultraclean graphene is used as electrodes for the PbI

Understanding the microscopic mechanisms for the nucleation and growth of two-dimensional molybdenum diselenide (2D MoSe

In-plane two-dimensional (2D) heterostructures have been attracting public attention due to their distinctive properties. However, the pristine materials that can form in-plane heterostructures are reported only for graphene, hexagonal BN, transition-metal dichalcogenides. It will be of great significance to explore more suitable 2D materials for constructing such ingenious heterostructures. Here, we demonstrate two types of novel seamless in-plane heterostructures combined by pristine Sb and Bi monolayers by means of first-principle approach based on density functional theory. Our results indicate that external strain can serve as an effective strategy for bandgap engineering, and the transition from semiconductor to metal occurs when a compressive strain of −8% is applied. In addition, the designed heterostructures possess direct band gaps with high carrier mobility (~4000 cm2 V−1 s−1). And the mobility of electrons and holes have huge disparity along the direction perpendicular to the interface of Sb/Bi in-plane heterostructures. It is favorable for carriers to separate spatially. Finally, we find that the band edge positions of Sb/Bi in-plane heterostructures can meet the reduction potential of hydrogen generation in photocatalysis. Our results not only offer alternative materials to construct versatile in-plane heterostructures, but also highlight the applications of 2D in-plane heterostructures in diverse nanodevices and photocatalysis.

In a previous paper, the model of a floating top segment was proposed and used successfully to calculate the field enhancement factor as well as the field distribution on the top surface for a single carbon nanotube (CNT). In this paper, the model is extended to a CNT array. A set of modified linear charge equations has been derived for the CNT array using an approximation of multipole potential expansion. Fictitious charges inside a specific segment can be solved from these equations to calculate the field around the tips. Some numerical calculations of the field enhancement factor have been carried out, quantitatively accounting for the reduction of the factor with decreasing intertube distance. The relative field strength distribution on the top hemisphere of a CNT array is calculated too; it is observed to be close to that of a single CNT. Using the Fowler-Nordheim formula, the field emission intensity of a CNT array is maximized with varying intertube distance. The resulting optimum intertube distance to height ratio decreases gradually with increasing height to radius ratio, and is close to 2 only for height to radius ratio around 3 × 10(2).