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In this paper, a Conductive Atomic Force Microscope was used to measure the current distribution image of monolayer graphene oxide (GO) and I/V curves of different types of points in current distribution. Graphene oxide (GO) was prepared by a modified Hummer’s method and deposited on highly oriented pyrolytic graphite. We gradually increase the voltage range and analyze the effect of different voltages on improving the local conductivity of graphene oxide. It has been found that there are several critical voltages, such as 0.8 V, 1.5 V, 2.2 V, and 3.2 V. There is no current when the voltage is lower than 0.8 V; if the voltage is 1.5–2.1 V, the conductivity of GO can be slightly improved, but if not, it will significantly change the structure of graphene oxide; if the voltage is 2.2–3.1 V, the conductivity of GO can be greatly improved, but it still exhibits semiconductor properties; when the voltage increases to 3.2 V, the local conductivity of GO changes, showing metallicity. It was concluded that the strong electric field strength caused by voltage destroys the bond between oxygen-containing functional groups and the graphene oxide skeleton, which is very advantageous for studying the conductivity of GO.

We studied the structures and electronic properties of Janus transition-metal dichalcogenide monolayers MXY (M = Mo, W; X ≠ Y = S, Se, Te) by first-principles calculations. The results of the electronic band structures and the density of states reveal that all of the MXY monolayers show semiconducting characteristics. Particular attention has been focused on the bandgap engineering by applying in-plane biaxial compressive and tensile strain. It is observed that the bandgap values of the MXY monolayers decrease with the increase of strain degree under the tension and compression biaxial strain, and a semiconductor-to-metal transition can be undergone at a critical value of strain. The possibility of the tunable energy gap over a wide range makes MXY monolayers potential candidates for nanoelectronics and optoelectronics.

Functionalization of MoS2 sheet (monolayer and bilayer) by the adsorption of transition metal Fe adatom to its surface and interlayer has been investigated computationally using first-principles calculations based on the density functional theory. We found that the systems with absorption of Fe adatoms on the surfaces of both monolayer and bilayer MoS2 sheets are still semiconductors, without spin polarization at the Fermi level. However, for the system with absorption of Fe adatom in the interlayer of bilayer MoS2 sheet, its electronic structure exhibits half-metal behavior, with 100% spin polarization at the Femi level, which provides a promising material for spintronic devices.

We report the electrostatic properties of few-layer Bi2Te3 and Bi2Se3 nanoplates (NPs) grown on 300 nm SiO2/Si substrate. Electrons and holes are locally injected in Bi2Te3 and Bi2Se3 nanoplates by the apex of an atomic force microscope tip. Both carriers are delocalized uniformly over the whole nanoplate. The electrostatic property of topological insulator Bi2Te3 and Bi2Se3 nanoplates after charge injection is characterized by Kelvin probe force microscopy under ambient environment and exhibits an ambipolar surface potential behavior. These results provide insight into the electronic properties of topological insulators at the nanometer scale.