Graphene-based heterostructure is one of the most attractive topics in physics and material sciences due to its intriguing properties and applications. We report the one-step fabrication of a novel graphene/Mo 2 C heterostructure by using chemical vapor deposition (CVD). The composition and structure of the heterostructure are characterized through energydispersive spectrometer, transmission electron microscope, and Raman spectrum. The growth rule analysis of the results shows the flow rate of methane is a main factor in preparing the graphene/Mo 2 C heterostructure. A schematic diagram of the growth process is also established. Transport measurements are performed to study the superconductivity of the heterostructure which has potential applications in superconducting devices.

Based on the support of RS and GIS technology, this paper analyzes the spatial and temporal variation characteristics and driving forces of land use in the Yanhe River Basin through the processing and interpretation of remote sensing images in different periods from 1980 to 2015 and the methods of the land use transfer matrix and dynamic attitude. The results show that cropland, grassland, and forest land are the three types of land use with the most obvious changes, while urban land and water body have relatively small changes in the Yanhe River Basin. The transfer between cropland, forest land, and grassland and urban land is very obvious, among which the conversion rate of cropland is the highest. During the 15 years from 2000 to 2015, the land use types of the Yanhe River Basin changed by 13.17%, with an average annual growth rate of 0.88%. The implementation of ecological restoration and governance policy is the direct driving force of land use change in the Yanhe River Basin. The results obtained in this study can provide reference basis for land use planning and management and land use structure optimization in the Yanhe River Basin in the future.

Oxygen can passivate Cu surface active sites when graphene nucleates. Thus, the nucleation density is decreased. The CuO/Cu substrate was chosen for graphene domain synthesis in our study. The results indicate that the CuO/Cu substrate is beneficial for large-scale, single-crystal graphene domain synthesis. Graphene grown on the CuO/Cu substrate exhibits fewer nucleation sites than on Cu foils, suggesting that graphene follows an oxygen-dominating growth. Hydrogen treatment via a heating process could weaken the surface oxygen's role in limiting graphene nucleation under the competition of hydrogen and oxygen and could transfer the synthesis of graphene into a hydrogen-dominating growth. However, the competition only exists during the chemical vapor deposition heating process. For non-hydrogen heated samples, oxygen-dominating growth is experienced even though the samples are annealed in hydrogen for a long time after the heating process. With the temperature increases, the role of hydrogen gradually decreases. The balance of hydrogen and oxygen is adjusted by introducing hydrogen gas at a different heating temperatures. The oxygen concentration on the substrate surface is believed to determine the reactions mechanisms based on the secondary ion mass spectrometry test results. This study provides a new method for the controllable synthesis of graphene nucleation during a heating process.