2021-06-10

Our scientists have made new progress in graphene research

By yqqlm yqqlm

Graphene’s unique structure contains rich and novel physics, which not only provides an important research platform for basic science, but also , Optoelectronics, flexible devices and other fields show broad application prospects. In order to give full play to the excellent properties of graphene and realize its industrial production and application, it is necessary to find a suitable material preparation method so that the prepared graphene can simultaneously meet the conditions of large area, high quality, and compatibility with existing silicon processes. Up to now, large-area, high-quality graphene single crystals are usually obtained by epitaxial growth on the surface of transition metals, but the subsequent complex transfer process usually causes degradation of graphene quality and interface pollution, which hinders graphene’s electronic growth. Device applications.

In recent years, academician of the Chinese Academy of Sciences, researcher of the Key Laboratory of Nanophysics and Devices at the Institute of Physics of the Chinese Academy of Sciences/Beijing National Research Center for Condensed Matter PhysicsGao Hongjun led the team to carry out research and exploration in the preparation, physical property control and application of graphene and graphene-like two-dimensional atomic crystal materials, and achieved a series of research results. In the early research work, the researchers found that the graphene epitaxially grown on the transition metal surface has the advantages of large area, high quality, continuous, and controllable layer number; further developed the heterogeneous element intercalation technology based on this system, The use of this technology can effectively avoid the complex graphene transfer process, so that large-area, high-quality graphene single crystals can be non-destructively placed in heterogeneous element intercalationAbove the base. Subsequently, the researchers revealed the universal mechanism of the non-destructive intercalation of graphene; using this intercalation technology, the construction of a graphene/silylene heterojunction that exists stably in the air and the regulation of the electronic structure of graphene have been realized.

On the basis of the above research, the research team’s postdoctoral fellow Guo Hui, doctoral student Wang Xueyan, and deputy chief engineer Huang Li, etc. through continuous efforts, achieved the epitaxial high-quality graphene on the metal surface Silica insulating intercalation layer, and in-situ constructed graphene electronic devices. The researchers realized the epitaxial growth of centimeter-sized, single-crystal graphene on the surface of Ru(0001); on this basis, they developed a step-by-step intercalation technique. By inserting two elements of silicon and oxygen on the same sample, the graphene The silicon dioxide film grows at the interface with the Ru substrate; as the amount of silicon and oxygen intercalation increases, the silicon dioxide at the interface gradually becomes thicker, and its structure changes from a crystalline state to an amorphous state; When the intercalation film reaches a certain thickness, the graphene and the metal substrate are insulated; using the graphene material on the silica intercalation substrate, the preparation of in-situ non-transferred epitaxial graphene devices can be realized. In the experiment, firstly through cross-sectional scanning transmission electron microscope research, proved the thin layer of crystalline silica Double-layer structure, further combined with scanning tunneling microscope and Raman spectroscopy research shows that silica intercalation After that, graphene still maintains large-area continuous and high-quality properties; as the amount of silicon and oxygen intercalation increases, the thickness of silicon dioxide at the image display interface of the scanning transmission electron microscope can reach 1.8 nanometers; vertical transport tests and theoretical calculations show , The thick layer of amorphous silicon dioxide (1.8 nanometers) intercalation greatly restricts the electron transport process from graphene to the metal Ru substrate, and realizes the electrical near-insulation between the graphene and the metal Ru substrate; based on 1.8 Nano-silica intercalated samples, graphene electronic devices were prepared in situ, and through the transport test under low temperature and strong magnetic field, the integer quantum Hall effect and weak inverse localization of epitaxial graphene were observed. phenomenon. These phenomena are derived from the intrinsic properties of graphenetwo-dimensional electron gas, which further proves that the 1.8-nanometer non- The intercalation of crystalline silica does not destroy the large-area and high-quality properties of graphene, and it effectively isolates the graphene from the metal substrate.Coupling.

This research provides a new method for preparing large-area, high-quality graphene single crystals fused with silicon-based technology, and provides a basis for the application research of graphene materials and devices. (Reporter Zhan Yuan, Correspondent Guo Hui)

Source:Guangming Daily