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Recently, under the guidance of Professor Zeng Changgan, Qi Ji and other undergraduates from Yanjici Class, School of Physics, University of Science and Technology of China, made important progress in the photoelectric regulation of graphene, using grating pressure to regulate the doping of graphene placed on the surface of semiconductors Type and carrier concentration, and achieve electronic superlattice. The research results are published in the international authoritative magazine Advanced Materials under the title of "Controlled ambipolar tuning and electronic superlattice fabrication of graphene via optical gating". Qi Ji is the first author.
The control of the carrier concentration of graphene is very important, usually achieved by electric grid voltage or chemical doping. However, the regulation of electric grid voltage requires an insulating dielectric layer, and chemical doping lacks concise and effective adjustability. Qi Ji et al found that the grating pressure can be used to control the carrier of graphene placed on the surface of a general semiconductor: Schottky electric field usually exists at the interface between semiconductor and graphene. When the incident light energy is greater than the semiconductor energy gap, the interface electric field will cause excitation The electron-hole pairs separate and drive one of the carriers to accumulate in the graphene, thereby realizing the regulation of the carrier by the grating pressure. Since graphene has only a single layer and the intrinsic carrier concentration is very low, this adjustment is very effective. By changing the light intensity, the doping type can be reversibly changed from p to n. On the other hand, the space-dependent regulation of graphene carriers can realize various novel quantum effects, such as Klein tunneling, anisotropic electrical transport, and so on. Qi Ji et al. Used a template with periodic long holes to perform spatially selective grating pressure regulation, thereby realizing the preparation of an electronic superlattice (such as p-p + superlattice). More interestingly, this p-p + electron superlattice has a strong transport anisotropy: along the direction of the superlattice, the more the number of periodic barriers, the smaller the resistance; but perpendicular to the direction of the superlattice , The resistance does not change with the number of cycles. This anisotropy may originate from the nonlinear dynamic effects of carriers at the p-p + interface. This work provides new enlightenment for exploring the novel physical properties of graphene and the development of graphene-based optoelectronic devices.
Schematic diagram of grating pressure regulation and electronic superlattice preparation
The above research work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology, the Ministry of Education and the Quantum Information and Quantum Technology Frontier Collaborative Innovation Center.
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