Recently, the Institute of Microelectronics of Chinese Academy of Sciences has made an overall breakthrough in the development of graphene materials and devices. The team led by Jin Zhi, a researcher in the Microwave Devices and Integrated Circuits Research Laboratory (Microelectronics Institute of Microelectronics) under the support of scientific research projects of the State and Chinese Academy of Sciences, conducted in-depth and systematic analysis of graphene material growth, transfer, and preparation of graphene RF devices. The research has produced a graphene radio frequency device with extremely high oscillation frequency and achieved a series of important results.
As a new two-dimensional carbon material, graphene has broad application prospects in the field of microelectronics due to its excellent electrical and optical properties and stable chemical properties. Chemical vapor deposition is one of the important ways to obtain high-quality graphene, but the transfer of graphene from the metal surface to the target substrate is a “bottleneck†restricting the promotion of this method. The four-compartment research team creatively used agarose gel as a solid electrolyte to achieve efficient and green transfer of graphene using electrochemical methods. The transfer method can be extended to the preparation of large-scale graphene films, providing a feasible route for the large-scale application of graphene.
The metal substrate used for growing graphene will form an orderly topography on the surface during the preparation process, and this structure will lead to a large number of orderly arranged wrinkles in the transferred graphene film. The four-compartment research team has studied the effect of wrinkles on the carrier transport in graphene by preparing a graphene RF device with special structure. It was found that this orderly wrinkling could cause the carrier transport in graphene to have different Anisotropic characteristics: The mobility of carriers parallel to the direction of the fold is significantly higher than in the vertical direction. This discovery provides an important reference for the preparation of high performance graphene RF devices.
During the preparation of graphene RF devices, the existing gate dielectric preparation methods have certain defects in the process controllability and device performance. The four-compartment research team used a spin coating method to form a BCB film on the surface of graphene, and used this as a seed layer for the deposition of an alumina dielectric layer. The method not only has excellent process controllability, but also avoids the adverse effect on graphene performance due to the special chemical structure of BCB, and realizes the preparation of high-performance graphene RF devices.
The contact resistance between the graphene and the metal electrode affects the gate control of the graphene RF device, thereby adversely affecting the frequency characteristics of the device. As an extension of traditional thin-film material research methods, the contact between graphene and metal is currently characterized and measured by the TLM method. The four-compartment research team found that there is a big difference between the two by measuring the sheet resistance of the graphene contact and non-contact material. Further theoretical analysis shows that the difference in sheet resistance in different regions of graphene leads to a large deviation between the contact resistance and the actual value obtained by the traditional TLM method. This finding is important for improving test methods and optimizing the performance of graphene RF devices. value.
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