Research Of Measurement Methods On The Properties Of Graphene Thin Film In The Microwave Wave Frequency Range

There is a growing interest in microwave devices to research the graphene. As a new nano-electronic materials, the graphene has perspective application on the RF components. The microwave dielectric parameters of graphene is the basis of microwave circuit research, it’s very important for the development of graphene microwave circuit to study the test method. Because of the graphene has nanoscale dimensions and properties of metal-semiconductor, there are some problem on the test method of the traditional dielectric parameters, such as the low sensitivity and large measurement errors, even failure. As a result, it is limited to research the equivalent circuit model of the transmission line on a small area graphene, which is made by mechanical stripping method. However, research on dielectric parameters of a large area graphene by chemical vapor deposition(CVD) is not yet reported, which greatly limits the development of graphene circuit design.In this paper, we select the method of microwave transmission measurement for the characteristics of graphene to adapt to the wide frequency and high loss dielectric films, contrasting the advantages and disadvantages of various microwave measurement methods about thin film by theoretical analysis. In the frequency range of 6GHz ~ 40 GHz, we measure the dielectric parameters of graphene films in the structure of multilayer dielectric coplanar waveguide transmission line, which made by chemical vapor deposition(CVD). The use of vector network analyzers(VNA) and microwave probes to directly measure the S parameters of multilayer dielectric coplanar waveguide, and extract the complex permittivity of graphene from S parameter by the transmission line theory. In this paper, meanwhile, we establish the errors model of vector network analyzer(VNA) and the method of calibration, In order to improve the measurement accuracy and the measurement frequency range, we use the TRL calibration method which base on 10 errors model.In this paper, the test sample is made by nano-fabrication process. We establish the multilayer dielectric model and extract the microwave dielectric parameters of graphene directly from the test results. Finally, we compare the theoretical analysis with the experimental measurements to verify the correctness of the theory and reliability of the test method. The method can measure the dielectric parameters of large-area graphene that lay the foundation for the design of graphene circuit.