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Graphene Based Radio Frequency Electronics

Final Report Summary - GRAPHENERF (Graphene Based Radio Frequency Electronics)

The specific aim of the present project is to initiate a research afford in collaboration with other European scientist to develop graphene based high performance thin film transistors (TFT) for radio frequency (RF) electronics. High performance TFTs operating at radio frequencies are of considerable interest in the area of thin film electronics. Amorphous silicon and organic semiconductors are widely used materials for recent designs. Due to the very limited electronic performance of these materials, thin film electronic circuits working at ultrahigh frequency range still remain as a technological challenge. Thus, new types of high performance semiconducting materials are of great interest for the recent research in this area. Extraordinary electronic properties together with the ability to be printed on large scales make graphene a promising candidate for these types of applications. The long term goal is to develop a new graphene based technology for high frequency electronic applications.
The project have five main sections, (1) synthesis of high quality, large area graphene, (2) developing transfer printing process for graphene, (3) fabrication of graphene transistors for high frequency applications, (4), developing analytical models to understand the working principle of graphene and nanotube transistors and (5) searching for new applications of graphene in the field of high frequency electronics.
In the first period of the project we worked on building a chemical vapor deposition system for graphene synthesis. We developed growth processes for large scale high quality graphene. Now, we can synthesize 20cmx20cm size high quality graphene on copper foils. In the second part of the project we developed large scale transfer printing processes using roll-to-roll lamination method. We were able to transfer large area high quality graphene on flexible substrates. In the third section we fabricated graphene field effect transistors operating in the high frequency regime. The contact resistance associated with metal-graphene interface is the main limiting factor for the device performance. We developed rapid thermal annealing procedure to improve the contact resistance of graphene transistors. In fourth section of the project, we worked on developing analytical models to understand the limiting physical mechanism behind the graphene transistors. We developed self consistent models for charge transport in graphene transistors. We found that scattering mechanisms induced by charged impurities are the main limiting factor of the graphene transistors. The final section of the project deals with new application of graphene in the field of high frequency electronics. We discovered new applications including graphene based radar absorbing surfaces and optoelectronic devices.

The project help the researcher setting up an independent research group at Bilkent University and his integration with the researchers in Europe. Project resulted in 19 direct journal publications. Moreover, researcher supervised four M.S. students, 4 PhD student and 2 postdoc during the project.