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The photocurrent in graphene has drawn much attention in recent years. The mechanisms of its production vary in different situations, such as at the interfaces of monolayer-bilayer junction or p-n junction. Here we demonstrate photocurrent generation in graphene-based field-effect transistors (GFETs) with a partially suspended area. Both Raman and photocurrent mapping were performed after a laser-induced...
We demonstrate a facile method to grow highly uniform monolayer graphene films on copper foils by atmospheric pressure chemical vapor deposition (APCVD). The technique in this method includes lowering flow ratio of methane/hydrogen and extending exposure time to hydrogen. All the multilayer islands will be etched away by hydrogen during this growth process, resulting in obtaining highly uniform monolayer...
In this paper, we focus on the influence of series resistance of signal line (comoprised of the sheet resistance of graphene and the contact resistance between graphene and metal) on the radio-frequency transmission property of graphene coplanar waveguide (CPW) and put forward ways to improve it. According to our research, the large series resistance (7.2 kΩ) of signal line is the main reason for...
In this paper, a 3D metal-graphene contact with different contact structures (i.e., embedded contact and edge contact) is studied using Kirchhoff model. The influences of some major factors, including metal resistivity, metal-graphene contact resistivity and sheet resistances of graphene both in the channel and under metal, on the total contact resistance are investigated. The sheet resistance of...
Graphene films, produced by chemical vapor deposition (CVD) on copper foils, generally have a lot of line-defects, such as grain boundaries and nanogaps between adjacent graphene domains. We demonstrated to identify such 1-D defects with size less than 20 nanometers using friction force microscopy (FFM). These line defects can be clearly observed in friction force images, while no height variation...
Poly(methyl methacrylate) (PMMA) is widely used for graphene transfer and device fabrication. However, it inevitably leaves a thin layer of polymer residues after acetone rinsing and leads to dramatic degradation of device performance. How to eliminate contamination and restore clean surfaces of graphene is still highly demanded. In this paper, we present a reliable and position-controllable method...
We present modeling and simulations of graphene coplanar waveguide (GCPW) under the frequency up to 50 GHz. Our simulation results show that the dimensions of GCPW greatly influence its insertion loss. In addition, different graphene layer numbers and structures of graphene-metal contact were also considered. We show that the usage of few-layer graphene and end-contact structure is able to decrease...
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