To fabricate functional electronic devices based on graphene, a support layer must be used to transfer the graphene from the growth substrate to the target substrate. The most widely used graphene transfer support layer is polymethyl methacrylate (PMMA), however, the resulting polymer contamination and wrinkling problems reduce the carrier mobility of graphene. Although support layers made of other polymers and organic molecules have been tried, neither problem has been completely solved.
Professor Jing Kong and others from the Massachusetts Institute of Technology proposed the use of paraffin to transfer graphene, which solved the problem of contamination and wrinkling of the support layer in graphene transfer. This technology utilizes the low chemical reactivity and high thermal expansion coefficient of paraffin, so that the paraffin of the support layer is thermally expanded, thereby eliminating the wrinkles of graphene. paraffin wax suppliers Density functional theory calculations confirm that paraffin has a low graphene adsorption energy, which can effectively reduce the pollution of the support layer. Meanwhile, atomic force microscopy and Raman confirmed that the paraffin-transferred graphene has a smooth morphology and near-intrinsic doping and strain levels. Field-effect transistors based on paraffin-transferred graphene exhibit electrical properties close to that of intrinsic graphene, and the electron mobility is about four times higher than that of PMMA-transferred graphene.
Compared with the complex chemical structure of PMMA, paraffin has only simple carbon and hydrogen chains, stable chemical properties, and low reactivity; at the same time, it has a high thermal expansion coefficient. Field effect transistors constructed based on paraffin-transferred graphene have a voltage corresponding to the Dirac point close to zero and high carrier mobility. The transfer technique also opens up new avenues for obtaining other wrinkle-free, intrinsic 2D materials.
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