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Reducing the contact resistance without degrading the mobility property is crucial to achieve high-performance graphene field effect transistors. Also, the idea of modifying the graphene surface by etching away the deposited metal provides a new angle to achieve this goal. We exploit this idea by providing a new process method which reduces the contact resistance from 597 Ω·μm to sub 200 Ω·μm while no degradation of mobility is observed in the devices. This simple process method avoids the drawbacks of uncontrollability, ineffectiveness, and trade-off with mobility which often exist in the previously proposed methods. [ABSTRACT FROM AUTHOR]

Grain boundary activity in nanocrystalline Al under an indenter is studied by using a multiscale method. It is found that grain boundaries and twin boundaries can be transformed into each other by emitting and absorbing dislocations. The transition processes might result in grain coarsening and refinement events. Dislocation reflection generated by a piece of stable grain boundary is also observed, because of the complex local atomic structure within the nanocrystalline Al. This implies that nanocrystalline metals might improve their internal structural stability with the help of some special local grain boundaries. [ABSTRACT FROM AUTHOR]