Graphene: a membrane with steadily improving charge and spin transport properties
Bernd Beschoten (RWTH Aachen)

Graphene research has prospered impressively in the past years, and promising applications such as high frequency transistors, THz detectors, magnetic field sensors, flexible optoelectronics, and spintronics applications are waiting for a scalable and cost efficient fabrication technology to produce high-quality, i.e. high-mobility graphene. Although significant progress has been made in chemical vapor deposition (CVD) of "synthetic" graphene on copper foils, typical charge carrier mobilities are significantly lower than what is achieved using exfoliated "natural" graphene. We show that the quality of CVD-grown graphene depends critically on the used transfer process, where the true membrane property of graphene - placing this material right at the crossover from "soft" to "hard" matter - plays a crucial role. We report on an advanced transfer technique that allows making devices with carrier mobilities up to three million cm2/(Vs) thus rivaling exfoliated "natural" graphene. This brings novel electron-optic devices into reach. Furthermore, we demonstrate that dry transfer techniques are also the key to push the spin transport properties of graphene beyond the 10 ns benchmark of the spin lifetime at room temperature. This is of high technological interest as it marks the threshold at which manipulation of spins with electrical high frequency technology becomes feasible.