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Strain relaxation in different shapes of single crystal graphene grown by chemical vapor deposition on copper

https://doi.org/10.1016/j.carbon.2020.07.025

Nanayakkara, Tharanga R.; Wijewardena, U. Kushan; Withanage, Sajith M.; Kriisa, Annika; Samaraweera, Rasanga L.; Mani, Ramesh G. (July 2020, Carbon)

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The role of surface morphology on nucleation density limitation during the CVD growth of graphene and the factors influencing graphene wrinkle formation

https://doi.org/10.1557/adv.2020.73

Withanage, Sajith; Nanayakkara, Tharanga; Wijewardena, U. Kushan; Kriisa, Annika; Mani, R. G. (January 2019, MRS Advances)

ABSTRACT CVD graphene growth typically uses commercially available cold-rolled copper foils, which includes a rich topography with scratches, dents, pits, and peaks. The graphene grown on this topography, even after annealing the foil, tends to include and reflect these topographic features. Further, the transfer of such CVD graphene to a flat substrate using a polymer transfer method also introduces wrinkles. Here, we examine an electropolishing technique for reducing native foil defects, characterize the resulting foil surface, grow single-crystal graphene on the polished foil, and examine the quality of the graphene for such defects.
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Effects of Long-Time Current Annealing to the Hysteresis in CVD Graphene on SiO ₂

https://doi.org/10.1557/adv.2019.366

Wijewardena, U. Kushan; Nanayakkara, Tharanga; Samaraweera, Rasanga; Withanage, Sajith; Kriisa, Annika; Mani, Ramesh G. (January 2019, MRS Advances)

ABSTRACT Graphene specimens produced by chemical vapor deposition usually show p-type characteristics and significant hysteresis in ambient conditions. Among many methods, current annealing appears to be a better way of cleaning the sample due to the possibility of in-situ annealing in the measurement setup. However, long-time current annealing could increase defects in the underlying substrate. Studying the hysteresis with different anneal currents in a graphene device is, therefore, a topic of interest. In this experimental work, we investigate electron/hole transport in a graphene sample in the form of a Hall bar device with a back gate, where the graphene was prepared using chemical vapor deposition on copper foils. We study the hysteresis before and after current annealing the sample by cooling down to a temperature of 35 Kfrom room temperature with a back-gate bias in a closed cycle refrigerator.
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