Effect of vacuum thermal annealing to encapsulated graphene field effect transistors

Konstantinos Alexandrou, Filippos Farmakis, Alexandros Arapis, Nikolaos Georgoulas, Yufeng Hao, James Hone and Ioannis Kymissis
2016. J. Vac. Sci. Technol. B 34(4), Jul/Aug 2016. doi: 10.1116/1.4952409

Abstract: Water vapor barriers used for graphene encapsulation can both exclude water from the environmentand trap water in the device, preventing annealing from improving device performance. In this paper,the authors investigate the effects of vacuum annealing on encapsulated single layer graphene fieldeffect transistors (SLG-FETs). The stability of GFETs is monitored for a period of up to six months,and different annealing times and atmospheres are tested to recover lost electronic performance.Fabricated encapsulated devices based on a parylene-C/aluminum passivation layers offer increasedstability over exposed back-gated devices, but still suffer from a significant Dirac point shift overextended air exposure. Our results show that GFETs subjected to varying annealing times exhibitsimilar initial behavior, characterized by a substantial reduction of their doping profile due to desorption of oxygen/water molecules, but drastically different long term stability. This suggests that moderatevacuum annealing can dehydrate even encapsulated devices, whereas extended annealing timescan damage the encapsulation layer.

Keywords: single-layer graphene, field-effect transistor, encapsulation