Electroburning process of few-layer graphene constrictions

Few-layer graphene (FLG) has been used to generate nanogap electrodes for single-molecule devices and nanosensors by the feedback controlled electroburning method. However, the evolution of the FLG constrictions during electroburning has not been well investigated yet. In this work, the morphology of the FLG constrictions is systematically characterized by atomic force microscopy during the electroburning process. The change of the constriction thickness suggests that the electroburning occurs from the periphery to the center and from the top to the bottom. Interestingly, the electroburning process terminates with a straight edge and an opposite meniscus-shaped edge. The morphology evolution and the ended shape of FLG constrictions can be attributed to the temperature distributions during the electroburning process and the local reaction activity. The COMSOL simulations indicate non-uniform local electro-thermal fields in the device, supporting our explanation. This work provides insights into the detailed process of electroburning in FLG constrictions.