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Observation of the Memory Steps in Graphene at Elevated Temperatures


Many unique properties of graphene, such as extremely high carrier mobility and intrinsic thermal conductivity, chemical inertness and mechanical stiffness have attracted enormous attention. Many, although not all, unique features of this material have been understood. Practical applications of graphene in transparent electrically conductive electrodes and thermal management seem to be rather realistic. Far less clear is how to capitalize on graphene’s properties in electronic applications.

IGERT faculty and professor of Electrical Engineering and Physics Michael S. Shur at Rensselaer Polytechnic Institute, Troy, NY and his domestic and international collaborators have discovered a new electronic effect in four-terminal graphene devices (see Figure a), which they observed at elevated temperatures T > 500 K. They found that the current-voltage characteristics of graphene transistors exhibit an intriguing feature – an abrupt change of the current near zero gate bias at temperatures above 500 K. The strength of this effect, which they refer to as the memory step by analogy with the memory dips – known phenomenon in electron glasses, depends on the rate of the gate voltage sweep. The slower the sweep – the more pronounced is the step in the current. Despite differences in examined graphene transistors, the memory step always appears at Vg about 0 V. See Figure (b). The observed memory steps can be related to the slow relaxation processes in graphene. This effect can be a signature of some slow relaxation process or phase transitions in the graphene electronic system. In the vicinity of this transition, the sample is extremely sensitive to external perturbations, and therefore this effect might be very useful for electronic high temperature sensing applications and switches.

Address Goals

The discovery of a new electronic effect in four-terminal graphene devices at high temperature advances the frontiers of graphene electronics knowledge. It also has potential applications in electronic high temperature sensing applications and switches. It keeps the US in a leading position of nanoelectronics and engineering.

In the process of designing and testing of the graphene devices, the IGERT faculty and trainees learned to work together with domestic and international collaborators, and developed science and engineering skills as well as disseminated findings to society through outreach activities and professional conferences.