Jun 13, 2013
Understanding non-ohmic behaviour in hydrogenated graphene
In a recent study, scientists from National Taiwan University (NTU), National Cheng Kung University (NCKU) and the University of Cambridge, have investigated the electrical behaviour of mono-layered graphene exposed briefly to hydrogen plasma (~6 s). Such partially hydrogenated graphane is highly disordered and shows localization effects. In other words, hopping behavior – where charge jumps from one localized state to the other – can be observed. In contrast to pristine graphene, the current-voltage I(V) characteristics are highly non-linear and show strong temperature (T) dependences.
Conduction through the device is strongly suppressed in the low-bias regime, reminiscent of gap formation. At a sufficiently high bias, charge transport is completely determined by the applied high electric field, independent of T. Such an effect could be beneficial for applications in T-insensitive devices such as low-T amplifiers stable over a range of T, and low-power devices.
By fitting their results to theoretical models, the researchers show that charge-charge interactions are dominant in the hydrogenated material. Applying a magnetic field perpendicular to the plane of graphene can decrease the resistance of the device. A high electric field can also drastically reduce the resistance of the device. Therefore delocalization of carriers can be achieved simply by applying either an electric field or a magnetic field.
Full details can be found in the journal Nanotechnology.
About the author
This study was conducted by researchers from NTU and NCKU in Taiwan, and the University of Cambridge, UK. The teams are funded partly by the Research Co-operation Initiative. Shun-Tsung Lo and Chiashain Chuang are PhD students in the Department of Physics at NTU. Reuben Puddy is currently a PhD student under the supervision of Prof. Charles Smith who is a team leader in the Semiconductor Physics Group, Cavendish Laboratory, University of Cambridge. Prof. Smith is interested in low-temperature scanning gate microscopy and high-frequency measurements of nanostructures. Prof. Tse-Ming Chen works in the Department of Physics at NCKU and is particularly interested in one-dimensional charge transport. Prof. Chi-Te Liang is group leader in the Department of Physics at NTU. He is very interested in quantum phase transitions and transport in two-dimensional systems.