Reversible control of interface-water induced carrier density in graphene-on-SiO₂ by thermal cycling under gate-voltage

A reversible handle on graphene carrier density, other than the gate electric field, is desirable for memory applications of graphene. Our experiments show that the commonly observed carrier density hysteresis in graphene on SiO$_2$ due to interface water/oxygen vanishes at temperatures below 250 K. The state of these species, which affects the graphene carrier density, at low temperatures can be reversibly controlled by thermal cycling to room temperature at different gate voltages. Further, devices prepared with relatively dry interface, and thus showing negligible hysteresis at room temperature, show a marked increase in hysteresis on heating above room temperature. Thus thermal-cycling, to high temperatures and under gate-voltage, provides a reversible handle on carrier density. These results are discussed in terms of temperature and interface-water density dependence of redox-reaction kinetics.