Charge Trapping in Monolayer and Multilayer Epitaxial Graphene

Abstract

We have studied the carrier densitiesnof multilayer and monolayer epitaxial graphene devices over a wide range of temperaturesT. It is found that, in the high temperature regime (typicallyT≥ 200 K),ln⁡(n)shows a linear dependence of 1/T, showing activated behavior. Such results yield activation energiesΔEfor charge trapping in epitaxial graphene ranging from 196 meV to 34 meV. We find thatΔEdecreases with increasing mobility. Vacuum annealing experiments suggest that both adsorbates on EG and the SiC/graphene interface play a role in charge trapping in EG devices.

Temperature dependence of electron density and electron–electron interactions in monolayer epitaxial graphene grown on SiC

“…The T -independence of the carrier density in our system is evidence that the charge trapping model in epitaxial graphene on SiC is not applicable in the low temperature regime [39, 40]. It is also worth mentioning that at high temperatures, from Device 2 (see Figure 5 in supplementary information) the Hall slope deviates from the red solid line and we cannot simply ascribe this abrupt change to the e - e interactions.…”

“…It is also worth mentioning that at high temperatures, from Device 2 (see Figure 5 in supplementary information) the Hall slope deviates from the red solid line and we cannot simply ascribe this abrupt change to the e - e interactions. Neither can we attribute this phenomenon simply to the charge trapping effect since our data cannot be fitted to the Arrhenius-type equation [39, 40]. It is possible that in our device the carrier density does increase in the high temperature regime.…”