Epitaxial graphene grown on SiC (0001) showed significant changes in electrical resistance upon exposure to polar protic and polar aprotic vapors in the ambient atmosphere. The dipole moment of these chemicals was found to have a strong impact on the magnitude of the sensor response, which increases with increasing dipole moment. Using the combination of low-frequency noise and Hall measurements, we demonstrate that the chemical sensing mechanism in epitaxial graphene is based on fluctuations of the charge carrier density induced by vapor molecules adsorbed on the surface of the graphene.

The electrical characteristics of oxygen functionalized epitaxial graphene and Ti/Au metal contact interfaces were systematically investigated as a function of temperature. As the temperature was increased from 300 K to 673 K, the contact resistance and the sheet resistance decreased by 75% and 33%, respectively. The resistance of oxygen functionalized graphene vs temperature exhibited Arrhenius type behavior with activation energy of 38 meV. The results showed no hysteresis effects in resistance measurements over the temperatures studied here, suggesting the contact interfaces remain stable at high temperatures.