Abstract
Graphene is considered a promising material for various applications due to its unique physicochemical properties. However, its practical use is limited by the presence of surface‑adsorbed molecules. Acting as dopants, these molecules significantly modify the Fermi level and affect the electrical resistance of the material. In this work, we investigate the effect of thermal annealing in an Ar atmosphere and under high vacuum on the gas‑sensing properties of CVD‑grown graphene transferred onto a SiO2/Si substrate. Annealing exhibits a dual effect: (i) removal of weakly bound dopants (H2O, O2) that initially cause p‑doping, which manifests as an increase in resistance and a change in gas response characteristics; (ii) exposure of structural defects (vacancies, domain boundaries) on the cleaned surface, which become active adsorption sites. As a result, after annealing the interaction with oxygen and water vapor is enhanced: instead of the reversible response typical of physisorption, a stronger interaction with an irreversible component upon pumping is observed. The kinetics of resistance recovery in air follow a biexponential dependence with characteristic times on the order of minutes, indicating at least two readsorption mechanisms (competitive adsorption of H2O and O2, or adsorption on energetically distinct sites). The obtained results demonstrate that thermal treatment enables control over the density of active adsorption sites and, consequently, the gas sensitivity of graphene, but the limited stability of the achieved state in air calls for the development of surface passivation methods to ensure long‑term preservation of the sensing characteristics.
Funding
1. state contract with IT SB RAS - №126021217040-4