where Ra and Rd are the rates of adsorption and desorption, respectively; Ea and Ed are the activation energies of adsorption and desorption, respectively; T is the temperature; K and Kare the adsorption or desorption rate constants; is the fraction of surface occupancy; f() is a function related to surface vacancy, (1 − );and f() is a function related to surface occupancy (). Based on the above equations, Ra increases with increasing gas pressure and function of surface vacancy, whereas it decreases with higher activation energy of adsorption. Rd increases with increasing desorption temperature and function of surface occupancy, whereas it decreases with higher activation energy of desorption [38]. As a result, thermal annealing is favorable for desorption, thus enhancing the recovery of the sensors.