Monitoring dynamics of different processes on rutile TiO2(110) surface by following work function change

Time evolution of the work function (WF) change of TiO2 (110) rutile surface due to the oxygen adsorption and electron bombardment has been investigated. Oxygen adsorption has been performed on surfaces prepared in different ways (annealing temperature, in UHV or in oxygen atmosphere) which have different amounts of bridging oxygen vacancies (BOVs). The surfaces having low amount of BOVs were used in electron bombardment experiments. WF increases due to the O2 adsorption, and the overall change increases with the amount of BOVs. The result is consistent with the BOV healing by O2 adsorption. Oxygen adsorption results can be correlated with the shape of the Ti 2p photoelectron line: there is a linear dependence between the total WF change and the relative amount of the Ti3+ contribution in the Ti 2p3/2 line up to 0.2 eV when WF change reaches the saturation. Electron bombardment reduces WF due to the well known process of electron stimulated desorption of oxygen from bridging oxygen sites. The total change reaches about 0.5 eV, when the saturation is reached. It was shown that the efficiency for creating BOVs by electron bombardment increases with the electron energy.