In situ EPR studies of electron trapping in a nanocrystalline rutile

This paper describes an in situ EPR study of electron trapping in a nanocrystalline rutile material. Irradiation at 4 K with broad-band UV–Vis light gives weak signals of trapped electrons. When irradiation is stopped, intense Ti3+ EPR signals appear, which can be removed again by resuming the irradiation. It is proposed that under irradiation there is a dynamic equilibrium established between creation of conduction band electrons, trapping of electrons, and excitation from trap sites back into the conduction band. When irradiation is stopped, conduction band electrons are trapped and remain so in the dark. Some initial results on the temperature and wavelength dependence of these processes are presented.