Cathodoluminescence study of defects in deformed (110) and (100) surfaces of TiO2 single crystals

In this work, the effect of different surface orientations on the defect structure of TiO2 single crystals and the evolution of the luminescence properties under plastic deformation are investigated by cathodoluminescence (CL) microscopy. The main features of the spectra are an infrared band at 1.53 eV, and a complex band in the visible range, whose peak position depends on the electron beam energy, and is attributed to oxygen vacancy related defects. Comparison of the intensity of these bands in the spectra recorded at low electron beam voltage indicates that the Ti3+ defects present a higher concentration at the (110) surface, whereas the (100) surface presents a more complex defect structure related to the oxygen vacancies. Competition is observed between the visible and the infrared emission centres during plastic deformation of the samples in agreement with the different diffusion mechanisms of the defects involved in the emissions.