Green and Ultraviolet Emissions From Anatase TiO2 Films Fabricated by Chemical Vapor Deposition

Luminescence properties of anatase TiO2 films grown on sapphire substrates by atmospheric chemical vapor deposition have been investigated over a wide temperature range of 20 K to 300 K. An intense green emission band associated with localized exciton recombination has been observed at low temperatures under photoexcitation. The emission exhibited temperature quenching with an activation energy of ∼48 meV. The shape of the emission spectrum was considerably modified upon electron beam excitation. The principal feature of this modification is a reversible redistribution of the spectrum intensity, which causes the appearance of a new UV emission band at high acceleration voltages. Details of the mutual relationship between the green and UV emission processes are considered in terms of the linear coupling configuration coordinate model. We propose that the temperature quenching of green emission is attributed to a combination of various thermally stimulated processes within the configuration coordinate diagram and energy migration through the excited state of the UV emission.