Quenching of visible photoluminescence and observation of two photon absorption-induced photoluminescence in pulsed laser deposited Zn1−xTixO (0.000 ⩽ x ⩽ 0.050) thin films

Abstract

Single and two photon absorption-induced UV photoluminescence (PL) from pulsed laser deposited Zn1−xTixO (0.000 ⩽ x ⩽ 0.050) thin films grown onto fused silica substrate is reported in the present paper. Preferred orientation in the (0 0 2) plane is exhibited by the film grown at x = 0.020 composition, while the rest of the films are polycrystalline in nature as depicted by x-ray diffraction measurement. The surface morphology of the films shows mixed features of spherical and flower-like nanostructures. The PL spectra recorded under single photon excitation (using a continuous wave He:Cd laser, 325 nm) demonstrate near band edge emission centered at ~380 nm and a broad visible band emission in the range 420–730 nm. Enhancement in the UV emission and simultaneous reduction in the visible band in the films with 0.000 ⩽ x ⩽ 0.020 are observed. The film grown with x = 0.020 completely eradicates the visible band emission, while the UV emission is enhanced by an order of magnitude. The reinforcement in UV-PL is a result of the quantum size effect in the films. PL under multiphoton absorption is exhibited by the films under optical excitation by a continuous wave He:Ne laser, operating at a wavelength of 632.8 nm. The UV-PL peak positions in the films are observed at relatively high photon energy as compared to those of the UV-PL via single photon excitation. The slope, m, of the log–log plot of PL intensity versus excitation intensity falls in the range 1.01–1.46, suggesting two photon absorption-induced PL in the films.