Characterization of multilayer TiO 2 /ZnO nanostructured thin films using Raman spectroscopy

The aim of this paper is to characterize TiO2/ ZnO multilayer thin films using Raman spectroscopy. The TiO2/ZnO films were prepared using the sol-gel spin coating method. Additionally the surface morphology and crystal structure of thin films were characterized by means of profilometry. The profilometer results showed that the surfaces of the samples are not uniform. The thickness of the sample was identified in the µm range. Raman spectroscopy revealed a sharp and strong peak at 436.9 cm −1 due to ZnO. The observed peak is assigned as the optical phonon E2 mode which is a characteristic Raman-active peak for the wurtzite hexagonal phase of ZnO. The TiO2/ZnO substrate exhibited many peaks. The existence of the 436.9 cm −1 peak in the TiO2/ZnO thin film confirmed the E2 mode of ZnO. The appearance of three peaks, 395.6 cm −1 , 514.9 cm -1 and 629.7 cm -1 , confirmed the anatase TiO2 phase, and the peak at 342.5 cm −1 confirmed the rutile TiO2 in the TiO2/ZnO. The presence of all corresponding ZnO and TiO2 peaks in the Raman scattering indicate that the TiO2/ZnO thin-film substrates exist as a mixed crystalline structure of both materials.