TiO2 thin films were prepared by the reactive magnetron cosputtering technique on the n-type silicon substrates and annealed at different temperatures ranging from 110 to 250 °C. The X-ray diffraction, transmission electron microscopy, and Raman spectroscopy measurements show the formation of TiO2 thin films at 250 °C in the anatase phase (101) with a tetragonal structure. The modification in the electronic structure with the increase of annealing temperatures is studied by the X-ray absorption near-edge structure (XANES) at O K- and Ti L3,2-edges showing the splitting of pre-edge spectral features into t2g (Ti 3d + O 2pπ) and eg (Ti 3d + O 2pσ) symmetry bands in the structural matrix. The intensities of the O K-edge and Ti L3,2-edge increase with the annealing temperature because of induced structural disorder/distortion which could be correlated to the modification in unoccupancies that are associated with the hybridization of O-2p and Ti-3d states. The doublet Ti 2p3/2 and Ti 2p1/2 in Ti 2p X-ray photoelectron spectroscopy (XPS) are revealed with the t2g and eg symmetry bands along with the formation of Ti–O/Ti–OH and/or Ti–O–C bonds observed in O 1s XPS spectra. The estimated work functions (ionization potential) obtained from ultraviolet photoelectron spectroscopy were significantly reduced from ≈4.21 eV (≈7.69 eV) to ≈3.64 eV (≈7.01 eV) when the annealing temperature of the prepared TiO2 thin films is increased from 110 to 250 °C.
Relation:
Journal of Physical Chemistry C 126(20), p.8947-8952
