We report the observations on the structural characterization and optical properties of SnO2nanowires post-treated under different annealing temperatures (300, 400, 500 & 600 °C) for 1 h.
In this study, SnO2 nano‐tube/wire arrays with a diameter in the range of 90‐120 nm and several micrometers in length were synthesized by the liquid phase deposition (LPD) method. The study of structural properties was performed by XRD, Raman and TEM, while the optical properties were measured using UV‐visible absorption and photoluminescence spectroscopy. The Raman spectra of the nano‐tubes/wires revealed the presence of 5 vibration peaks assigned to the tetragonal rutile SnO2 structure in agreement with the XRD results. The estimated optical direct band gap from UV‐visible absorption spectra was found to be 3.73‐3.88 eV. The observed blue shift of the optical band gap can be explained by the higher formation of mesoporous particles on the exposed surface to the photons. The photoluminescence (PL) spectra of the nano‐tubes/wires exhibited a rather broad and intense emission band centered at around 560‐569 nm.
In this work, anatase and rutile TiO 2 nanorods were fabricated using one-step liquid phase deposition process, followed by heat treatment in the range 300-800°C.The direct and indirect band gap of the TiO 2 nanorods was estimated form optical absorption data which illustrated a red shift at higher temperatures owing to the different nature of excitons in anatase and rutile phases. The photoluminescence (PL) spectra revealed the presence of two main emission bands consisting of four peaks.It was found that two high-energy peaks located at 2.95-3.30 eV could be generated from exciton transitions from the conduction band to the valence band of TiO 2 nanorods, while two low-energy peaks located at 2.43-2.64 eV may arise from surface state transitions. The PL intensity firstly increased with temperature and at 500°C reached a maximum value, then decreased through increasing temperature up to 800°C. These variations in the intensity of PL emission could be explained in terms of changes in phase structure, crystallinity, and amount of the oxygen vacancies, which are all dependent to the annealing temperature based on X-ray diffractometer and X-ray photoelectron spectrometer studies. These results indicated that annealing temperature allows to manipulate the properties of TiO 2 nanorods for opto-electronic applications.
K E Y W O R D Sannealing temperature, photoluminescence, polycrystalline TiO 2 nanorods, UV-visible absorption, XPS analysis 2430 |
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