Effect of low energy (keV) ion irradiation on structural, optical and morphological properties of SnO2–TiO2 nanocomposite thin films
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RF Sputtering deposition technique was used to deposit the thin films of nanocomposite oxides as SnO2–TiO2 on Si and ITO coated glass substrate. As a target, SnO2–TiO2 was taken according to their molecular weight percent ratio of 3:1. Material modification has been induced by low energy ion beam with varying ion fluence from 5E13 to 5E16 ions/cm2. Glancing Angle X-ray Diffraction technique was used to study crystallite size, phase transformation and stability of different planes of pristine and irradiated thin films. The important peaks observed in XRD pattern were at angles 26.95°, 34.27°, 37.60°, 50.88° and 52.46°. The grain size distribution and surface morphology were studied by Atomic Force Microscopy technique in tapping mode. The results show that the grain size varies with ion fluence. Raman analysis revealed that the sharp peak at the frequency of 520 cm−1 ascribed to the T2g mode was observed for the pristine and lowest fluence irradiated film deposited on Si substrate. With increasing ion fluence, an opposite trend in SnO2 B2g peak was observed at nearly 775 cm−1 and the also peak bump was observed as a function of ion beam fluence. The optical band gap decreases from 3.90 to 3.63 eV due to the generation of ions and free radicals in valance band by varying ion fluence which was observed by UV/Visible Spectroscopy. The film thickness was determined to be 220 nm using Rutherford Backscattering Spectrometry. It also confirmed the absence of any impurities in the pristine and irradiated thin films. The material properties were mainly modified by the point defects and grain size growth arising due to nuclear energy loss.
One of the authors, Dr. Rajesh Kumar is grateful to Inter University Accelerator Center (IUAC), New Delhi, India for providing financial assistance (Ref: IUAC/XIII.3A/59319) and the University Grants Commission, Govt. of India, New Delhi, India, as Raman Post Doctoral Fellow (F. No. 5-150/2016(IC) for carrying out this research work.
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