Structural and chemical network studies of thermal chemical vapour deposited ZnO nanostructured thin films

In this work, we have investigated the role of process temperature on microstructural, structural, vibrational and phonon behaviour of Zinc Oxide Nanostructured (ZnO-NS) thin films deposited via thermal chemical vapour deposition reactor (TCVD) on Si substrate. The various spectroscopic methods such as Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and Raman Spectroscopy were used to evaluate its morphology, structural, vibrational and phononic behaviour. We have observed that the change in process temperature considerably modifies the inherent material properties of ZnO-NS thin films. The AFM result revealed that the density distribution of agglomerated ZnO-nanograins increases with increasing process temperature from 650 degrees C to 750 degrees C. XRD result revealed that the average crystallites size of ZnO-NS thin films was decreased from 22.35 to 12.47 nm with increasing process temperature. The lattice strain and stress in ZnO-NS thin films decrease with increasing process temperature. The FTIR spectra revealed the decreasing intensity of ZnO stretch with increasing process temperature indicates a change in defect distribution of nanostructure at the higher temperature. The Zn-O-H bond shows asymmetry towards the lower wavenumber region can be attributed to the presence of another chemical compound with similar bonding strength overlap with each other. The Raman spectrum confirmed that the FWHM of E1(TO), E2(high), A1(LO) and E1(LO) phonon were increased whereas FWHM of A1(TO) and SO phonon decreased with increasing process temperature. The phonon lifetime of various phonons was calculated using energy-time uncertainty relation and found that the phonon lifetime of E1(TO), E2(high), A1(LO) and E1(LO) phonon decreased with increasing process temperature. (c) 2019 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of the scientific committee of the Third International Conference on Materials Science (ICMS2020).