Structural, optical and vibrational properties of sol-gel deposited ZnO thin films

In the present study, poly crystalline ZnO thin films fabricated on ultrasonically cleaned glass substrate by sol-gel spin coating technique. X-Ray diffraction (XRD), UV-Visible spectroscopy (UV-Vis.), scanning electron microscopy (SEM), and Raman spectroscopy are used to characterize the fabricated ZnO thin films. The X-Ray diffraction (XRD) pattern confirmed that the ZnO thin films are polycrystalline in nature. It is found hexagonal wurtzite structure with a preferential orientation of (002) plane at 2θ =34.4°. The absorbance spectra of the synthesized ZnO thin films showed that maximum absorbance in the wavelength range of 200 to 280 nm. The optical band gap of the synthesized ZnO thin films is found to be 3.18 eV, direct allowed transition. The Raman spectra of ZnO thin films confirmed that the space group of the hexagonal wurtzite ZnO thin films belongs to C46v. The peak at 433 cm-1 is attributed to ZnO optical phonon E2 (high) mode, which also demonstrates that the ZnO thin films are highly c-axis oriented. The peak at 391 cm-1 corresponds to A1(TO) phonons, which can result from the defects such as oxygen vacancy, zinc interstitial or their complexes and free carriers. (author)