Improved optical absorption, enhanced morphological and electrochemical properties of pulsed laser deposited binary zinc and vanadium oxide thin films

The investigations were carried out on binary metal oxide ZnO/V₂O₅ nanostructured thin films prepared by pulsed laser deposition for the MOSFET channel application. The thin films were prepared at 298 (as deposited), 623, 773, and 923 K at 10 Hz laser repetition rate (LRR) for 30 min. The films were characterized by SEM, EDAX, XRD, UV–Visible spectroscopy, and IV measurements. The amorphous nature of the film deposited below 773 K was revealed by XRD analysis. Few diffraction peaks were seen in the 923 K sample, revealing the formation of Zn₂V₂O₇ and Zn₃V₃O₈ in the binary ZVO thin films. All the samples are partially or completely amorphous in nature till 923 K. The optical energy bandgap was measured using Tauc plot and it was found to be 3.1–3.7 eV for the ZVO thin films. Then, the films were investigated by impedance and modulus spectroscopy over a frequency range of 1 Hz–1 MHz and temperatures lying in the 298–473 K domain. The frequency response of the imaginary impedance (Z″) shows a relaxation behavior for each measuring temperature in all the three samples. However, four samples were fabricated, namely, at 298 (as deposited), 623, 773, and 923 K. The three binary metal oxides pulsed laser deposited at high temperatures show a semiconducting behavior. The activation energy (E_a) was determined from the Arrhenius plot based on impedance and modulus relaxation. The activation energy is minimal for the high-temperature PLD thin films.