Low-Energy Au Ion Beam Implantation in the Optical, Structural, and Surface Properties of RF-Sputtered WO₃ Thin Films

WO₃ is considered to be significant for diverse applications such as gas sensing, photocatalysts, and photovoltaic devices because of its optical wide band gap. Ion beam treatment of various metal oxides produces defects that modify various properties such as topographical, structural, and optical characteristics of the metal oxides. When the energetic ion pass through the target materials, it causes two kinds of energy losses, i.e., nuclear and electronic energy loss. In low-energy ion beam treatment of thin films, nuclear energy loss dominates over electronic energy loss. In our current study, thin films of tungsten oxide were grown on substrates of glass and silicon by the RF-sputtering method. The sputtered WO₃ thin films were exposed to an ion beam of Au iosn with an energy of 80 keV at various fluences of 5E14 ions/cm², 1E15 ions/cm², and 5E15 ions/cm². Atomic force microscopy (AFM) shows that, after implantation, enhancement in grain size was observed from 49.5 nm to 56.6 nm. The optical study displays the alteration in the energy band gap of ion-implanted WO₃ thin films from 2.75 eV to 2.99 eV. From Raman spectroscopy, the phase observed is monoclinic for virgin and implanted samples. PL spectroscopy of virgin and ion beam-implanted WO₃ thin films shows emission spectra at the wavelength of 580 nm at an excitation wavelength of 420 nm. X-ray photoelectron spectroscopy shows the appearance of tungsten and oxygen atoms and shows the electronic structure variation after Au ion beam implantation.