Electron beam induced nanostructures and band gap tuning of ZnO thin films

Highlights: ► High energy electron beam irradiation is done on ZnO thin films. ► The formation of nanostructures is observed. ► The dimensions of nanostructures are dependent on electron energy. ► Optical constants and band gap energy can be tuned by varying electron energy. -- Abstract: The present work deals with the formation of nanostructures and tuning of optical band gap of ZnO thin films by high energy electron bombardment. In first step, Zinc Oxide (ZnO) thin films were deposited on silicon (1 0 0) substrates by pulsed laser deposition (PLD) technique using KrF Excimer laser. In second step, ZnO thin films were irradiated by electron beam of energy 6, 9, 12 and 15 MeV at constant dose. The surface morphology was studied by Atomic Force Microscope (AFM), whereas the optical properties were determined by Spectroscopic Ellipsometry (SE). Atomic force micrographs showed the formation of nanoscale structures on the surface of ZnO thin film. The nanostructures grew in size and reached its maximum size at 12 MeV electron energy. SE analysis revealed the increase in refractive index, appearance of broad absorption peak in visible region, and increase in optical band gap energy of ZnO thin film by 12 MeV electron bombardment. From the results, it can be concluded that the size of nanostructures and the optical band gap energy of ZnO thin films can be tuned by electron irradiation at various energies