Stability investigation of Eu3+ doped CaF2 thin film with ZnO coating under electron beam irradiation

Eu3+ ion doped CaF2 thin film was successfully prepared using the hydrothermal method and coated by a spin coating technique. A thin layer of ZnO was deposited on the Eu3+ doped CaF2 thin film by pulsed laser technique. Incorporation of the dopant into the CaF2 crystal was confirmed by x-ray powder diffraction and x-ray photoelectron spectroscopy (XPS). Excitation of the film at 227 nm produced the characteristic emissions of Eu3+ ions. The stability of the film under electron beam bombard was studied using Auger electron spectroscopy, cathodoluminescence (CL), and XPS. The CL and Auger peak-to-peak heights (APPHs) data were collected concurrently using the same electron beam. The APPH of Ca and O increased, while that of F decreased, which indicated the conversion of CaF2 to CaO. The CL emission decreased initially during degradation and stabilized beyond 48 C/cm2 for the film with the ZnO coating. XPS analysis also indicated the dissociation of the fluoride compounds and subsequent formation of oxide compounds such as CaO and EuO after electron beam degradation.