Characterization of luminescent samarium doped HfO₂ coatings synthesized by spray pyrolysis technique

Trivalent samarium (Sm³⁺) doped hafnium oxide (HfO₂) films were deposited using the spray pyrolysis deposition technique. The films were deposited on Corning glass substrates at temperatures ranging from 300 to 550 °C using chlorides as raw materials. Films, mostly amorphous, were obtained when deposition temperatures were below 350 °C. However, for temperatures higher than 400 °C, the films became polycrystalline, presenting the HfO₂ monoclinic phase. Scanning electron microscopy of the films revealed a rough surface morphology with spherical particles. Also, electron energy dispersive analysis was performed on these films. The photoluminescence and cathodoluminescence characteristics of the HfO₂ : SmCl₃ films, measured at room temperature, exhibited four main bands centred at 570, 610, 652 and 716 nm, which are due to the well-known intra-4f transitions of the Sm³⁺ ion. It was found that the overall emission intensity rose as the deposition temperature was increased. Furthermore, a concentration quenching of the luminescence intensity was also observed.