Luminescence of Y2SiO5:Ce Nanocrystalline Thin Films

Abstract

The luminescent properties of cerium doped yttrium silicate (Y2SiO5:Ce) nanocrystalline thin films that were grown during the systematic investigation of process parameters for pulsed laser deposition (PLD) (KrF laser, 248 nm on a silicon (Si)(100) substrate), were studied. Parameters such as ambient pressure (vacuum (5 × 10 -6 Torr), 1 × 10 -2 Torr and 1 Torr O2 pressure), laser fluences (1.6 ± 0.1 J·cm-2 and 3.0 ± 0.3 J·cm-2) and substrate temperatures (400 and 600°C) were varied and the results are compared. The surface morphology was monitored by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and atomic force microscopy (AFM). The monoclinic X1 crystal structures of the Y2SiO5:Ce films were studied with x-ray diffraction (XRD). The O2 ambient pressure of 1 Torr resulted in the growth of a thin film consisting of spherically shaped nanoparticles and the thin film grown in vacuum resulted in a uniform thin film. The cathodoluminescence (CL) and photoluminescence (PL) intensity of the nanofilm is considerably higher than the uniform layer. The higher fluence resulted in a thicker thin film with a more compact agglomerated particle distribution. The lower fluence leads to a higher density distribution of smaller nanoparticles. The increase in substrate temperature to 600°C also resulted in a higher PL intensity. CL scanning images (with two different PMT voltages (650 and 850 eV)) were obtained on some of the thin films during SEM measurements. Emission from the thin films seems to occur from luminescent centres in the micron particles as well as from smaller particles around the bigger micron particles with the higher PMT voltage. [DOI: 10.1380/ejssnt.2009.369]