Pulsed laser deposition of Y2O3 : Eu thin film phosphors
Thin films of Y2O3 : Eu cathodoluminescent (CL) phosphors were deposited using pulsed laser deposition using deposition temperature between 250 degrees C and 800 degrees C, O-2 pressures between residual vacuum (2 x 10(-5) Torr) and 6 Torr, and post annealing up to 1200 degrees for 1 h in air. The CL efficiency of the best thin film was about one third that of the starting powder. The brightness and efficiency of the thin films improved as the deposition temperature, O-2 pressure and post annealing temperature were increased, except that O-2 pressures above 600 mTorr did not significantly improve the CL properties. At deposition temperatures > 600 degrees C, the surface morphology changed from a smooth film to a nodular deposit for O-2 pressures > 200 mTorr, with nodule dimensions approximate to 100 nm. Simultaneously, the CL properties improved dramatically because of enhanced optical scattering out of the thin film. Optical scattering was discussed in terms of anomalous diffraction. The CL properties also improved dramatically with high temperature post annealing. This effect was interpreted in terms of improved crystallinity and activation of the Eu. The low brightness and efficiency of thin films versus powder was affected by depletion of the Eu in the thin films owing to the deposition process. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
cathodoluminescence diffraction crystallinity