Photoluminescence properties of SrAl₂ O₄: Eu ²⁺, Dy³⁺ thin phosphor films grown by pulsed laser deposition

Thin films of SrAl₂ O₄: Eu²⁺, Dy ³⁺ phosphor were deposited on silicon [Si (100)] substrates using a 248 nm KrF pulsed laser. Deposition parameters, such as substrate temperature, pulse repetition rate, number of laser pulses, and base pressure, were varied during the film deposition process. Based on the x-ray diffraction data, all the films were amorphous but were emitting visible light when excited by a monochromatic xenon lamp. The chemical composition and the stoichiometry of the films determined by the Rutherford backscattering spectroscopy were consistent with the commercial SrAl₂ O₄: Eu²⁺, Dy ³⁺ powder used to prepare the films. Photoluminescence (PL) emission spectra of the films were characterized by major green emission with a maximum at ∼520 nm and minor red emission with a maximum at 630 nm. The green and red photoluminescence at 520 and 630 nm are associated with the 4 f⁶ 5d→4 f⁷ (⁸S_7/2) and ⁵D ₀ - ⁷F₂ transitions of Eu²⁺ and residual Eu³⁺ ions, respectively. Brighter films were shown to have relatively higher values of the root mean square surface roughness, which were determined from the atomic force microscopy data. The effects of processing parameters on the PL intensity are discussed.