title: Contrast and decay of cathodoluminescence from phosphor particles in a scanning electron microscope.
abstract: Cathodoluminescence (CL) studies are reported on phosphors in a field emission scanning electron microscope (FESEM). ZnO: Zn and other luminescent powders manifest a bright ring around the periphery of the particles: this ring enhances the contrast. Additionally, particles resting on top of others are substantially brighter than underlying ones. These phenomena are explained in terms of the combined effects of electrons backscattered out of the particles, together with light absorption by the substrate. The contrast is found to be a function of the particle size and the energy of the primary electrons. Some phosphor materials exhibit a pronounced comet-like structure at high scan rates in a CL-image, because the particle continues to emit light after the electron beam has moved to a position without phosphor material. Image analysis has been used to study the loss of brightness along the tail and hence to determine the decay time of the materials. The effect of phosphor saturation on the determination of decay times by CL-microscopy was also investigated.
authors.affiliation: Centre for Phosphor and Display Materials, Wolfson Centre for Materials Processing, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: den Engelsen
authors.affiliation: Centre for Phosphor and Display Materials, Wolfson Centre for Materials Processing, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Harris
authors.affiliation: Centre for Phosphor and Display Materials, Wolfson Centre for Materials Processing, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK. Electronic address: terry.ireland@brunel.ac.uk.
authors.forename: Terry G
authors.initials: TG
authors.lastname: Ireland
authors.affiliation: Centre for Phosphor and Display Materials, Wolfson Centre for Materials Processing, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK.
authors.forename: George R
authors.initials: GR
authors.lastname: Fern
authors.affiliation: Centre for Phosphor and Display Materials, Wolfson Centre for Materials Processing, Brunel University London, Uxbridge, Middlesex UB8 3PH, UK.
authors.forename: Jack
authors.initials: J
authors.lastname: Silver
keywords: Backscattered electrons; Interaction volume; Phosphor powder; Phosphor saturation; Secondary electrons