Cathodoluminescence from thin film Zn2GeO4 : Mn phosphor grown by pulsed laser deposition

Low voltage cathodoluminescent (CL) characteristics of Zn2GeO4 : Mn thin-film phosphors grown by pulsed laser deposition were investigated. The effects of substrate heating (600-750 degreesC) and substrate type (MgO, Si, and yttria-stabilized zirconia) on the cathodoluminescent properties were studied. A characteristic green emission peak at 540 nm was observed at substrate temperatures of 650, 700, or 750 degreesC. However, the emission was red shifted to 650 nm for a substrate temperature of 600 degreesC. The red shift in emission wavelengths from 540 to 650 nm was attributed to a change in ionic state of the activator from Mn2+ to Mn4+. While the spectral position was independent of substrate type, the relative intensities of the cathodoluminescent emission peak varied with both substrate type as well as substrate temperature. At a substrate temperature of 600 degreesC, the crystal structure of the film was mixed polycrystalline and amorphous. However, at substrate temperatures ranging from 650-750 degreesC, the films were only polycrystalline with varying degrees of crystallinity that correlated with the CL intensity. (C) 2004 The Electrochemical Society.