Photolumineseence, Electroluminescence, and Cathodoluminescence of ZnO:Zn Phosphor Films Prepared by MOCVD

Abstract

AbstractCathode ray tube (CRT) technology remains the major display component for today's display technologies. The improvements from monochrome displays to today's full color displays have always been accompanied by improvements in the phosphors. The CRT type displays operate at very high voltages (over 10 keV) at relatively low currents, a few microamps/cm2. The phosphors and phosphor coating technology used in CRT based displays have been optimized for operation with these excitation conditions. However, the developments of field emitter displays based on microtip technology, or negative electron affinity technology require phosphors that operate at lower voltages, preferably 10 to 1500 eV at relatively higher current densities. Zn-rich zinc oxide (ZnO:Zn) powders have shown improved low voltage cathodoluminescence (CL) as compared to conventional ZnS based phosphors. ZnO:Zn thin film phosphors for cathodoluminescent displays, compared to conventional powder phosphors, can have the advantages of high electrical and thermal conductivity, high energy saturation limit, and high screen resolution. The photoluminescence (PL), Electroluminescence (EL), and CL from thin ZnO:Zn films were studied. The samples were prepared by Low Pressure Metal Organic Chemical Vapor Deposition (LP MOCVD) and post-annealed at temperatures from 700 °C to 1000 ° C. The PL, EL, and CL spectra have a peak centered at 590 nm that increases with annealing temperatures up to 1000 °C. The CL efficiencies are 0.12 Lm/W at electron voltages and currents as low as 500 V and 64 mA/cm2. The ZnO films have been characterized by X-ray Diffiractometry (XRD), and Sweep Electron Microscope (SEM). These PL, EL, and CL results from ZnO:Zn films show the promise for improved phosphors to meet Field Emitting Device (FED) challenges.