Low-temperature technology and physical processes in green thin-film phosphor Zn 2 GeO 4 -Mn
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Low-temperature technology and physical processes in green thin-film phosphor Zn2GeO4-Mn V.Bondar, S.Popovich, T.Felter1, and J.Wager2 Lviv National University, Department of Physics, 50 Dragomanov Str., 79005, Lviv, Ukraine. 1 Lawrence Livermore National Laboratory, PO Box 808, L - 356, Livermore, CA, 94550 2 Department of Electrical and Computer Engineering, Oregon State University, Corvallis, Oregon 97331-3211, U. S. A ABSTRACT Thin-film Zn2GeO4:Mn phosphors with lower temperature of crystallization and potentially compatible with industrial technologies were investigated. The technology of thin films synthesis has been developed and their structure and crystal parameters have been investigated. Photoluminescence excitation spectra, photoconductivity, temperature dependencies and ESRspectra of manganese ions were studied. A mechanism for luminescence in this phosphor has been proposed. Results are presented of cathodo- and electro-luminescence of thin film structures of Zn2GeO4:Mn.
INTRODUCTION The manganese dopant is one of the most efficient centers of luminescence in phosphors. Together with high efficiency, one additional advantage is the color of emission, which depends on the crystal lattice: yellow in ZnS:Mn, green in Zn2SiO4:Mn, or blue-green in ZnG 2O4:Mn. Oxide phosphors are more stable in comparison to sulfide ones and therefore are promising for flat panel display applications. However, the use of oxide thin-film phosphors in many cases is limited because of their high crystallization temperature. For this reason, a series of recent works [1, 2, 3] was directed on the development of phosphors with lowered crystallization temperature. In the present work, we developed the technology of synthesis of thin-film Zn2GeO4:Mn phosphors with lower crystallization temperature. Thus, these phosphors may be compatible with industrial technologies. We also investigated the crystal structure of thin films and the luminescent processes caused by manganese dopant.
EXPERIMENTAL Zn2GeO4:Mn films were deposited by rf-magnetron sputtering [4] of a pressed target manufactured from the presynthesized powder corresponding to the stoichiometric composition of Zn2GeO4:Mn2O3. The quality of thin films depends on deposition conditions and was assessed by absorption edge position, refractive index, and transparency of the films in the visible region obtained from optical measurements. The film structure was investigated using an HZG-4A Xray powder diffractometer (CuKα radiation, θ-2θ scan mode, step 0.05°, t=10 s per point). The Rietveld profile refinement method of analysis of experimental XRD data was used [5, 6]. Specified parameters were unit cell parameters and a texture parameter [7]. The X-band (ν≅9.4 GHz) ESR spectra were recorded using a computer controlled commercial AE-4700 radio G7.6.1
frequency spectrometer with 100 kHz magnetic field modulation at room temperature. The microwave frequency was controlled by means of diphenylpicrylhydrazyl (DPPH) g-marker (g=2.0036±0.0001). Cathodoluminescence spectra were measur
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