AVS 51st International Symposium
    Thin Films Wednesday Sessions
       Session TF-WeM

Paper TF-WeM6
Infrared Emission from Zinc Sulfide Doped with Rare Earth Fluorides

Wednesday, November 17, 2004, 10:00 am, Room 303C

Session: Optical Thin Films
Presenter: D. DeVito, University of Florida
Authors: D. DeVito, University of Florida
A. Kale, University of Florida
W. Glass, University of Florida
M. Davidson, University of Florida
P.H. Holloway, University of Florida
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Thin film electroluminescent devices are excellent sources for high efficiency infrared emission. Rare earth elements, such as Erbium, Thulium and Dysprosium, are good dopants for infrared emitting phosphors because of the many transitions they exhibit in the infrared region. Zinc sulfide is a stable, wide bandgap semiconductor in which electrons can be excited to appropriate energies to produce excitation of the luminescent centers. Achieving good brightness requires a combination of precise composition, deposition conditions and post-deposition annealing. Lanthanide doped zinc sulfide electroluminescent thin films were deposited from two planar magnetron sources using ZnS and lanthanide trifluoride targets. Infrared emission from devices shows a marked improvement for films annealed at temperatures above 350°C. Maximum brightness was achieved for samples annealed at 425°C and, based on SIMS data, is associated with a reduction in the fluorine concentration in the films. Mechanisms for the loss of fluorine include solid state diffusion, with replacement of F with S on the substitutional site. The mechanism for increased electroluminescence will be discussed based on oscillator transition strength relative to nearest neighbor bonding.