Cathodoluminescence Saturation Phenomena in Y 2 O 2 S : Eu

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Abstract
The importance of a thermal perturbation of (0.1%) under excitation by long (up to 30 msec) electron beam pulses is investigated using the measured differential thermal behavior of luminescence lines originating in the , , and states. An observed droop in light output, equivalent to a saturation of the phosphor brightness, is found to be inconsistent with a thermal perturbation of the system. Other experiments involving a‐c electric field modulation of the luminescence from the states suggest that the droop may be caused by electric field perturbation of the system. The saturation characteristics of the phosphor are changed reversibly during a 30 msec pulse, and irreversibly by mixing with a conducting matrix. It is suggested that space‐charge fields are generated by trapping of charge in surface states of the phosphor grains, and a simple kinetic model for the saturation mechanism involving field‐induced ionization of the charge transfer state and quenching of the state is in qualitative agreement with the experimental data. The relevance of the model to saturation phenomena and to aging in CRT screens is discussed.

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