Georgia Institute of Technology (Headquarters)

This thesis will present experimental and also theoretical results for the saturation behavior of phosphors under low voltage electron excitation. Over the last twenty years considerable effort has been expended in developing and understanding the cathodoluminescence of high voltage (20kV-30kV) phosphors. However, there is a relative paucity of information available on the physics and performance of phosphors in the low voltage range (0.3 kV-5kV). Experimental measurements for a range of phosphors and comparisons to possible physical models are currently being made to learn more about the physics of low voltage saturation and the nonlinearities in the luminescence vs. excitation curves. In particular, studies of cathodoluminescence emission spectra, efficiency and saturation and decay of luminescence intensity with time under different operating conditions (modulation of the electron beam and variation of electron beam energy) are being made for a range of phosphors. The decay transients and efficiency vs. input power data will be fit to kinetic models that will contain parameters like radiative and nonradiative rates, volume of excited activators and higher order energy transfer rates like excited state cross-relaxation between activators. Mechanisms of energy transfer will be elucidated from Foester-Dexter multipole theory. It is anticipated that the results will lead to an improved understanding of the physics of low voltage cathodoluminescence.