Noise in cathodoluminescence radiation from a (CaMg)(SiO3)2-Ti phosphor

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Abstract
Fluctuations occurring in cathodoluminescence light stemming from a CMT-7 phosphor were measured in the frequency range 01-40 kHz. The observed noise consists of a frequency-independent part corresponding to full shot noise, and a frequency-dependent part. The latter can be considered amplified cathode beam noise, the frequency dependence of which is associated with a lifetime of 28 μs of the excited state of the luminescence centre. The amplification itself is due to the fact that a bombarding electron may excite several luminescence centres, depending on its energy. The theoretical interpretation is based on a Langevin approach considering a two-level model for the luminescence centre. The de-excitation process is considered spontaneous, whereas the excitation process was considered analogous to the process of secondary emission, the noise of which has been calculated by Shockley and Pierce. It is shown that noise measurements are useful for the evaluation of the energy efficiency of phosphors.

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