Noise and modulation experiments on saturated cathodoluminescence from Willemite

Abstract

Measurements of the spectral noise density and a.c. modulation response of saturated cathodoluminescence from polycrystalline Zn2SiO4-Mn (Willemite), are compared with a theory developed by Fijnaut and Zijlstra for the case of characteristic luminescence involving one relaxation time. It was found that, with increasing degree of saturation, the crossover frequencies of the excess noise spectrum and a.c. modulation response are shifted towards higher values, while the plateau value of the excess noise spectrum decreased with increasing degree of saturation. This behaviour was in qualitative agreement with the theory. A quantitative comparison was not possible because of the occurrence of more than one relaxation time in the luminescence under study. The degree of saturation of the luminescence was varied by varying the focussing of the electron beam incident on the phosphor, while keeping the total beam current constant.