Changes of the excitonic optical properties of CdS introduced by an electron beam

Reflection spectra and luminescence in the exciton region of CdS at 80 K under the influence of a low energy electron beam (2 to 3 keV) have been investigated. Long‐term changes of the spectral lineshape have been observed. It is found that the electron beam produces a negative surface charge, the electric field of which dissociates the excitons in a surface layer. The reflected intensity of light is determined by interference of waves reflected at the boundaries of the exciton‐free layer. The lineshape of the reflection spectra depends on the thickness of this layer.