Scanning Electron Microscope Induced Cathodoluminescence

Abstract

Luminescence is a process in which radiation is emitted by molecules or atoms that have been excited by the absorption of radiation. Accelerated electrons have energies very much greater than the quantized levels of atoms and molecules and in passing through a substance, detach bound electrons. A plasma (ion-electron gas) is formed and as recombinations occur, light quanta are emitted. Thus, if one uses accelerated electrons as the source of exciting radiation, observations of cathodoluminescence (CL) may often be made.Much of the energy absorbed is lost in processes other than luminescence. Losses by internal conversions may occur which involve intersystem crossing from the excited singlet state to the triplet state (phosphorescence or heat) or through predissociation (disruption of chemical bonds in the compound). Energy loss by external conversion (quenching) may also occur through collisions with other molecules (radiationless energy transfer or heat).