Stacking-fault excitons in AgBr microcrystals with twin planes.

Abstract

The visible emission and excitation spectra of AgBr microcrystals containing single and parallel double twin planes have been obtained. A band at 462.28 nm (2.6813 eV) is observed in the excitation spectrum. This feature is about 2.5 meV below the indirect exciton band edge. Coincident emission features are observed. The band in the excitation spectrum of microcrystals with two parallel twin planes is often split into a doublet with splittings between 1 and 2 meV. The new band is assigned to an exciton created at a stacking fault and the splittings are thought to be due to tunneling of the exciton between proximate twin planes. The small binding energy of the exciton to the twin plane is in accord with the very small strain field about a twin plane.