LUMINESCENCE PROPERTIES OF INDIRECT BANDGAP SEMICONDUCTORS - NANOCRYSTALS OF SILVER BROMIDE

Using a modified reverse micelle protocol with acetyl bromide as the bromide source, AgBr nanocrystals can be grown over a size range from 30 Angstrom radius to bulk. These clusters exhibit quantum confinement indicated by an increasing blue shift of the free exciton emission peak as a function of size. As the cluster size decreases, a concomitant decrease occurs in the apparent radiative lifetime. This is predicted as the ($) under bar k selection rules break down at small crystal diameters. However, the effects are quite modest, indicating that even at these smallest sizes, the indirect character of the transition is largely retained.