LUMINESCENCE PROPERTIES OF INDIRECT BANDGAP SEMICONDUCTORS - NANOCRYSTALS OF SILVER BROMIDE

Using a modified reverse micelle protocol with acetyl bromide as the b romide source, AgBr nanocrystals can be grown over a size range from 3 0 Angstrom radius to bulk. These clusters exhibit quantum confinement indicated by an increasing blue shift of the free exciton emission pea k 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 dia meters. However, the effects are quite modest, indicating that even at these smallest sizes, the indirect character of the transition is lar gely retained.