The location of silver dopants in lead halide single crystals

Lead(II) bromide and chloride have been purified by zone refinement and these purified products are grown into large device quality single crystals by the Bridgman-Stockbarger technique. Cracking on cooling is observed especially in the case of lead bromide. To alleviate this problem, doping with silver bromide at the level of 0.05-0.5 mol% is shown to eliminate cracking. The role of the dopant is unclear, but is presumably associated with the location of the ion within the host lattice. Extended X-ray Absorption Fine Structure (EXAFS) analysis was performed at Daresbury Laboratories to determine this role and it was found to be a simple substitution into the crystal lattice.