Dislocations and Glide in Lead Sulfide as a Function of Deviations from Stoichiometry and Doping Additions

Point defects induced in PbS by slight deviations in chemical composition about the stoichiometric ratio were shown in a qualitative experimental study to affect dislocation density and strength. A very small but reproducible increase in dislocation density was observed by an etch-pit method in single crystals of PbS and in silver-doped PbS having excess sulfur or excess lead as compared with the stoichiometric composition. With a prismatic punching technique to obtain a measure of the yield strength, a slight increase in strength was found to correlate with an increase in point defect concentration in PbS. An etch-pit and slip-line analysis of glide in stoichiometric PbS verified the single primary glide system {100}〈110〉.