Precipitation of tellurium in (Hg, Cd)Te alloys

Abstract

The precipitation of tellurium in alloys of Hg1−xCdxTe with x = 0.2 to 0.3 prepared under conditions of excess tellurium by the solid state recrystallization method have been studied using chemical defect etching and transmission eloctron microscopy. Precipitation of tellurium occurred during the quench from the recrystallization anneal. During the initial part of the quench, precipitation occurred as a result of nucleation of precipitates on pre-existing dislocations. This precipitation resulted in the formation of dislocation helices with precipitates in the interior of the helix loops. Both monoclinic and trigonal phases of tellurium were found in these precipitate defects, as well as the twinned matrix phase. Later in the quench, an additional nucleation mechanism, either homogeneous or heterogeneous on an impurity occurs resulting in the formation of complex defects in the bulk. During a subsequent post-anneal at temperatures of approximately 300°C, the tellurium precipitates dissolve, and interstitial perfect and faulted dislocation loops are formed. Both the precipitation process and the subsequent post-annealing result in considerable multiplication of dislocations.