Stability of group IV-VI semiconductor alloys

We present transmission electron microscopy results on Pb_1-x{Eu}ₓTe alloys that show evidence for a compositional instability for x0.5 when the alloys are grown on{BaF}₂$ substrates. The ${Pb}_{1{{-}}x}EuₓTe alloy becomes stable at room temperature if a buffer layer of PbTe is grown on the BaF₂ substrate prior to the growth of the Pb_1-x{Eu}ₓ$Te layer. The stabilization of the ${Pb}_{1{{-}}x}EuₓTe solid solution is the result of the additional energy term due to the strain between the Pb_1-x{Eu}ₓ$Te film and the PbTe buffer layer. The estimated critical temperatures for decomposition of the ${Pb}_{1{{-}}x}EuₓTe alloys with and without the PbTe buffer layer are {}0 and {}366 K, respectively, in accord with the experimental observations.