Lattice dynamics of Cd-rich Cd1−xHgxTe alloys

An investigation is made of the lattice dynamics of low concentration of Hg atoms (x < 0.3) in Cd-rich Cd1−xHgxTe mixed system. The vibrational mode frequency for the isolated Hg replacing Cd atoms in CdTe is observed at 131 cm−1. The impurity is described by a perturbation model that accounts for the change of mass at the impurity site as well as the local variation of nearest-neighbour forces. A calculation based on the Green's function theory suggests stiffening in nearest-neighbour forces (Δf/f = +0.25) due to isolated Hg in CdTe system. On etudie la dynamique de reseau des alliages Cd1−xHgxTe du cǒte riche en cadmium (x < 0,3). La frequence du mode vibrationnel du mercure en substitution isolee sur site Cd est trouvee egale a 131 cm−1. Ce cas est discute en connexion avec la variation locale des forces introduites par la presence du defaut. Un calcul base sur une technique de fonctions de Green revele que l'introduction du mercure isole (x = 0) conduit a un net renforcement des forces entre l'impurete et ses premiers voisins (Δf/f ≈ +0,25).