Dielectric properties and soft modes in semiconducting (Pb, Sn, Ge)Te

摘要: The narrow-gap semiconductors PbTe, SnTe, GeTe and their alloys exhibit a tendency for ferroelectric displacive phase transition from high-temperature rocksalt structure to rhombohedral at low temperatures. critical temperatures vary within an exceedingly wide range: −70 K(PbTe) up 650 K(GeTe). Owing the outstanding simplicity of crystal well-known electronic properties, instability chemical trends Tc can be understood in terms quantitative pseudopotential model (Sect.5.2). Phenomenological models explain temperature dependence soft mode outside regime fairly well (Sect.5.1). Critical phenomena, however, deserve further attention: anomalies static dielectric constant (Sects.3.1 5.3) influence defects are possibly related central peak. Additional systematic investigations on nature required obtain more insight into this highly interesting field general importance.