Structural and Optical Properties of Phase Change Material in Sb2Te3 Thin Film

Chalcogenide based compound, especially Sb₂Te₃ and related compounds, exhibit pronounced structural and optical contrast with rapid phase transition from amorphous and crystalline phase. This makes them suitable candidates for rewritable optical storage media and phase change random access memory. Simultaneously, Sb₂Te₃ have reported that one of the best p-type thermoelectric materials characteristics at room temperature, and topological insulators property. As electron and phonon plays a crucial role in determining the performances of any real devices, a better understanding of the amorphous phase and crystal phase, and the transition mechanism between them, is imperative. Recent, Optical pump THz probe spectroscopy (OPTP) is a powerful tool to study the ultrafast carrier dynamics of structural phase transition occurring on ultrafast time scales, as has been applied to a variety of materials, such as semimetal and semiconductor, and Mott insulators examined by using a femtosecond pump-probe technique and found that the appearance of the coherent vibrational modes was significantly modified upon the phase change.

In this study, we investigate ultrafast carrier dynamics in {Sb(3)Te(9)}_n thin film that the phase change from amorphous into crystalline states can be explained by THz-TDS and OPTP, which is the relationship between structural phase transition and optical properties transition in THz range. We observed that OPTP spectroscopy was closely dependent on phase of the Sb₂Te₃ film, indicating that decay time is a crucial carrier dynamics mechanism to the phase transformation process.