Effect of Pb doping on the crystallization process and thermoelectric properties of Ge2Sb2Te5 phase change material

Abstract

Phase change materials based on Ge-Sb-Te alloys are widely explored for their potential in both memory devices and thermoelectric applications. In this study, films of Ge2Sb2Te5 (GST) doped with varying concentrations of Pb were prepared and systematically investigated to trace the effect of Pb doping on crystallization-induced phase transformations and thermoelectric properties. Via X-ray diffraction and Raman spectroscopy, the impact of Pb doping on the crystallization behavior was revealed and examined. According to the specific electrical resistivity measurements, the Pb doping resulted in decreasing both the amorphous-to-cubic and cubic-to-hexagonal transition temperatures, thereby facilitating the formation of the hexagonal phase at a lower thermal regime. Furthermore, Seebeck coefficient and electrical resistivity data of hexagonal Pb-doped GST were used to calculate the power factor, PF. A PF maximum equal to 1.3 was found for 2.5 at. Pb-GST at 633 K, with the highest carrier mobility also observed for this composition. Controlled Pb doping effectively modulates both structural transitions and thermoelectric performance, highlighting the potential of Pb-GST for applications that combine phase-change memory and thermoelectric functionality, such as opto-thermoelectric devices and non-volatile thermoelectric sensors.