Enhanced thermoelectric properties of Ge2Sb2Te5 thin films through the control of crystal structure

Tuning the structure and chemical composition of 0.3 μm-thick Ge2Sb2Te5 (GST) films via control of the deposition temperature enhanced thermoelectric performance by balancing the Seebeck coefficient, the electrical conductivity, and the thermal conductivity. By combining the phases of the face-centered cubic (FCC) and hexagonal close packed (HCP) crystal structures of GST thin films deposited at 250 °C, a compromise was attained between a moderate degree of electrical conductivity and the Seebeck coefficient, which resulted in the highest power factor at 1.1 × 10−3 W/K2m. This was attributed to variations in the effective mass, the mixed crystal structure, and the chemical composition with deposition temperature. The highest maximum powers of 0.3 μm- and 1.0 μm-thick n-Bi2Te3 (BT) and p-GST thermoelectric generators with 5 p/n couples were approximately 4.1 and 52.9 nW at ΔT = 12 K, respectively. They showed higher maximum powers than those of referenced n-BT and p-Bi0.5Sb1.5Te3 (BST) thermoelectric generators.