HWE法により成長させたBi₂Te₃単結晶薄膜の結晶評価と熱電特性

抄録

Thin films of Bi₂Te₃ were grown on mica (001) substrates by hot wall epitaxy (HWE). Reflection high energy electron diffraction (RHEED) patterns of deposited films indicated that the film condition depends on the substrate temperature in the film growth process, and the epitaxial Bi₂Te₃ single crystal films were grown with two-steps substrate temperature control. The X-ray diffraction (XRD) pattern indicated that the Bi₂Te₃(0001) single crystal film was grown on the mica substrate with c-axis oriented perpendicular to the substrate plane. The microstructure of the Bi₂Te₃ film was examined by scanning electron microscope (SEM), and the layered structure was observed. The deviation from stoichiometric composition causes the change in the conduction character, the film with an excess of tellurium is n-type and with an excess of bismuth is p-type. Hall concentrations for n- and p-type films were 2.4×10²⁵/m³ and 3.1×10²⁵/m³ respectively: The Seebeck coefficient α and the power factor α2/ρ for n-type film were -237μV/K and 2.6×10^-3W/(K²m) at 293K, and those for p-type, 141μV/K and 0.55×10^-3W/(K²m).