Layer by layer growth of Bi2Te3 epitaxial thermoelectric heterostructures

Epitaxial films of n- and p-type (0001)Bi₂Te₃ with carrier concentrations between 1×10¹⁸ and 8×10¹⁹ cm^-3 have been grown by hot wall epitaxy at the surface of mica. Granular textured films have been grown on barium fluoride substrates. A regular system of growth steps of 1 nm height was observed at the surface of the Bi₂ Te₃ films grown on mica at 600 K. The spirals (m≈10 ⁶ cm^-2) were detected by AFM at the surface of the thermoelectric films when substrate temperature was increased to 640 K. Steps at the surface of freshly cleaved BaF₂ substrate promote the formation of a grains in the Bi₂Te₃ film and rough surface. The α ²σ for the Bi₂ Te₃ films with electron and hole conductance at 300 K was in the range 40-60 μW cm^-1 K^-2