Microstructure and thermoelectric properties of p-type Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.7Se_0.3 films deposited by pulsed laser ablation

Thin films of p-type Bi_0.5Sb_1.5Te₃, n-type Bi₂Te_2.7Se_0.3 and n-type with SbI₃ doping were deposited on mica substrates using Nd-YAG pulsed laser ablation at temperatures ranging from 300°C to 500°C. These films were characterized using X-ray diffraction, SEM and TEM. X-ray mapping and EDS were used to determine the composition. The films showed uniform thickness and high crystalline quality with a preferred (00n) alignment with the substrates. The film quality in terms of composition and crystal perfection is studied as a function of growth temperature. It was found that films deposited at 350°C gave improved crystallinity and thermoelectric characteristics. The Seebeck coefficient, electrical resistivity and Hall mobility were measured as a function of temperature and compared with the measurements on the bulk. Correlation of thermoelectric properties with microstructure is discussed.