Effect of Working Pressure on the Structural and Thermoelectric Properties of Bismuth Telluride Thin Films Deposited by Magnetron Sputtering
Highly (00l)-oriented bismuth telluride polycrystalline thin films were prepared on quartz glass by magnetron co-sputtering at appropriate working pressure. The effect of working pressure on the growth behavior, microstructure and electrical transport properties of Bi2Te3 thin films were studied. The results showed that increasing working pressure brought more particle scattering and also decreased the velocity of the sputtered particles. As a result, the nucleation rate of the crystal grains decreased and more sufficient growth along the in-plane direction was induced. When the working pressure was 2.0 Pa, the balance between nucleation rate and growth rate of the crystal grains reached, which brings highly (00l) crystal plane orientation in Bi2Te3 polycrystalline thin film. Compared with the Bi2Te3 thin film with certain (015) orientation deposited at 0.5 Pa, the (00l)-oriented Bi2Te3 thin film had the double Seebeck coefficient, which was above −200 μV K−1 between 300 and 400 K and reached to the maximum value −225 μV K−1 at 360 K. Therefore the power factor of the thin film is greatly enhanced and reaches to above 38 × 10−4 W m−1 K−2 at 360 K, which is comparable to the value of the optimal Bi2Te2.7Se0.3 bulk alloys.
KeywordsBismuth telluride Thin film Magnetron sputtering Thermoelectric property
This work was supported by the State Key Program of National Natural Science Foundation of China (Grant No. 61534001) and National Natural Science Foundation of China (Grant No. 51601005)