Investigation of process parameter variation on properties of magnetron sputtered p-type Bi0.5Sb1.5Te3 thermoelectric thin films

Abstract

An investigation on the effects of process parameter variation of magnetron sputtering on the properties of p-type Bi0.5Sb1.5Te3 thin films was conducted in this study. Working pressure and gas flow, substrate temperature, and annealing were varied for a total of 8 samples. The composition, surface morphology, and, thermoelectric properties were evaluated using a combination of XRD, SEM, EDX, ZEM, and Hall Effect measurements. It was found that the equipment and methods employed were ineffective in determining conclusive trends for the parameter variations. Furthermore, the annealing method using the magnetron sputtering machine itself was inefficient and produced minor effects on the surface morphology and the crystallography of the materials. The composition of the materials was also found to be constantly deficient in Tellurium and process parameter variations did not significantly increase or reduce its deficiency. However, abnormally high Seebeck coefficient values (~300-650uV/K) which have not been reported before were discovered for the 30°C deposited samples. These Seebeck coefficient values appeared to be carrier mobility dependant and could have been caused by phonon assisted effects. Due to these high values, the highest power factor within this study was found to be 1.02mW/m K2 (590μV/K, 31.4mΩ cm) at 98°C. However, further investigation is necessary before any conclusions can be made regarding these effects.