Potential-current co-adjusted pulse electrodeposition for highly (110)-oriented Bi2Te3-xSex films

Abstract

Controllable crystal orientation is necessary to obtain high thermoelectric performance in thin films of Bi2Te3 alloys. In the present study, highly (110)-oriented thin films of n-type Bi2Te3-xSex with improved composition controllability are prepared through a simple electrodeposition-based process. Using potential-current co-adjusted pulse electrodeposition (PCP-ED) with adjustments to the zero current during the off-time period enables the fabrication of dense Bi2Te3-xSex thin films with highly (110)-oriented grains by minimizing the ionic gradient (Bi3+, Te2-, Se2-) between the substrate and solution. The power factor of the PCP-ED thin film was much higher than that of the dendritic Bi2Te3-xSex thin film fabricated by constant-potentiostatic electrodeposition (C-ED) because of the simultaneous enhancement of electrical conductivity and Seebeck coefficient. The high power factor of similar to 1920 mu W/m.K-2, which is the best value among reported n-type Bi2Te3-based thin films, was obtained at room temperature after low-temperature annealing at 200 degrees C by exploiting the crystallinity enhancement and carrier concentration optimization. (C) 2019 Elsevier B.V. All rights reserved.