Potential-current co-adjusted pulse electrodeposition for highly (110)-oriented Bi₂Te_3-xSe_x films

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 Bi₂Te_3-xSe_x 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 Bi₂Te_3-xSe_x 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 Bi₂Te_3-xSe_x 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 ∼1920 μW/m⋅K², which is the best value among reported n-type Bi₂Te₃-based thin films, was obtained at room temperature after low-temperature annealing at 200 °C by exploiting the crystallinity enhancement and carrier concentration optimization.