A new class of thermoelectric thin films using gradient doping has been introduced and investigated. Films were fabricated using Direct Current (DC) Magnetron Sputter deposition with Tin (Sn) strips, of low thickness, physically attached to a Bi2Te2.7Se0.3 sputtering target. This novel method is quicker, more economical and more environmentally friendly compared to using several targets of different compositions. Firstly, an approximately linear increase in Sn content was observed: x ~ 0, x ~ 0.25, x ~ 0.58, and x ~ 0.73 with the addition of zero, one, two and three Sn strips to fabricate each of the four Bi2-xSnxTe2.7Se0.3 films respectively.From resistivity (?) and Seebeck Coefficient (a) measurements obtained by ZEM-3, x ~ 0.58 proved to be optimal amongst the four films. Next, cross-plane gradient Sn doped films were successfully fabricated with four layers of increasing Sn dopant concentration (zero to three Sn strips). The gradient-doped film yielded significantly lower resistivities than conventional undoped and Sn-doped Bi2Te2.7Se0.3 films, as well as comparable Seebeck Coefficients. Thus, the overall Power Factor (a2?-1) values of the gradient Sn-doped films (92�W/cm K2) showed a threefold increase compared to conventional doped and undoped films, revealing the immense potential of gradient doping in thin films to harvest electrical energy from waste heat moreeffectively for green technology applications. Behavior of Sn dopants in this novel gradient dopant design was also studied via Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) characterization methods.

Enhanced thermoelectric performance in gradient Sn-doped Bi2Te2.7Se0.3 thin films deposited by DC sputtering

247th National Meeting (2014)

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