Controllable Electrical Contact Resistance between Cu and Oriented-Bi2Te3 Film via Interface Tuning.

The contact resistance between metals and semiconductors has become critical for the design of thin-film thermoelectric devices with their continuous miniaturization. Herein, we report a novel interface tuning method to regulate the contact resistance at the Bi2Te3-Cu interface, and three Bi2Te3 films with different oriented microstructures are obtained. The lowest contact resistivity (∼10-7 Ω cm2) is observed between highly (00l) oriented Bi2Te3 and Cu film, nearly an order of magnitude lower than other orientations. This significant decrease of contact resistivity is attributed to the denser film connections, lower lattice misfit, larger effective conducting contact area, and smaller width of the surface depletion region. Meanwhile, our results show that the reduction of contact resistance has little dependence on the interfacial diffusion based on the little change in contact resistivity after the introduction of an effective Ti barrier layer. Our work provides a new idea for the mitigation of contact resistivity in thin-film thermoelectric devices and also gives certain guidance for the size design of the next-level miniaturized devices.