Electrodeposited Thin-Film Micro-Thermoelectric Coolers with Extreme Heat Flux Handling and Microsecond Time Response.

Thin-film thermoelectric coolers are emerging as a viable option for the on-chip temperature management of electronic and photonic integrated circuits. In this work, we demonstrate the record heat flux handling capability of electrodeposited Bi2Te3 films of 720(±60) W cm-2 at room temperature, achieved by careful control of the contact interfaces to reduce contact resistance. The characteristic parameters of a single leg thin-film devices were measured in situ, giving a Seebeck coefficient of S = -121(±6) µV K-1, thermal conductivity of κ = 0.85(±0.08) W m-1 K-1, electrical conductivity of σ = 5.2(±0.32) × 104 S m-1, and electrical contact resistivity of ∼10-11 Ω m2. These thermoelectric parameters lead to a material ZT = 0.26(±0.04), which, for our device structure, allowed a net cooling of ΔTmax = 4.4(±0.12) K. A response time of τ = 20 µs was measured experimentally. This work shows that with the correct treatment of contact interfaces, electrodeposited thin-film thermoelectrics can compete with more complicated and expensive technologies such as metal organic chemical vapor deposition (MOCVD) multilayers.

Amorphous Framework in Electrodeposited CuBiTe Thermoelectric Thin Films with High Room-Temperature Performance.

Bismuth telluride-based alloys are the most efficient thermoelectric materials near room temperature and widely used in commercial thermoelectric devices. Nevertheless, their thermoelectric performance needs to be improved further for wide-scale implementation either as a thermoelectric generator or cooler. Here, we propose a simultaneous codeposition of CuBiTe thin films and their phase transition strategy via the traditional electrodeposition process. With just 13 atom % Cu doping, crystalline-to-amorphous phase transformation resulted for the electroplated CuBiTe alloy. A close look at the alloy composition revealed spike-shaped nanocrystalline Bi2Te3 embedded in the CuBiTe amorphous matrix. Our result shows an exceptionally high power factor (3.02 mW m-1 K-2), which comes from the enhanced Seebeck coefficient (-275 µV K-1) and high electrical conductivity (3.99 × 104 S m-1) of CuBiTe films. Therefore, it can be suggested that the adopted strategy to form a unique nanocrystallite-embedded amorphous framework provides a platform to develop next-generation high-performance thermoelectric materials with an extraordinary power factor.