(Invited) Advances in Testing Inorganic & Hybrid Organic Thermoelectric Thin Films

Abstract

In this work, a novel Si-based Lab-on-a-Chip test platform is introduced to perform in-plane ZT measurements of various classes of thermoelectric films with a complete set of thermoelectric test structures. The electrical conductivity σ, the Seebeck coefficient S, the thermal conductivity κ, and the power factor PF and the figure of merit ZT values can be experimentally determined in a single simultaneous measurement run as a function of temperature. It is shown that this Lab-on-a-Chip test system can be applied to classic inorganic thermoelectric films such as PbTe and PbSe and also to hybrid inorganic-organic films such as SURMOF films and as well as to conducting organic PEDOT:PSS films. Generally, the thermoelectric film can be deposited in the exposed test area of the chip by using a shadow mask. All the parameters can be measured in the temperature range of 300 K to 370 K with a 1 T magnet field. Applications are demonstrated for all three film material categories. Here, PbTe and PbSe thin films and double-layer PbTe/PbSe films were synthesized by Atomic Layer Deposition (ALD) technology directly on the pre-structured Si chip. A thin Al2O3 protection and diffusion barrier layer was applied to avoid oxidation and degradation of PbTe/PbSe films. The Seebeck coefficient, electrical conductivity and thermal conductivity for PbTe, PbSe and double-layer PbTe/PbSe film were measured simultaneously by applying in-pane ZT chips. Furthermore, this Lab-on-a-Chip test system can be extended to Surface Anchored Metal-organic-framework (SURMOF) films, which consist of quasi-liquid phase epitaxially grown highly ordered crystalline films. MOF films are designed scaffold-like compounds that consist of metal ions connected by organic ligands. Furthermore, the example of a complete thermoelectric characterization of a conductive organic polymer thin film material will be discussed.