[8p-E203-1~15] 9.4 Thermoelectric conversion

4:45 PM - 5:00 PM JST(7:45 AM - 8:00 AM UTC)English Presentation

[8p-E203-13] A Hybrid AC–DC Seebeck Coefficient Measurement for Temperature Sensitive Thermoelectric Thin Films

〇(M2)Jiayi Zhang¹, Yujiao Zhou¹, Laurent Jalabert¹, Weitao Wang¹, Masahiro Nomura¹ (1.IIS, Univ. of Tokyo)

Keywords:

Seebeck coefficient,AC-DC Measurement

The Seebeck coefficient is a key parameter for evaluating thermoelectric materials, but its accurate measurement in thin-film structures is difficult because the thermoelectric voltage is small and easily affected by DC offsets, leakage currents, and low-frequency drift. Here, we demonstrate a hybrid AC–DC Seebeck measurement method based on the 3ω technique for n-type silicon-on-insulator (SOI) thin films under ultra-small temperature differences of approximately 0.1 K. Conventional DC-heating/DC-voltage measurements often require a relatively large temperature difference to obtain a detectable voltage. Since the Seebeck coefficient depends on temperature, this can result in averaging over a finite temperature range. In contrast, our method uses AC Joule heating at frequency ω to generate a 2ω temperature oscillation, and the corresponding Seebeck voltage is detected at 2ω. This frequency-domain detection suppresses DC parasitic signals and drift, enabling more local and sensitive evaluation of the temperature-dependent Seebeck coefficient. The temperature difference between voltage probes was evaluated using a thermal model with experimentally determined anisotropic thermal conductivities. We measured heavily doped n-type SOI thin films with different Si thicknesses and an average carrier concentration of approximately 3.2 × 10²⁰ cm^-3 from 300 to 400 K. The 220 nm film showed an 18% variation in the Seebeck coefficient within a 20 K interval, resolved with propagated error bars. The relatively smaller Seebeck coefficient in other thickness Si film could be related to a size-dependent phonon-drag contribution. These results demonstrate the capability of the hybrid AC–DC 2ω method for Seebeck characterization of temperature-sensitive thermoelectric films.