Impact of the film thickness and substrate on the thermopower measurement of thermoelectric films by the potential-Seebeck microprobe (PSM). (25th August 2016)

• Record Type: Journal Article
• Authors: Zhou, Aijun; Wang, Weihang; Yao, Xu; Yang, Bin; Li, Jingze; Zhao, Qiang; Wang, Chao; Xu, Dongyan; Ziolkowski, Pawel; Mueller, Eckhard
• Is Part Of: Applied thermal engineering. Volume 107(2016:Aug.)
• Page Start: 552
• Page End: 559
• Publication Date: 2016-08-25
• Subjects: Thermopower -- Thermoelectric films -- Potential-Seebeck microprobe -- FEM simulation -- Substrate -- Film thickness; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2016.05.037
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: PSM is utilized to characterize the thermopower of thermoelectric thin/thick films. Measurement accuracy is highly dependent on film thickness and substrate. Larger thickness and higher substrate thermal conductivity improved the accuracy. FEM simulation is performed to reveal the origin of the PSM measurement deviation. Temperature/potential deviations and the eddy current effect are the main reasons. Abstract: Thermopower is a key parameter for thermoelectric (TE) materials. Compared to bulk materials, thermopower determination for TE films is challenging especially for those grown on electrically conductive substrates. This work demonstrates the feasibility of the on-substrate thermopower measurement for TE films by the unique potential-Seebeck microprobe (PSM). Thermopower measurements were conducted on the electroplated Bi2 Te3 films with different thicknesses prepared on Au-coated Si and quartz substrates in order to reveal the impact of the film thickness and substrate on the measurement accuracy. It is found that the thermopower ( S m ) measured on the Bi2 Te3 film grown on Si/Au substrates tends to deviate significantly from the real value if the thickness is smaller than 12 μm. Above 12 μm, no thickness dependence was observed and reliable S m can be obtained for the Bi2 Te3 films. Results on quartz/Au substrates show similar thickness dependence for S m, but the derived values are much lower than those obtained on Si/Au substrates. Finite element method (FEM) simulations are performed to interpret the measurement discrepancy as well as the impact of the film thickness and substrate on the thermopower measurement by investigating the detailed temperature and potential profiles in the samples.