Nanostructural effect on thermoelectric properties in Si films containing iron silicide nanodots

• Published in: Japanese Journal of Applied Physics 2020-04, Vol.59 (SF), p.SFFB01
• Main Authors: Sakane, Shunya, Ishibe, Takafumi, Taniguchi, Tatsuhiko, Hinakawa, Takahiro, Hosoda, Ryoya, Mizuta, Kosei, Alam, Md. Mahfuz, Sawano, Kentarou, Nakamura, Yoshiaki
• Format: Article
• Language: English
• Subjects: Crystal defects; Crystal structure; Crystallinity; Disilicides; Drawing and ironing; Heat conductivity; Heat transfer; Intermetallic compounds; Internet of Things; Iron silicide; Nanocomposites; Point defects; Power factor; Power management; Power sources; Silicon films; Size distribution; Thermal conductivity; Thermoelectric materials; Thin films
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/1347-4065/ab5b58

Thin film thermoelectric materials have drawn much attention for realizing one-chip stand-alone power sources of Internet of Things devices. Here, we fabricate two types of the nanostructured Si films with high crystallinity: Si films containing β-FeSi2 nanodots with a wider nanodot size distribution of ~5–120 nm and Si films containing α-FeSi2 nanodots with a narrow size distribution of ~5–20 nm. The thermal conductivity of these films is lower than those of Si–silicide nanocomposite bulks. Interestingly, Si films containing β-FeSi2 nanodots show about two times lower thermal conductivity than Si films containing α-FeSi2 nanodots. This is because the widely-size-distributed β-FeSi2 nanodots can effectively work as phonon scattering centers due to hierarchical architectures. These films also exhibited a high power factor due to the small amount of point defects and single crystalline epitaxial interfaces, regardless of the iron silicide phase of nanodots. These detailed investigations will open a road for realizing high-performance thin film thermoelectric materials.