High Seebeck coefficient in PVD-WS2 film with grain size enlargement

A high Seebeck coefficient of 1.17 × 103 μV K−1 was achieved using an on-chip thermoelectric device for a WS2 atomic-layer film, which was synthesized by ultra-high vacuum RF magnetron sputtering as a function of sputtering power. A layered structure in parallel to the SiO2/Si substrate was confirmed from the transmission electron microscopy and X-ray diffraction spectra. The grain size and peak intensities of the Raman spectra increase with a decrease in the sputtering power. Accordingly, the resistivity and activation energy also increase. The WS2 film can be used in thermoelectric generators, such as energy harvesters in LSIs and wearable devices.