Oxidation-induced thermopower inversion in nanocrystalline SnSe thin film

Abstract

Given the growing demand for environmentally friendly energy sources, thermoelectric energy conversion has attracted increased interest as a promising CO2-free technology. SnSe single crystals have attracted attention as a next generation thermoelectric material due to outstanding thermoelectric properties arising from ultralow thermal conductivity. For practical applications, on the other hand, polycrystalline SnSe should be also focused because the production cost and the flexibility for applications are important factors, which requires the systematic investigation of the stability of thermoelectric performance under a pseudo operating environment. Here, we report that the physical properties of SnSe crystals with nano to submicron scale are drastically modified by atmospheric annealing. We measured the Seebeck effect while changing the annealing time and found that the large positive thermopower, + 757 μV K−1, was completely suppressed by annealing for only a few minutes and was eventually inverted to be the large negative value, − 427 μV K−1. This result would further accelerate intensive studies on SnSe nanostructures, especially focusing on the realistic device structures and sealing technologies for energy harvesting applications.

Recent Advances in SnSe Nanostructures beyond Thermoelectricity

“…Shimizu et al. [ 132 ] found that the thermopower of SnSe was inverted after long atmospheric annealing at ≈480 K due to surface oxidation. In addition, the resistance of the sample reduces with increasing annealing time.…”

“…Zhong et al [131] showed that SnSe NSs could completely transform into SnO 2-x NSs after 1 h annealing at 500 °C. Shimizu et al [132] found that the thermopower of SnSe was inverted after long atmospheric annealing at ≈480 K due to surface oxidation. In addition, the resistance of the sample reduces with increasing annealing time.…”

Physics and technology of thermoelectric materials and devices

“…The Seebeck coefficient changed its polarity with the annealing for different time duration. The freshly deposited SnSe thin films had a S value of +757 µVK −1 , which changed to −427 µVK −1 for the films annealed for 11,500 min in the air [234]. The thermoelectric transport of thin films is influenced by various parameters such as deposition time [235], deposition temperature [236], distance between the target to the substrate as well as annealing time and temperature [237,238].…”

Characterization of tin selenide nanoparticle films generating from plasma arc penetration of a temperature-varying field

“…From the Figure 4(a), it is noticeable that the absorption coefficient (α) increases as the T p-f increases, and its value for all the obtained thin films is larger than (10 4 ), which indicates the direct transition of electrons. Tauc's relation [27] was applied to determine the optical band gap energy for the SnSe thin films:…”