Photo-thermoelectric properties of SnS nanocrystals with orthorhombic layered structure

Abstract

The photo-thermoelectric properties of SnS nanocrystals, two-dimensional materials with an orthorhombic symmetry, were investigated using a focused laser scanning method. The SnS nanocrystals were synthesized by a vapor transport method, and their fundamental material and electrical properties were investigated. Upon shining a laser onto the SnS channel region under a positive source-drain bias, a positive photocurrent was observed due to photo-excited electron-hole pairs. On the other hand, when this external electric field was not applied, a strong photocurrent was observed within the metal electrode region rather than at the metal-semiconductor interface, which indicated that the major mechanism for the photocurrent under zero external bias was a photo-induced thermoelectric effect rather than a photovoltaic effect. Moreover, the Seebeck coefficient of the SnS nanocrystal device was approximately 1735 μV/K, which is 3.5 times larger than that of its bulk counterpart.

Synthesis of Bi2Te3 Single Crystals with Lateral Size up to Tens of Micrometers by Vapor Transport and Its Potential for Thermoelectric Applications

“…In particular, a photovoltaic current is observed mainly when light is focused at the interface of the metal−semiconductor contact with a Schottky barrier, while the photo-thermoelectric current, originating from a temperature gradient by photon absorption, can be observed when the light is irradiated inside the metal electrodes. 12,14 For the Bi 2 Te 3 device, as shown in Figure 5c, considerable photocurrents of 0.157 and 0.091 nA for the source and drain, respectively, were observed within the metal electrode region. Therefore, it is believed that the photothermoelectric effect was the main mechanism for the photocurrent generated at V SD = 0 V. The source/drain metal contact region was defined using a recorded reflection image of the device (inset in Figure 5c).…”

“…Among the various types of two-dimensional (2D) layered crystals, bismuth telluride (Bi 2 Te 3 ) is one of the most promising with a narrow bandgap owing to its unique physical properties as a topological insulator , and superior properties as a thermoelectric material. − In particular, owing to its relatively low thermal conductivity and high electrical conductivity, various types of Bi 2 Te 3 crystals, such as thin films, , nanowires, , and nanocrystals, have been actively investigated for application to thermoelectric devices. In addition, in recent years, the photo-thermoelectric effect in 2D layered materials has attracted significant attention, owing to its potential applicability to next-generation nanoscale thermoelectric devices. − For the investigation of the photo-thermoelectric effect in layered crystals, it is important to obtain high-quality single crystals with a minimum lateral size of several tens of micrometers. Chemical vapor synthesis is one of the most suitable processes to synthesize high-quality 2D layered single crystals.…”