Seebeck coefficient of quasi-two-dimensional SnSxSe2−x crystals

Abstract

We have measured the Seebeck coefficient of quasi-two-dimensional single crystals of SnSe2, SnS0.1Se1.9, and SnS0.3Se1.7, grown by the Bridgman technique, and SnSe2, grown by iodine transport, over a large temperature range varying from 15 (4.2 for SnSe2) to 300 K. To assist in the interpretation of these results, the Hall coefficient and resistivity were measured on SnSe2 and SnS0.1Se1.9 Bridgman samples. All these measurements were done in a plane perpendicular to the c axis. It was found that, as the temperature decreases, the absolute value of the Seebeck coefficient decreases slightly before a surprisingly large increase at the lowest temperatures. We interpret these results as the manifestation of two conduction mechanisms: electrons in the conduction band and hopping of electrons between impurities.