Epitaxial tin selenide thin film thermoelectrics

To enable the realization of miniaturized thermoelectric energy generation (TEG) devices for autonomous wireless sensors, high-quality thin film architectures are required. Although tin selenide (SnSe) has been iden-tified as a promising thermoelectric material exhibiting ZT values up to 2.6 at 923 K for single crystals, most thin film studies evaluated polycrystalline or textured SnSe samples. Here, we have explored for the first time the impact of epitaxial alignment of the orthorhombic SnSe crystal structure on an orthorhombic DyScO3 substrate, in strong contrast to the few previous studies on cubic substrates. The achieved (100)-oriented single crystalline SnSe thin films exhibit the formation of two SnSe domain types. The in-plane electrical conductivity along the (b, c)-plane shows an abrupt increase above 400 K instead of the typical steady increase. The in-plane Seebeck coefficients exhibit very similar values as single crystals, leading to a maximum power factor of about 6.0 mu W.K-2.cm(-1). For these SnSe thin films, exhibiting two domain variants with in-plane alignment of the (b,c)-plane, a typical low thermal conductivity is expected, demonstrating the effectiveness of epitaxial alignment to enhance thermoelectric performance and to enable the realization of miniaturized thermoelectric energy gen-eration (TEG) devices for autonomous wireless sensors.

Automated summary

To enable miniaturized thermoelectric energy generation devices for wireless sensors, high-quality thin film architectures are needed. This study explores the impact of epitaxial alignment between the orthorhombic SnSe crystal structure and the orthorhombic DyScO3 substrate. The achieved (100)-oriented single crystalline SnSe thin films exhibit the formation of two domain types, and show a sudden increase in electrical conductivity above 400 K. The epitaxial alignment enhances thermoelectric performance and enables the realization of miniaturized TEG devices.