Thickness-dependent thermoelectric characterization of 2D SnSe2 on a micro-chip platform

Abstract

Investigating the temperature dependence of the Seebeck coefficient in low-dimensional materials provides an effective means to uncover how crystallinity, size, and thickness influence thermoelectric performance. Such insights are crucial for advancing large-scale thermoelectric devices and Seebeck-based sensors. To enhance measurement precision and efficiency, we developed a microchip platform specifically tailored for accurate Seebeck coefficient measurements in low-dimensional systems. The chip accommodates a broad range of samples, including both polycrystalline thin films (chemically or physically deposited) and mechanically exfoliated two-dimensional (2D) crystals. It integrates micro-heaters, temperature sensors, and voltage electrodes, enabling the generation of controlled in-plane temperature gradients and the simultaneous measurement of the induced Seebeck voltage (ΔV). Finite-element simulations support the formation of stable and tunable temperature differences across the chip. To validate the platform, we first measured Bi2Te3-based thin films, obtaining Seebeck coefficients consistent with reported literature values, thereby confirming the accuracy and robustness of the setup. Subsequently, mechanically exfoliated crystalline SnSe2 flakes were investigated. Their Seebeck coefficient exhibited clear dependencies on both thickness and temperature, the absolute value increasing from −349 ± 20 μV/K at 100 K to −521 ± 10 μV/K at 300 K in a 198 nm-thick sample. These findings highlight the strong influence of dimensionality on thermoelectric transport in SnSe2. Overall, this work establishes a versatile platform for evaluating emerging 2D materials and their heterostructures, facilitating both fundamental research and the engineering of efficient 2D material-based thermoelectric devices.