Compressive strain engineering in inclined SnSb2Te4 thin film for high-performance TTE photodetection

Abstract

Self-powered photodetectors based on the transverse thermoelectric (TTE) effect have attracted significant attentions due to their ultrasensitive detection and sub-100-ns-level response speeds. However, achieving practically viable detection sensitivity remains a critical challenge in this emerging field. Here, we propose a substrate-induced-compressive strain strategy to enhance the TTE performance in c-axis inclined SnSb₂Te₄ thin films. Through systematic investigation of three lattice-mismatched substrates (MgO, SrTiO₃, and LaAlO₃), the controlled strains (up to 12 % for LaAlO₃) enhance electrical conductivity, suppress thermal conductivity, and amplify Seebeck coefficient anisotropy. This synergistic optimization enables superior TTE detection performance under 308 nm UV pulsed laser irradiation, whose record-high sensitivity is 20.5 V/mJ, ultrafast response time is 73 ns and exceptional figure of merit (F_m) is 566 mV/ns. Our findings not only position SnSb₂Te₄ as a prime candidate for weak-signal UV photodetection but also establish substrate-induced-compressive strain as a universal strategy for developing high-sensitivity and fast-response TTE photodetectors.