Realizing high thermoelectric power factor and stability of AlSnTe2 alloy thin film

Abstract

This study investigates the thermoelectric properties of AlSnTe₂ thin films, emphasizing the impact of post-annealing treatments on enhancing the thermoelectric power factor (PF) and overall stability. Scanning electron microscopy (SEM) analysis reveals that the as-grown films feature a smooth surface with large grains up to 1.76 μm in size. Post-annealing for durations of 1 to 3 h resulted in a significant transformation in the grain structure, with the most notable changes occurring after 3 h, where larger grains transitioned to smaller, metallic-like grains. The electrical conductivity increased from 388 S/cm in the as-grown sample to 432 S/cm following 3 h of annealing, attributed to improved grain connectivity and reduced scattering centers. Concurrently, the charge carrier concentration rose significantly from 1.05 × 10²⁰ cm⁻³ to 2.59 × 10²⁰ cm⁻³, driven by the formation of conductive secondary phases that minimized defect density. However, charge carrier mobility decreased from 21.05 cm²V⁻¹ s⁻¹ to 12.02 cm²V⁻¹ s⁻¹ due to increased carrier-carrier scattering at higher concentrations. The Seebeck coefficient exhibited n-type behavior, with values increasing from 128 μV/K to 171 μV/K as temperature rose from 300 K to 450 K. The maximum power factor of 10.29 μWcm⁻¹ K⁻² was achieved in the sample post-annealed for one hour at 450 K, demonstrating a balance between the Seebeck coefficient and electrical conductivity. These findings underscore the potential of AlSnTe₂ alloys for thermoelectric applications, highlighting the critical role of post-annealing in optimizing performance.