Native Atomic Defects Manipulation for Enhancing the Electronic Transport Properties of Epitaxial SnTe Films.

P-type SnTe-based compounds have attracted extensive attention because of their high thermoelectric performance. Previous studies have made tremendous efforts to investigate native atomic defects in SnTe-based compounds, but there has been no direct experimental evidence so far. On the basis of MBE, STM, ARPES, DFT calculations, and transport measurements, this work directly visualizes the dominant native atomic defects and clarifies an alternative optimization mechanism of electronic transport properties via defect engineering in epitaxially grown SnTe (111) films. Our findings prove that positively charged Sn vacancies (VSn) and negatively charged Sn interstitials (Sni) are the leading native atomic defects that dominate electronic transport in SnTe, in contrast to previous studies that only considered VSn. Increasing the substrate temperature (Tsub) and decreasing the Te/Sn flux ratio during film growth reduces the density of VSn while increasing the density of Sni. A high Tsub results in a low hole density and high carrier mobility in SnTe films. The SnTe film grown at Tsub = 593 K and Te/Sn = 2/1 achieves its highest power factor of 1.73 mW m-1 K-2 at 673 K, which is attributed to the optimized hole density of 2.27 × 1020 cm-3 and the increased carrier mobility of 85.6 cm2 V-1 s-1. Our experimental studies on the manipulation of native atomic defects can contribute to an increased understanding of the electronic transport properties of SnTe-based compounds.