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 (V-Sn) and negatively charged Sn interstitials (Sn-i) are the leading native atomic defects that dominate electronic transport in SnTe, in contrast to previous studies that only considered V-Sn. Increasing the substrate temperature (T-sub) and decreasing the Te/Sn flux ratio during film growth reduces the density of V-Sn while increasing the density of Sni. A high T-sub results in a low hole density and high carrier mobility in SnTe films. The SnTe film grown at T-sub = 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 x 10(20) cm(-3) and the increased carrier mobility of 85.6 cm(2) 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.

Automated summary

This study visualizes the dominant native atomic defects in SnTe and clarifies an alternative optimization mechanism for the electronic transport properties through defect engineering. Increasing substrate temperature and adjusting the Te/Sn flux ratio during film growth can manipulate the hole density and carrier mobility in SnTe films, leading to an improved power factor. The findings contribute to a better understanding of the electronic transport properties in SnTe-based compounds.