Scanning Tunneling Microscopy Characterization of Intrinsic Point Defects and Their Local Density of States in α-In₂Se₃.

Abstract

Two-dimensional ferroelectric materials exhibit great potential for high-performance electronic devices. However, the impact of defects on the electronic behavior remains unclear. Here, we systematically characterized intrinsic point defects in bulk α-In₂Se₃, focusing on topographic configurations and localized electronic states, using high-resolution scanning tunneling microscopy and spectroscopy. Combined with first-principles calculations, we reveal that the defects in α-In₂Se₃ arise surprisingly from single indium vacancies instead of chalcogen vacancies that prevail in transition metal dichalcogenides. Additionally, we identify indium antisite defects as another common defect type. The scanning tunneling spectroscopy measurements further reveal that indium vacancies induce <i>p</i>-doping, whereas the indium antisite provide complementary <i>n-</i>doping, confirmed by first-principles calculations. Notably these defects induce bipolar doping in α-In₂Se₃ despite the intrinsic <i>n</i>-type character. Finally, this research fills the gap resulting from the absence of sufficient experimental data on the intrinsic defects in α-In₂Se₃ and provides critical insights for future design of In₂Se₃-based devices.