ATOMIC DEFECTS CHARACTERIZATION AND ENGINEERING IN 2D SEMICONDUCTORS BY STM/NC-AFM

Abstract

Defects play an essential role in modulating the optical and electronic properties of two-dimensional (2D) semiconductors. Understanding the structure-property correlation of atomic defects in 2D semiconductors has significant fundamental interest and technological impact. In this thesis, we focus on the investigation of structural and electronic properties of atomic defects in 2D semiconductors using a joint low temperature (LT) scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM), corroborated by density functional theory (DFT) calculations. Firstly, we demonstrated an ionization-induced self-electronic passivation over single vacancy in black phosphorus (BP), which can be controlled by thermal annealing or STM tip manipulation. Next, we investigated the geometrically dependent electronic properties of atomically-precise vacancy clusters in platinum ditelluride (PtTe2) triggered by a controllable thermal annealing. Lastly, we focused on the study of self-depolarization induced surface reconstruction in alpha-phase indium selenide (α-In2Se3) with tunable local electronic properties. These findings enrich the atomic-level understanding of the impact of atomic defects on the electronic properties of 2D semiconductors, which may govern their transport characteristics in nanodevices.