Imaging and Probing Point Defects in Gate-Tunable Two-Dimensional Semiconductors via Scanning Tunneling Microscopy

With the recent advances in two-dimensional (2D) materials, semiconducting 2D transition metal dichalcogenides (TMDs) have shown potential as the next generation nanoelectronics to keep up with Moore’s law. Since the performance of semiconductor devices can be greatly affected by defects and gating, the ability to control defects in these 2D materials in a gate tunable device becomes vital. The species and density of defects depend on the growth method as well as the postgrowth device fabrication processes. In this talk, I will present atomically resolved images of the defects and show how their local electronic properties are modulated by the application of a gate electric field. Chemical vapor deposition (CVD) is used in this study to reliably produce 2D TMD monolayers while allowing for defect engineering. We use a low-temperature scanning tunneling microscope (STM) to study the point defects in a CVD-grown 2D TMD monolayer that is implemented in a heterostructure with gate tunability. First, the identification of the defects is realized by combining scanning probe microscopy with density functional theory (DFT) calculations. Next, the effect of a gate electric field is explored and compared to DFT modeling. Our results will provide guidance on future defect engineering in gate-tunable 2D TMD based devices.<br/><br/>This research is supported by the Gordon and Betty Moore Foundation award #10.37807/GBMF11569.