Abstract
The primary objective of this thesis was to establish a robust and reproducible experimental framework for the fabrication of ultra-clean two-dimensional (2D) van der Waals heterostructures, specifically optimized for high-fidelity scanning tunneling microscopy (STM) and spectroscopy (STS) investigations. While the field of moiré quantum matter has expanded rapidly, the extreme sensitivity of the STM probe to surface residues remains a formidable bottleneck. Achieving an atomically pristine interface is not merely a technical requirement but a fundamental prerequisite for uncovering intrinsic many-body phenomena that are otherwise obscured by disorder.
In this work, we have successfully achieved this objective by developing an integrated fabrication and cleaning pipeline. A cornerstone of this achievement is the realization of super large, residue-free surfaces with pristine areas extending over hundreds of nanometers (typically > 100×100 nm2). By implementing a specialized combined PC and PVA transfer process and contact-mode AFM mechanical sweeping, we obtained a sub-angstrom surface roughness (Rq ≈ 0.04 nm), providing an ideal platform for local spectroscopic probes.
Building upon this established fabrication excellence, this thesis presents preliminary but significant spectroscopic data on two frontier physics topics. We explore the gate-tunable Kondo effect of Dirac particles by depositing magnetic adatoms on ultra-clean graphene. Subsequently, we investigate the emergent correlated electronic states in magic-angle twisted bilayer graphene (MATBG), where we resolve interaction-driven spectral reconstructions and van Hove singularity splitting at specific moiré filling factors.