Two-dimensional Janus transition metal dichalcogenides are a unique class of materials with broken inversion symmetry and an intrinsic electric field across the layer. In this thesis, we investigate RhSeCl, a newly synthesized Janus semiconductor with exceptionally low chalcogen mixing. Using angle-resolved photoemission spectroscopy (ARPES), we demonstrate termination-dependent electronic structures. We directly probe the intrinsic electric field in atomic-scale p–n junctions realized by encapsulating few-layer RhSeCl between monolayer graphene electrodes. In addition, we investigate the charge-density-wave system 1T-TaSe₂​. ARPES measurements reveal that charge transfer to the surrounding graphene/graphite environment suppresses the expected Mott insulating state in the monolayer limit. With increasing thickness, quantum well states emerge in few-layer 1T-TaSe₂​ due to out-of-plane confinement.