Proximity to Tunneling crossover in van der Waals semiconductor Josephson junctions*

 Van der Waals heterostructures serve as versatile platforms for exploring diverse physical phenomena and practical applications. In this study, we delve into the superconducting proximity effect within NbSe₂/WSe₂/NbSe₂ Josephson junctions, where the WSe₂ semiconducting weak links vary in thickness from 3 to 18 layers. By systematically increasing the thickness of WSe₂, we identify a crossover from proximity- to tunneling-type junction around 8 layers thick, indicating a proximity effect from the superconducting NbSe₂ extends approximately 4 layers deep into the WSe₂. We substantiate this discovery through an in-depth analysis of temperature-dependent junction return currents. Furthermore, our findings are corroborated by studying the I-V characteristics, size of the induced energy gap, and IcRN products. Our results provide valuable insights into the interfacial physics and proximity effects in van der Waals material-based Josephson junctions, offering a methodology that can be applied to explore similar effects in other van der Waals heterostructures