  Two-dimensional atomic crystals (2DACs) can be mechanically assembled with
precision for the fabrication of heterostructures, allowing for the combination
of material building blocks with great flexibility. In addition, while
conventional nanolithography can be detrimental to most of the 2DACs which are
not sufficiently inert, mechanical assembly potentially minimizes the
nanofabrication processing and preserves the intrinsic physical properties of
the 2DACs. In this work we study the interfacial charge transport between
various 2DACs and electrical contacts, by fabricating and characterizing
2DAC-superconductor junctions through mechanical transfer. Compared to devices
fabricated with conventional nanolithography, mechanically assembled devices
show comparable or better interface transparency. Surface roughness at the
electrical contacts is identified to be a major limitation to the interface
quality.
