Tunneling spectroscopy of VOPc encapsulated in Van der Waals heterostructures

Small molecules have gained recent interest as qubit candidates due to their tunability via chemical modification. Molecular qubits have been studied extensively optically but electrical studies are hampered by the lack of a robust mechanism for integration into a solid-state architecture. In this work, we present a method for encapsulating small molecules, vanadyl phthalocyanine (VOPc), into a mechanically exfoliated heterostructure to generate a graphite/hBN /VOPc/hBN/graphite tunnel junction and probe the electronic states of the molecule via tunneling spectroscopy. We observe resonances in the tunneling spectra of these devices that quantitatively agree with spectra obtained via scanning tunneling microscopy (STM) of graphite/hBN/VOPc half-stacks. This result paves the way for further studies of the electrical and spin properties of many a wide variety of molecules, adatoms, and point defects encapsulated in 2D tunnel junctions.