Lithographically Controlled Liquid Metal Diffusion in Graphene: Fabrication and Magnetotransport Signatures of Superconductivity.

Metal intercalation in epitaxial graphene enables the emergence of proximity-induced superconductivity and modified quantum transport properties. However, systematic transport studies of intercalated graphene have been hindered by challenges in device fabrication, including processing-induced deintercalation and instability under standard lithographic techniques. Here, a lithographically controlled intercalation approach is introduced that enables the scalable fabrication of gallium-intercalated quasi-freestanding bilayer graphene (QFBLG) Hall bar devices. By integrating lithographic structuring with subsequent intercalation through dedicated intercalation channels, this method ensures precise control over metal incorporation while preserving device integrity. Magnetotransport measurements reveal superconductivity with a critical temperature T c onset $T_c^{{\mathrm{onset}}}$ ≈ 3.5 K and the occurrence of a transverse resistance, including both symmetric and antisymmetric field components, which is attributed to the symmetric-in-field component of non-uniform currents. These results establish an advanced fabrication method for intercalated graphene devices, providing access to systematic investigations of confined 2D superconductivity and emergent electronic phases in van der Waals heterostructures.