Graphene–oxide heterostructures have become important for studying interfacial polarisation and creating electrically tunable features in two-dimensional devices. This study uses first-principle calculations to examine how an external electric field affects the surface polarisation of a graphene/SrTiO₃ heterostructure. Using density functional theory (DFT) and a slab model, the interaction between a graphene layer and a TiO₂-terminated SrTiO₃ surface has been studied. The goal was to understand the microscopic processes behind charge redistribution and polarisation at the interface. To understand how they affect electronic structure, charge transfer, and polarisation, the direction and strength of an electric field applied perpendicular to the heterostructure are systematically changed. The results show that adding graphene significantly changes the surface electronic properties of SrTiO₃. This change is due to the redistribution of charges at the interface and screening effects. When an external electric field is applied, the charge density distribution becomes noticeably asymmetric. This creates a surface polarisation that can be adjusted, with its size and direction strongly depending on the direction of the field. Positive and negative bias fields are found to enhance or suppress polarisation through distinct charge accumulation and depletion mechanisms at the graphene–oxide interface. Moreover, changes in the band alignment caused by the field suggest that it can be controlled the electronic properties at the interface without using chemical doping. The findings suggest that external electric fields offer a useful way to dynamically control surface polarisation in graphene/SrTiO₃ heterostructures. The present study offers fundamental insights into electro-field-driven polarisation control and establishes a theoretical framework for designing graphene-based field-effect devices and oxide electronics with electrically switchable functionalities.

Keywords: Graphene/SrTiO₃ Heterostructure; Density Functional Theory; Surface Polarization; Electric Field Effect; Interfacial Charge Transfer;