Reactivity-Guided Janus Graphene With Asymmetric Interfacial Electrostatics for Tunable Charge Transport

Breaking out-of-plane symmetry in graphene is essential to realize electrostatic control in next-generation electronic devices. While Janus graphene, which bears chemically distinct top and bottom faces, is a promising architecture, establishing a controllable fabrication route and directly linking asymmetric chemistry to electronic transport remains challenging. In this study, we present a resist-free, interface-selective laser-writing strategy that facilitates stepwise bottom-to-top covalent functionalization of graphene and enables controlled access to top-, bottom-, and asymmetric dual-side configurations. Raman spectroscopy verifies that this Janus configuration reaches a substantial degree of functionalization, exhibiting a Raman-derived defect distance (L_D) of approximately 1.5 nm. Kelvin probe force microscopy reveals configuration-dependent electrostatic responses, with a change of contact potential difference of approximately 225 mV for Janus graphene. Back-gated field-effect transistors further reveal pronounced changes in charge transport, with the residual carrier density increasing to 5.92 × 10¹² cm^-2 in Janus graphene. Notably, comparison of the investigated configurations reveals a configuration-dependent relationship between interfacial electrostatics and charge transport. Furthermore, lithographically pre-patterned substrates enable spatially programmable Janus architectures via single-step laser writing, providing a scalable platform for engineering symmetry-broken two-dimensional electronic materials.