Wafer-scale interface-clean few-layer graphene stacks enabled by active oxygen treatment

Interface quality, one of critical factors, governs the properties of few-layer graphene, which exhibit exclusive electrical and mechanical properties owing to the strong interlayer coupling. However, fabrication of interface-clean few-layer graphene still remains challenging. Conventional stacking techniques often introduce interfacial contamination, such as amorphous carbon and residual impurities, which critically deteriorate the interlayer coupling and compromise the uniformity and reliability of graphene-based devices. Here, we present an active oxygen treatment (AOT) strategy to effectively remove surface impurities and amorphous carbon on graphene before stacking, yielding wafer-scale few-layer graphene with clean interface and controlled layer numbers. As-fabricated few-layer graphene exhibits excellent structural integrity (>95%), flatness (R_a ~ 2.3 nm) and uniformity. The suspended few-layer graphene shows superior mechanical stability due to the clean interface, which remains stable under repeated thermal shocks up to 1200 K, significantly outperforming counterparts assembled via conventional methods. Thermal light emitters based on the suspended few-layer graphene demonstrates strong visible-to-near-infrared emission, with lattice temperature reaches ~900 K and a working lifetime of ~70 min. This work highlights the potential of AOT in advancing the optoelectronic applications of graphene through precise interface engineering.