Tunable optically transparent graphene–ITO patterning-based millimeter-wave absorber

In this work, we demonstrated a multilayer millimeter-wave absorber capable of tuning the absorption frequency while simultaneously maintaining the optical transparency. It comprises indium tin oxide (ITO) as the bottom ground plane deposited over polyvinyl chloride (PVC) substrate over which a patterned ITO layer is formed. Above this ITO layer, a PVC spacer is put to isolate the upper graphene sandwich structure (GSS) comprising of two patterned graphene mediums separated by a diaphragm paper. The configuration shows the tunability of reflectance minima (which correspond to high absorptance of ≥ 98 %) in a frequency range of 92.5–97.5 GHz due to the adjustable bias voltage applied to GSS. Additionally, the designed absorber demonstrates adequate shielding effect, generally required for both commercial and military applications in the stated frequency range. This simultaneously configurable and optically transparent device has potential in multispectral and smart stealth technologies, particularly 6G applications.