Plasma-etching on monolithic MOFs-based MIM filter boosted chemical sensing

Metal-insulator-metal (MIM) cavity as a lithography-free structure to control light transmission and reflection has great potential in the field of optical sensing. However, the dense top metal layer of the MIM prohibits any external medium from entering the dielectric insulation layer, which limits the application of the cavity in the sensing field. Herein, we demonstrate a series of monolithic metal-organic frameworks (MOFs) based MIM cavities, which are treated by plasma etching to provide channels for chemical diffusion and to advance sensing. We modulate the bandwidth of the MIM filters by controlling the MOF thickness as insulator layers. Oxygen plasma-etching is applied to build channels on the top metal layer without altering their saturation and brightness for chemical sensing performance. The etching time regulates the number and size of channels on the top metal layer. Sensing behavior is demonstrated on the plasma-etched MOFs-based MIM cavity when external chemicals diffuse in the cavity. In addition, we generate patterned structure of the MOFs-based MIM cavity via plasma-mask method, which can transfer to different substrates and produce a controllable structure color change for chemical sensing. Our MIM cavity may promote the advancement and applications of structural color in security imaging, color display, information anticounterfeiting, and color printing.