Controllable Structurally Randomized Cu Mesh Films for EMI-Shielded Optical Windows with Slight Imaging Quality Degradation
This work presents a cracked template and vacuum metal evaporation strategy for fabricating structurally randomized copper (Cu) mesh films. Regulating the internal stress distribution within the coating during template cracking enables controlled fabrication of Cu mesh films with varying discrete degrees of mesh aperture area and distinct probability distributions of metal line inclination. The influence of structural parameter randomization on properties was systematically investigated, encompassing higher-order diffraction energy homogenization, optoelectronic performance, and electromagnetic interference shielding effectiveness (EMI SE). Results demonstrate that increasing structural randomization effectively suppresses higher-order diffraction energy, achieving a reduction to −3.93 dB in normalized higher-order diffraction energy. Furthermore, the Cu mesh film exhibited minimal degradation on imaging system performance, with resolution decreasing only marginally from 80.6 to 71.8 lp/mm. Simultaneously, the most randomized Cu mesh film demonstrates an ultra-low sheet resistance (3.31 Ω/sq), high visible light transmittance (88.7% at 550 nm), an exceptional figure of merit (FoM=913.69), and robust EMI SE within the X-band (average SE of 33.18 dB). These findings underscore that metal mesh films incorporating structural randomization offer an effective strategy for enhancing EMI shielding in high-performance optoelectronic imaging systems.