Hetero-Stacking of MXenes and Metal Thin Films for Synergistic Enhancement of Electromagnetic Interference Shielding Performance

An electronic packaging of small-form-factor devices requires a paradigm shift in electromagnetic interference (EMI) shielding layers from bulky metal cages to thin and conformal metal sheets. Unfortunately, thin-film shields exhibit inferior shielding performance compared to bulky shields. To address the thickness-limited performance, pores are intentionally formed in the shielding materials to drive internal multiple reflections/absorptions (MRA), surpassing conventional thin-film shielding performance. However, pore engineering induces processing costs, poor integration capability, and non-uniform passivation issues.<br/>In this talk, I will present our material strategies for developing high-performance thin-film EMI shields without pore engineering. We have discovered that simply stacked metal/MXene/metal thin films exhibit a shielding performance of 70 dB at a 1-μm thickness, outperforming state-of-the-art shielding materials. This synergy is attributed to the formation of EM wave confinement walls by metal/MXene heterogeneous junctions, effectively driving MRA in the MXene layer. With the embedded-MXene-in-metal (EXIM) shields, we can conformably cover flexible Schottky diode arrays and portable USB 3.0 adapters, successfully protecting them from EM noises. Additionally, I will discuss details of the EXIM shields, including the MXene/metal stacking effect, as a representative case of 2D/3D heterojunction-driven novel functionalities.