The electronic passivation of small-form-factor devices requires a fundamental change in electromagnetic interference (EMI) shielding, transitioning from bulky metal cans to conformal thin films1–4. However, reducing the thickness induces poor shielding performance associated with the skin depth of shielding materials5,6. To overcome the performance limitations of thin-film shields, absorption during multiple internal reflections should be driven7. For absorption during multiple internal reflections, pores have been intentionally introduced into shielding materials such as metals8–12 and two-dimensional (2D) titanium carbides/nitrides (MXenes)13–19. However, these approaches involve insufficient thinness, non-uniformity and/or processing incompatibility. Here we propose embedding non-porous MXene film into metal thin films to achieve unprecedented shielding performance at a thickness of just 1 μm (about 70 decibels; about 80 decibels at 1.9-μm thickness) without the limitations associated with porous structures. This exceptional performance in simple-stacked metal/MXene/metal structures, which deviates from the typical thickness dependency, arises from the formation of electromagnetic wave confinement walls at the interfaces, driven by the conductivity mismatch between the metal and MXene. The confined electromagnetic waves within the MXene ‘well’ are effectively attenuated through polarization loss, primarily driven by dipoles at the metal–MXene interfaces. Our embedded-MXene-in-metal shields provide conformal EMI protection for portable USB (Universal Serial Bus) 3.0 flash drives and flexible Schottky diodes. Our embedded-MXene-in-metal shields may open new avenues in packaging technologies, enabling EMI-free ubiquitous electronics.
