Atomically thin amorphous carbon with an ultralow dielectric constant

Two-dimensional (2D) materials could replace conventional electronic components. Key advances have already been made in applying 2D materials to integrated circuits, but a robust, atomically thin ultralow-k dielectric remains crucial for further circuit scaling. Minimizing parasitic capacitances, in particular, will be needed as conductor spacing shrinks below 10 nm. However, conventional amorphous or porous low-k dielectrics become unstable at nanometre thicknesses. Here we show that atomically thin amorphous carbon films can function as mechanically robust ultralow-k dielectrics with a dielectric constant of 1.35 and a dielectric strength of 28–31 MV cm−1. The films are also an effective barrier to metal-ion diffusion, with a time to failure of 1010 s at 0.8-nm thickness. Our approach relies on a low-temperature, direct and conformal growth process, which makes it promising for practical implementation in complementary metal–oxide–semiconductor technology. An amorphous carbon film with a dielectric constant of 1.35 can act as a robust ion-diffusion barrier, even at a thickness of 0.8 nm.