RESUMEN
Copper (Cu) is widely used as an industrial electrode due to its high electrical conductivity, mechanical properties, and cost-effectiveness. However, Cu is susceptible to corrosion, which degrades device performance over time. Although various methods (alloying, physical passivation, surface treatment, etc.) are introduced to address the corrosion issue, they can cause decreased conductivity or vertical insulation. Here, using the nitrogen-doped amorphous carbon (a-C:N) thin film is proposed as a substrate on which Cu is directly deposited. This simple method significantly inhibits corrosion of ultrathin Cu (<20 nm) films in humid conditions, enabling the fabrication of ultrathin electronic circuit boards without corrosion under ambient conditions. This study investigates the origin of corrosion resistance through comprehensive microscopic/spectroscopic characterizations and density-functional theory (DFT) calculations: i) diffusion of Cu atoms into the a-C:N driven by stable C-Cu-N bond formation, ii) diffusion of N atoms from the a-C:N to the Cu layer heading the top surface, which is the thermodynamically preferred location for N, and iii) the doped N atoms in Cu layer suppress the inclusion of O into the Cu lattice. By leveraging the ultrathinness and deformability of the circuit board, a transparent electrode and a crumpleable LED lighting device are demonstrated.
RESUMEN
While various crystalline carbon allotropes, including graphene, have been actively investigated, amorphous carbon (a-C) thin films have received relatively little attention. The a-C is a disordered form of carbon bonding with a broad range of the CC bond length and bond angle. Although accurate structural analysis and theoretical approaches are still insufficient, reproducible structure-property relationships have been accumulated. As the a-C thin film is now adapted as a hardmask in the semiconductor industry and new properties are reported continuously, expectations are growing that it can be practically used as active materials beyond as a simple sacrificial layer. In this perspective review article, after a brief introduction to the synthesis and properties of the a-C thin films, their potential practical applications are proposed, including hardmasks, extreme ultraviolet (EUV) pellicles, diffusion barriers, deformable electrodes and interconnects, sensors, active layers, electrodes for energy, micro-supercapacitors, batteries, nanogenerators, electromagnetic interference (EMI) shielding, and nanomembranes. The article ends with a discussion on the technological challenges in a-C thin films.