The invisible hand of pre-adsorbates: Unveiling oxygen's role in sculpting Cu–TiN interfaces

Copper (Cu) binding to titanium nitride (TiN) surfaces is important for applications in catalysis, sensing, and electronics. However, achieving controlled and stable Cu attachment remains challenging. In this study, Density Functional Theory with Hubbard U corrections (DFT + U) is employed to investigate how pre-adsorbed oxygen (O) and sulfur (S) influence Cu attachment and the resulting interfacial properties. Contrary to initial expectations, our calculations reveal that the presence of pre-adsorbed O and S significantly weakens the Cu–TiN interface. Direct adsorption of Cu on the TiN surface, without pre-adsorbed species, results in a much higher adsorption energy (−13.94 eV), demonstrating stronger interfacial stability compared to systems with O (−2.06 eV) or S (−1.84 eV) pre-adsorption. Although pre-adsorbed O and S can modify the interface's electronic structure, the introduction of these species ultimately weakens the Cu–TiN interaction rather than enhancing it, as initially hypothesized. Analysis of the density of states (DOS) and charge transfer shows that direct Cu–TiN bonding maintains a more robust interaction, making it more suitable for applications requiring strong metal-ceramic interfaces. These findings highlight the critical role of surface chemistry in controlling the strength of Cu–TiN interfaces. The use of DFT + U calculations provides valuable insights into the bonding mechanisms and electronic changes at these interfaces, informing future design strategies for Cu–TiN systems with tailored properties for advanced technological applications.