Tuning adhesion by chemical modifications: Diamond/Copper interfaces as a case study towards a high throughput approach

This thesis work is devoted to the study of diamond/copper interfaces and their adhesion tuning, as a representative case study in view of a high-throughput screening of diamond-like carbon (DLC) coating/metal interfaces, which are of particular interest due to their spread use in technological applications. Indeed, DLCs, exploiting the remarkable properties of diamond, are widely used in industry to reduce friction and wear in engine components, to avoid stiction in micro- and nano-electromechanical systems and to prevent corrosion of biological implants and industrial cutting tools. However, one of their main limitations concerns their spallation from the substrate. In principle, they should strongly bind to the substrate and, at the same time, exhibit a minimum adhesion to the counter surface; it is thus interesting to explore systematically how DLCs adhesion can be tuned through chemical modifications of its surfaces. We considered the interfaces constructed between Cu(111) and two relevant (111) diamond surfaces: non-reconstructed (1×1) and Pandey-reconstructed (2×1) surfaces, which represent the extreme limits of the diamond surface energy and are indicative of the fraction of sp3 and sp2 bonds in DLCs. Chemical modifications are induced through the intercalation of one atomic species between the two slabs: B, P, O, F, N, S have been chosen. For the C(111)(1×1)/Cu(111) all adatom intercalations lead to a reduction of the adhesion energy with respect to the clean case. Fluorine represents an outstanding case, reducing adhesion of 99.6%, suggesting that it could play an important role as passivating element at interfaces with diamond. The reduced reactivity of the Pandey chain reconstructed surface provides a richer scenario for the adhesion of C(111)(2×1)/Cu(111) decorated interfaces: B and N increase the adhesion of 172% and 33%, respectively; while S is the atomic species that most reduces adhesion, leading to the complete passivation of the Cu surface.