Ab-initio study of Schottky barrier heights at metal-diamond (1 1 1) interfaces

Diamond electronic devices have attracted great attention in the field of high power and high frequency applications due to their excellent properties. For diamond electronics, metal and diamond contacts are important for the electronic device performance, with Schottky barrier heights (SBHs) playing a crucial role in the transmission properties of diamond devices. To make sense of their electrical characteristics, the interface supercells of diamond (1 1 1) with diverse metals have been explored using first-principles calculations. Clear metal-induced gap states (MIGS) can be observed at the interface, resulting in an enhanced Fermi-level pinning effect, with a pinning factor of 0.3. The results surprisingly show that there is a larger transverse tunneling probability and a smaller longitudinal tunneling probability for all diamond contact interfaces. All interfaces studied are p-type contacts with the metal Fermi level close to the diamond valance band edge. The low work function metals such as Sc and Ti are excellent at generating Schottky contacts with relatively higher SBHs (∼1.0 eV ± 0.6 eV). Pt and Ni have a smallest barrier height of ∼ 0.5 eV, making them ideal for ohmic electrodes with low contact resistance. The calculated SBHs are within the range of the experimental findings. This work gives insight into the electrical structural changes at the contact interface between metal and diamond, which provides a theoretical basis for selecting suitable electrodes for high-power diamond devices.