Barrier heights of metals on OH-diamond surface determined by X-ray photoelectron spectroscopy

This study systematically investigates the interfacial electronic properties of metal contacts on hydroxyl-terminated diamond (OH-diamond) using X-ray photoelectron spectroscopy (XPS). OH-diamond surfaces were prepared via high-voltage hydroxide ion treatment in deionized water, followed by deposition of Cu, Mo, and Ru ultrathin films (3 nm) to form metal/OH-diamond contacts. The barrier heights (Φ_BH) were quantified through high-resolution XPS analysis, revealing low barrier heights of 0.44 ± 0.12 eV (Cu/OH-diamond), 0.20 ± 0.12 eV (Mo/OH-diamond), and 0.48 ± 0.12 eV (Ru/OH-diamond). Comparative studies of metals on O-terminated diamond (O-diamond) and graphite interfaces were carried out. Metal/O-diamond interfaces exhibited higher barriers (0.89–1.70 eV) consistent with literature reports for Schottky contacts, while metal/graphite structures with ohmic behavior presented low barrier heights in a range from 0.33 to 0.40 eV. Notably, OH-diamond surfaces exhibited negative electron affinity (−0.67 to −0.28 eV), akin to hydrogen-terminated diamond but with improved thermal stability. These findings establish OH-diamond as a promising platform for diamond-based electronic devices, combining the advantages of low contact resistance with superior interfacial stability.