Interfacial reaction of erbium on homoepitaxial diamond (100) films

The atomic and electronic characteristics of homoepitaxial C(100) thin films and their reactions with very thin erbium deposits have been studied by low-energy electron diffraction (LEED) and photoelectron spectroscopy (X-ray photoelectron spectroscopy [XPS] and ultraviolet photoelectron spectroscopy [UPS]). These films, of 3 μm thick, are grown by microwave chemical vapor deposition (CVD) and p-doped (1017 B/cm3). Measurements are made on two types of surfaces: plasma-hydrogenated and chemically oxidized. The hydrogenated surfaces exhibit 2(2×1) LEED pattern and negative electron affinity (NEA). Under annealing at high temperature (500–650°C) in oxygen (1 to 5×10−5 mbar), the hydrogenated surface is transformed slowly into an oxidized one which has the same atomic and electronic structures as the chemically oxidized surface, namely a (1×1) LEED diagram and a positive electron affinity (PEA). Under annealing at high temperature, erbium deposits react with the hydrogenated surface and not with the oxidized one. The reaction is not complete and produces a very thin interface erbium carbide layer. Internal photoemission measurements performed on erbium carbide/diamond contacts, protected against oxidation by a layer of erbium silicide, show potential barrier heights close to 1.9 eV.