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1999
Conference Paper
Titel
Electronic properties of CVD diamond surfaces. Modification through adsorption of carbon
Alternative
Elektronische Eigenschaften von CVD-Diamantoberflächen. Modifikation durch Adsorption von Kohlenstoff
Abstract
In this study the interaction of the diamond surface with carbon has been examined. Carbon, which is supplied by electron beam evaporation of graphite, is deposited on polycrystalline diamond films of random and (100) orientation. Carbon films with a thickness between 0.2 and 40 monolayers (ML) are deposited on the diamond surface at two different substrate temperatures (ambient and 700 deg C). The interface formation and subsequent carbon film growth is monitored by photoelectron spectroscopy in the ultraviolet (UPS) and X-ray (XPS) regime, which probes the electronic structure of the surface. The UPS spectra clearly show that diamond growth cannot be continued in this hydrogen-free environment, and amorphous carbon films are formed. We found that the overlayer structure is not decisively influenced by the interaction with the diamond surface: ultrathin films possess already the characteristic film structure for the respective deposition temperature. The analysis of the Cls core level spectra shows, that the carbon growth occurs most likely through a layer-by-layer growth or the formation of flat islands. The diamond component of the Cls peak is shifted markedly to higher binding energies in the course of the deposition, the magnitude of the shift is between 0.2 and 0.9 eV, depending on the diamond substrate. The origin of the downward band bending leading to the observed shift, lies in the loss of surface hydrogen and/or the alignment of the substrate and overlayer Fermi levels (Schottky barrier formation).