Interactions of low energy reactive ions with surfaces. IV. Chemically bonded diamond-like films from ion-beam deposition

Abstract

Low energy (10–300 eV) mass-selected C+ ion beams are used to deposit thin carbon films on surfaces of Si(100), Ni(111), Ta, W, and Au in a UHV environment at room temperature. The films are characterized by Auger electron spectroscopy (AES), x-ray and UV photoelectron spectroscopy (XPS and UPS), valence level electron energy loss spectroscopy (ELS), K-shell ionization loss spectroscopy (ILS), and ellipsometry. The initial monolayer of the deposited film is in the form of a carbide layer which is chemically bonded to the substrate atoms. The film evolves gradually over the next several layers deposited, through intermediate structures, into a diamond-like structure. The diamond-like structure is confirmed by comparing the results of the above spectroscopic measurements with those of pure diamond and graphite and by referring to band structure calculations. A phase diagram, prepared as C+ ion dose vs C+ kinetic energy Ek, shows the regions of the different structures. The optimum C+ energy range for formation of the diamond-like structure is 30–175 eV. Below 10 eV the final diamond-like structure has not been attained and above 180 eV there is a sharp increase in the dose required to attain this final structure. The films are found to be free of impurities, inert to O2 chemisorption, structurally stable up to 350 °C, have a low sputtering yield, and have a sharp interface with the substrate surface. The mechanism of film deposition and growth is discussed.