The structure and mobility of carbon on Ru(001)

Abstract

Interaction of ethylene with Ru(001) at temperatures above 300 K causes carbon to be deposited on the surface. Thermal desorption spectroscopy (TDS) of CO adsorbed on the precarburized surface shows that at carbon coverages below 0.5 ML the CO bond to the surface is weakened, but the adsorption capacity is only slightly diminished. At carbon coverages above 0.5 ML, CO adsorption sites are blocked. Temperature programmed oxidation (TPO) of the carbon layer shows a first-order peak at 570 K which indicates carbon-oxygen neighbors and a peak at ≈ 650K that requires mobility in the surface layer. CO TDS, TPO, Auger electron spectroscopy (AES), and SIMS all show that annealing the carbon layer causes growth of graphitic islands that starts at ≈ 600 K and is complete at ≈ 900 K. Temperatures above 1145 K cause dissolution of carbon into the bulk. The island formation, which requires a minimum carbon coverage, is indicated by increased CO uptake, a high-temperature TPO peak, loss of the AES carbidic feature, and restricted isotope mixing in the C 2 − ions in SIMS of 13C deposited on an annealed 12C surface. The SIMS experiments demonstrate the use of this technique for the study of proximity and structure in surface layers.