Deposition of carbon on gold using synchrotron radiation

Abstract Carbon contamination on the surfaces of optical components in beamlines is known to cause severe loss of flux, particularly for photon energies above the C K edge (∼ 280 eV). In order to gain insight into the mechanisms by which carbon deposition occurs we have used focussed, broadband synchrotron radiation (SR) to deposit carbon on gold under controlled conditions. Carbon was deposited by photolysis of various gases at pressures in the range of 10 −8 to 10 −6 Torr. Deposition was found to be localized to the area where the SR was incident on the surface. The relative concentration of carbon was monitored using Auger electron spectroscopy. The rate of deposition was found to be proportional to pressure and inversely proportional to substrate temperature. Effects of gas composition were also studied. Of the seven gases examined, acetone and methyl methacrylate had the highest deposition rate, while ethylene had the lowest. The ramifications of these findings on carbon contamination of beamline optical components are discussed.