AN STM STUDY OF THE INTERACTION OF BENZENE WITH AN OXYGEN-PRECOVERED NI(110) SURFACE

The interaction of benzene (C6H6) with a Ni(110) surface with preadsorbed oxygen has been investigated in ultra-high vacuum at room temperature (RT) using scanning tunneling microscopy (STM). At an initial O coverage of similar to 0.30 monolayers, the benzene induces a compression of the -Ni-O- added rows from a (3 X 1) to a (2 X 1) structure, and the C6H6 molecules decorate the troughs which have been created by the compression. Annealing to similar to 400 K induces H scission which is accompanied by the disappearance of C6H6 molecules in the STM images. By further heating, the surface is observed to undergo a complicated structural transformation in which the oxygen is finally removed by recombinative CO desorption, and after heating to similar to 600 K, the surface is clean, apart from areas which are covered by the carbidic p(4 X 5)C phase. No signs of a direct reaction between C6H6 and O have been observed at RT, even at a lower initial O coverages.