ATOMIC-STRUCTURE OF MONOLAYER GRAPHITE FORMED ON NI(111)

The atomic structure of monolayer graphite formed on a Ni(lll) surface was investigated by means of LEED intensity analysis. We measured the I-V curves of the (1,0), (0,1) and (1,1) diffraction spots from a (1 x 1) atomic structure, and analyzed them using Van Hove's analytical p rogram based on dynamical theory. Three different atomic structures me eting the experimental requirement of the 3m symmetry were evaluated w ith Pendry's reliability factor. The final best-fit structure characte rized by the minimum Pendry's reliability factor of 0.22 is as follows : one carbon atom in a unit cell of the graphite overlayer is located at the on-top site of the topmost Ni atoms, while another carbon atom exists at the fee hollow site. The spacing between the flat overlayer and the topmost Ni layer is 2.11 +/- 0.07 Angstrom, which is much narr ower than the interlayer spacing in bulk graphite (3.35 Angstrom). (C) 1997 Elsevier Science B.V.