STRUCTURES OF PHYSISORBED MONOLAYERS ON AN ANISOTROPIC SUBSTRATE - XE AND N-2 ON CU(110)

The structures of Xe and N-2 monolayers physisorbed on a Cu(110) surface were investigated by means of thermal helium atom scattering. Depending on coverage and surface temperature each of the adsorbed species forms a variety of high-order commensurate structures. These structures result from the competition of the interaction between the adsorbed species and the highly anisotropic corrugation of the Cu(110) substrate. Depending on surface coverage and temperature, Xe forms a sequence of (n x 2) structures which are aligned along the close-packed Cu rows, the most stable structure exhibiting a (26 x 2) unit cell. Physisorbed nitrogen molecules form a quasi-hexagonal super-structure, which is rotated with respect to the substrate.