Investigation of 1D chain formation of CO on Pd(110) by low temperature scanning tunneling microscope

In order to investigate intermolecular interaction between adsorbed molecul es, we directly observed adsorbed structures of low coverage CO on Pd(1 1 0 ) using a low-temperature (4.7 K) scanning tunneling microscope. We found t hat the CO molecules dosed at room temperature prefer to form a one-dimensi onal (1D) chain along [1 (1) over bar 0] during the cooling down, in contra st to a random distribution of CO dosed at near liquid He temperature. Thes e results show the existence of an attractive force between CO molecules ch emisorbed on Pd(1 1 0) along [1 (1) over bar 0]. Here, we discuss effective intermolecular interactions for the ID chain formation with energy estimat ions of individual interaction elements between chemisorbed CO molecules. ( C) 2001 Elsevier Science B.V. All rights reserved.