Control of the growth of ordered C60 films by chemical modification of Pt(111) surfaces

The chemisorption of C-60 on Pt(111) results in strong bonding of the adsorbed molecules to the surface and immobile adsorbates, that lead to the growth of disordered C-60 films. We show that the Pt(111) surface can be chemically modified in a controlled manner, in order to grow ordered C-60 films. Modification of the Pt(111) surface was accomplished by pre-adsorbing oxygen adatoms, hydrogen adatoms, a graphite adlayer and an ordered C-60 adlayer. Growth of C-60 films on these modified surfaces was studied by Auger electron spectroscopy (AES), low energy electron diffraction (LEED), high resolution electron energy loss spectroscopy (HREELS) and UV photoelectron spectroscopy (UPS). Chemical modification of the surface inhibited charge transfer to the C60 molecule in all cases, leading to weaker bonding and greater adsorbate mobility on the surface that contributed to the growth of ordered C-60 films. The ordering of the film can be expressed quantitatively as the intensity ratio of the dipole active T-1u(1) mode to the non-dipole active H-g(4) mode as determined by vibrational spectroscopy using HREELS. C-60 films grown on the graphite adlayer on Pt(111) were highly ordered because of the weak physisorption interactions between the adsorbate and surface. The degree of ordering upon modification of the Pt(111) surface in this study compares well to that of previous studies using different methods. (C) 1999 Elsevier Science S.A. All rights reserved.