Adsorption study of thin films of terephthalic acid and substituted benzoic acids on HOPG studied by Metastable Induced Electron Spectroscopy and Ultraviolet Photoelectron Spectroscopy

Highlights: • Adsorption Study of 4-alkoxybenzoic acids and terephthalic acid (TPA) on HOPG with MIES. • Flat adsorption of the molecules in the monolayer range. • For 4-decoxy benzoic acid, a reorientation of the long alkyl chains in transition to the multilayer. - Abstract: The adsorption behavior of thin films of 4-alkoxybenzoic acids (with either hydroxy-, methoxy-, propoxy-, pentoxy- and decoxy-chains) and terephthalic acid, evaporated on a Highly Oriented Pyrolytic Graphite (HOPG) surface was studied. The orientation of the molecules was characterized by Metastable Induced Electron Spectroscopy (MIES) and Ultraviolet Photoelectron Spectroscopy (UPS(HeI)). On HOPG the 4-alkoxybenzoic acids and the terephthalic acid show a layer like growth at the beginning. Since the MIE spectra for the molecules on HOPG show all molecular orbitals, especially the π orbitals of the phenyl ring, a flat laying orientation on the graphite surface is assumed. The only exception is observed for 4-decoxy-benzoic acid. After a coverage of approximately 1 monolayer (ML) the spectrum is dominated by the spectral features of the alkyl structures.