Adsorption Structure and Work Function of Succinic Acid on Cu(110) Surface

Abstract

The relation between the adsorption structure and the work function of succinic acid (HOOC-CH2-CH2-COOH) on Cu(110) surface, has been investigated as a function of the surface temperature using reflection absorption infrared spectroscopy, low energy electron diffraction, He atom scattering, temperature programmed desorption and Kelvin probe. From 350 to 450 K, succinic acid adsorbed as monosuccinate (HOOC-CH2-CH2-COO^-) form. As the temperature increases, each monosuccinate make a dimer structure. From 450 K, monosuccinate changes to bisuccinate (^-OOC-CH2-CH2-COO^-) form. Bisuccinate structure is stable until 600 K and then desorption and dissociation occurred. The work function increased by adsorption due to ionization of molecules, and decreased with increasing the temperature until 450 K due to the effects of change in the dipole moment of the conformational change of the molecule. From 450 K to 600 K the work function was constant, because of competition between desorption and change in the dipole moment of molecules, and then it reached the value of clean surface. It was experimentally clarified that the work function was affected by the difference in the state of conformation of molecules adsorbed.