UPS study of electronic states of CuPc/Ag(110)

Abstract

The electronic structure of copper phthalocyanine (CuPc) adsorbed on Ag (110) surface has been investigated by using the ultra-violet photoemission spectra (UPS). The signals from the 3d band of the substrate Ag atoms faded, while two new peaks grew at 4.45 and 6.36eV below the Fermi level with increasing coverage of CuPc molecules. With further increasing the CuPc coverage, other two peaks can be detected at 1.51 and 9.20 eV below the Fermi level. All four peaks originate from CuPc molecules. With increasing CuPc coverage, the four peaks increase in intensity and shift in binding energy. The results of angular resolved UPS suggest a “flat-lying" mode for CuPc molecules adsorbed on Ag (110) surface. And this has been supported by the theoretical calculation based on the density functional theory (DFT). The theoretical study shows that the CuPc molecule prefers to lie on the hollow position of Ag substrate.