Intermolecular and interlayer interactions in copper phthalocyanine films as measured with microspot photoemission spectroscopy

Abstract

The authors have applied photoemission microspectroscopy to copper phthalocyanine films grown on a graphite surface with a lateral resolution of 0.3μm and an energy resolution of 30meV. The photoemission peak due to the highest occupied molecular orbital was found to be at binding energies of 1.13, 1.23, 1.38, and 1.5eV, depending on film thickness. From the thickness and light-polarization dependence, the peaks were assigned to originate from isolated molecules, the first layer, the second layer, and multilayer, respectively. They demonstrate the capability of photoemission microspectroscopy to resolve electronic states modified by fine differences of molecular environments.