Angle-resolved UV photoelectron spectra (UPS) of thin films of perylene-3,4,9,10-tetracarboxylic dianhydride on MoS₂

Angle-resolved UV photoelectron spectra (ARUPS) were measured for thin films of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) deposited on cleaved MoS₂ surfaces. The take-off angle (θ) dependence of the photoelectron intensity of the highest π band showed a sharp maximum at θ = 32–34°. A spectral feature of the binding energy at ∼8.9 eV, which is believed to originate from a π state, showed a remarkably different θ dependence from that of the π band. A quantitative analysis of the observed θ dependencies clearly indicates that (a) the feature at ∼8.9 eV originates from the oxygen 2p non-bonding states and (b) the molecules lie flat on the substrate surface.