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) deposi ted on cleaved MoS2 surfaces. The take-off angle (theta) dependence of the photoelectron intensity of the highest pi band showed a sharp max imum at theta = 32-34 degrees. A spectral feature of the binding energ y at similar to 8.9 eV, which is believed to originate from a pi state , showed a remarkably different a dependence from that of the pi band. A quantitative analysis of the observed a dependencies clearly indica tes that (a) the feature at similar to 8.9 eV originates from the oxyg en 2p non-bonding states and (b) the molecules lie flat on the substra te surface.