Interfacial properties at the organic-metal interface probed using quantum well states

Using angle-resolved photoemission spectroscopy, we investigated the interfacial properties between the long-chain normal-alkane molecule n-CH ₃(CH ₂) ₄₂CH ₃ [tetratetracontane (TTC)] and uniform Ag films using the Ag quantum well states. The entire quantum well state energy band dispersions were observed to shift toward the Fermi level with increasing adsorption coverage of TTC up to 1 monolayer (ML). However, the energy shifts upon deposition of 1 ML of TTC are approximately inversely dependent on the Ag film thickness, indicating a quantum-size effect. In the framework of the pushback and image-force models, we applied the Bohr-Sommerfeld quantization rule with the modified Coulomb image potential for the phase shift at the TTC/Ag interface to extract the dielectric constant for 1 ML of TTC.