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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Organic Electronics and Photovoltaics III

CPP 29.1: Vortrag

Mittwoch, 19. März 2025, 15:00–15:15, H38

Energy band structure of image potential states of organic semiconductor on graphite studied by angle-resolved low-energy inverse photoelectron spectroscopy — •Tomoko Onishi¹ and Hiroyuki Yoshida^1,2 — ¹Chiba university, Chiba, Japan. — ²Chiba university MCRC, Chiba, Japan.

The image potential state of the organic semiconductor molecule on the conductive surface is of particular interest because the image potential states can be sensitive probes of interfacial electronic states. Their energy band structure (the energy-momentum relation) provides detailed information about the electron behavior. Recently, we have developed the angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS) [1,2]. This technique allows direct observation of the unoccupied states without sample damage and with the resolution better than 0.3 eV. In this study, we applied AR-LEIPS to a monolayer of copper phthalocyanine (CuPc) on highly oriented pyrolytic graphite (HOPG). The observed band structure of the image potential state was parabolic, indicating that its nature is free-electron-like along the surface plane. By fitting the band structure to a quadratic function, we obtained the effective masses of the image potential states on HOPG and CuPc/HOPG to be (1.14 * 0.02) m0 and (1.33 * 0.08) m0, respectively, where m_0 is the electron mass. The effective mass becomes heavier due to the periodic potential induced by the CuPc molecule.[1] H. Sato, H. Ishii, H. Yoshida, et al., Nature Mat. 21, 916 (2022) [2] Y. Kashimoto, H. Yoshida et al, Rev. Sci. Instrum., 94, 063903 (2023).

Keywords: organic semiconductor; low-energy inverse photoelectron spectroscopy; energy band structure; effective mass; image potential state