| AVS 61st International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | Hirofumi Sato, The University of Tokyo, Japan |
| Authors: | H. Sato, The University of Tokyo, Japan S. Mihara, The University of Tokyo, Japan M. Aoki, The University of Tokyo, Japan K. Shudo, Yokohama National University, Japan K. Akimoto, University of Tsukuba, Japan S. Masuda, The University of Tokyo, Japan |
| Correspondent: | Click to Email |
Electronic properties of potassium-doped dibenzopentacene (DBP) thin films on Au(111) were studied by ultraviolet photoemission spectroscopy (UPS), metastable atom electron spectroscopy (MAES),1,2 and first-principles DFT calculation. The UPS and MAES spectra for KxDBP (0 ≤ x ≤ 3.5) films show three types of gap state (GS1~GS3) in the HOMO–LUMO gap of pristine DBP. The GS1 and GS2 emerge at the initial stage of deposition and are attributed to the modified HOMO state and partially-filled LUMO state, respectively. The threshold of electron emission for K1DBP is located ~0.1 eV below the Fermi level (EF) with no metallic feature, suggesting that K1DBP is a Mott-Hubbard insulator. At the formation of K2DBP, the GS1 and GS2 saturate in intensity and shift to the higher binding energy. This indicates that the native LUMO state is fully occupied by electron transfer, resulting in a wide-gap insulator. Upon further deposition, the GS3 appears near EF and is attributed to partial electron filling in the LUMO+1~LUMO+3 states. For K3.5DBP, the leading edge of GS3 is located ~0.1 eV below EF without a metallic feature. Therefore, the heavily doped species transfers to a Mott-Hubbard insulator again. The GS3 plays a key role in superconductivity of K3DBP at low temperature.3
The interaction of alkaline-metal atoms with aromatic hydrocarbons could be classified into three categories, i.e., weak interaction,4 simple charge transfer,5 and heavy mixing of mutual wave functions. The K-doped DBP belongs to third category, and the detail will be discussed in the conference.
References
[1] Y. Harada, S. Masuda, H. Ozaki, Chem. Rev. 97, 1897 (1997).
[2] S. Masuda, Appl. Surf. Sci. 256, 4054 (2010).
[3] M. Xue, T. Cao, D. Wang, Y. Wu, H. Yan X. Dong, J. He, F. Li, G. F. Chen, Sci. Rep.2, 1 (2012).
[4] M. Sogo, Y. Sakamoto, M. Aoki, S. Masuda, J. Chem. Phys. 133, 134704 (2010).
[5] F. Bussolotti, S. Kera, N. Ueno, Phys. Rev. B 86, 155120 (2012).