Local electronic structure at organic-metal interface studied by UPS, MAES, and first-principles calculation

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• 作者：M. Aoki ; ^{cmaoki@mail.ecc.u-tokyo.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; S. Masuda
• 关键词：Organic&ndash ; metal interface ; Valence electronic state ; Ultraviolet photoemission spectroscopy ; Metastable atom electron spectroscopy ; First-principles calculation
• 刊名：Journal of Electron Spectroscopy and Related Phenomena
• 出版年：2015
• 出版时间：1 October 2015
• 年：2015
• 卷：204
• 期：part_PA
• 页码：68-74
• 全文大小：2071 K

文摘

Understanding and controlling local electronic structures at organic–metal interfaces are crucial for fabricating novel organic-based electronics, as in the case of heterojunctions in semiconductor devices. Here, we report recent studies of valence electronic states at organic–metal interfaces (especially those near the Fermi level of a metal substrate) by the combined analysis of ultraviolet photoemission spectroscopy (UPS), metastable atom electron spectroscopy (MAES), and first-principles calculations. New electronic states in the HOMO (highest occupied molecular orbital)–LUMO (lowest unoccupied molecular orbital) gap formed at an organic–metal interface are classified as a chemisorption-induced gap state (CIGS) and a complex-based gap state (CBGS). The CIGS is further characterized by an asymptotic feature of the metal wave function in the chemisorbed species. The CIGSs in alkanethiolates on Pt(1 1 1) and C₆₀ on Pt(1 1 1) can be regarded as damping and propagating types, respectively. The CBGSs in K-doped dibenzopentacene (DBP) are composed of DBP-derived MOs and K sp states and distributed over the complex film. No metallic structures were found in the K₁DBP and K₃DBP phases, suggesting that they are Mott–Hubbard insulators due to strong electron correlation. The local electronic structures of a pentacene film bridged by Au electrodes under bias voltages were examined by an FET-like specimen. The pentacene-derived bands were steeply shifted at the positively biased electrode, reflecting the p-type character of the film.