Energy-level alignment of a single molecule on ultrathin insulating film

Miyabi Imai-Imada, Hiroshi Imada, Kuniyuki Miwa, Jaehoon Jung, Tomoko K. Shimizu, Maki Kawai, Yousoo Kim

研究成果: Article査読

7 被引用数 (Scopus)


Elucidation of the energy-level alignment mechanism at a molecule/insulator/metal interface is a key to understanding the molecular and interfacial phenomena. Herein, we provide a detailed investigation into the electronic structures of a free-base phthalocyanine on NaCl films of various thicknesses using scanning tunneling microscopy/spectroscopy (STM/STS). The energy of the ionization and the affinity levels of the molecule were deduced from the STS spectra, and we determined their dependence on the NaCl-film thickness, which can be explained based on three effects: a voltage drop within the NaCl films, the degree of electric-field screening around the molecule, and a variation in the work function of the substrates. We further found that the energy levels relative to the vacuum level are independent of the work function of the substrate, and that the size of the energy gap increases with the thickness. Our results suggest that it is possible to predict the energy levels at the interfaces based on the energy levels of the molecules in a gas phase, the work function of the substrate, and the thickness of the insulating films.

ジャーナルPhysical Review B
出版ステータスPublished - 2018 11 15

ASJC Scopus subject areas

  • 電子材料、光学材料、および磁性材料
  • 凝縮系物理学


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