title: Role of Quantum and Surface-State Effects in the Bulk Fermi-Level Position of Ultrathin Bi Films.
abstract: We performed high-resolution photon-energy and polarization-dependent ARPES measurements on ultrathin Bi(111) films [6-180 bilayers (BL), 2.5-70 nm thick] formed on Si(111). In addition to the extensively studied surface states (SSs), the edge of the bulk valence band was clearly measured by using S-polarized light. We found direct evidence that this valence band edge, which forms a hole pocket in the bulk Bi crystal, does not cross the Fermi level for the 180 BL thick film. This is consistent with the predicted semimetal-to-semiconductor transition due to the quantum-size effect [V.B. Sandomirskii, Sov. Phys. JETP 25, 101 (1967)]. However, it became metallic again when the film thickness was decreased (below 30 BL). A plausible explanation for this phenomenon is the modification of the charge neutrality condition due to the size effect of the SSs.
authors.affiliation: Department of Physics, Tokyo Institute of Technology, Tokyo 152-8551, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hirahara
authors.affiliation: Department of Physics, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shirai
authors.affiliation: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hajiri
authors.affiliation: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Matsunami
authors.affiliation: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.affiliation: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kimura
authors.affiliation: Department of Physics, University of Tokyo, Tokyo 113-0033, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Hasegawa
authors.affiliation: Department of Physics, Ochanomizu University, Tokyo 112-8610, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi