title: Two charged states of hydrogen on the SrTiO3(001) surface.
abstract: The effects of hydrogen exposure on the electronic structure of two types of SrTiO3(001) surfaces, oxygen-deficient (OD) and nearly-vacancy-free (NVF) surfaces, were investigated with ultraviolet photoemission spectroscopy and nuclear reaction analysis. Upon molecular hydrogen exposure to the OD surface which reveals in-gap states at 1.3 eV below the Fermi level, the in-gap state intensity was reduced to half the initial value at a hydrogen coverage of 0.9 ± 0.7 × 10(14) cm(-2). On the NVF surface which has no in-gap state, on the other hand, atomic-hydrogen exposure induced in-gap states, and the hydrogen saturation coverage was evaluated to be 3.1 ± 0.8 × 10(14) cm(-2). We argue that H is positively charged as H(∼0.3 +) on the NVF surface by being coordinated to the O atom, whereas H is negatively charged as H(-) on the OD surface by occupying the oxygen vacancy site. The stability of H(-) at the oxygen vacancy site is discussed.
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Takeyasu
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Fukada
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Shohei
authors.initials: S
authors.lastname: Ogura
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Masuaki
authors.initials: M
authors.lastname: Matsumoto
authors.affiliation: Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Fukutani