TY - JOUR
T1 - Band bending of n-gan under ambient h2o vapor studied by X-ray photoelectron spectroscopy
AU - Imazeki, Yuki
AU - Sato, Masahiro
AU - Takeda, Takahito
AU - Kobayashi, Masaki
AU - Yamamoto, Susumu
AU - Matsuda, Iwao
AU - Yoshinobu, Jun
AU - Sugiyama, Masakazu
AU - Nakano, Yoshiaki
N1 - Funding Information:
This experiment was performed at facilities of the Synchrotron Radiation Research Organization, The University of Tokyo (Proposal No. 2018A7556). A part of this work was supported by JSPS KAKENHI Grant No. JP18H03772 and Strategic International Research Cooperative Program, Japan Science and Technology Agency (JST). This work was partially supported by the Spintronics Research Network of Japan (Spin-RNJ).
Publisher Copyright:
© 2021 American Chemical Society. All rights reserved.
PY - 2021/5/6
Y1 - 2021/5/6
N2 - To improve the performance of semiconductor photoelectrodes for water splitting, the amount of band bending in the depletion layer of a semiconductor should be accurately ascertained, since it determines the splitting efficiency of photogenerated carriers. Band bending has been determined by X-ray photoelectron spectroscopy (XPS) from the valence band maximum (VBM), which has been calculated from the Ga 3d peak using the energy difference between VBM and Ga 3d (ΔEVBM-3d). This work validates several values for ΔEVBM-3d which have been reported previously, by analyzing the spectrum around the VBM and its distance from Ga 3d for the n-GaN(0001) surface under both ultrahigh vacuum (UHV) and ambient H2O. ΔEVBM-3d is estimated to be between 17.36 and 17.55 eV. By adopting 17.5 eV as ΔEVBM-3d, the amounts of band-bending were 0.5 eV under UHV and 0.1 eV under a relative humidity of 46%, respectively. For the latter condition, a surface photovoltage of 20 meV was observed upon Xe lamp irradiation, confirming the existence of band bending even with H2O adsorption on the surface. The origin of such band bending seems to be Fermi level pinning to the subsurface states which cannot be compensated by H2O.
AB - To improve the performance of semiconductor photoelectrodes for water splitting, the amount of band bending in the depletion layer of a semiconductor should be accurately ascertained, since it determines the splitting efficiency of photogenerated carriers. Band bending has been determined by X-ray photoelectron spectroscopy (XPS) from the valence band maximum (VBM), which has been calculated from the Ga 3d peak using the energy difference between VBM and Ga 3d (ΔEVBM-3d). This work validates several values for ΔEVBM-3d which have been reported previously, by analyzing the spectrum around the VBM and its distance from Ga 3d for the n-GaN(0001) surface under both ultrahigh vacuum (UHV) and ambient H2O. ΔEVBM-3d is estimated to be between 17.36 and 17.55 eV. By adopting 17.5 eV as ΔEVBM-3d, the amounts of band-bending were 0.5 eV under UHV and 0.1 eV under a relative humidity of 46%, respectively. For the latter condition, a surface photovoltage of 20 meV was observed upon Xe lamp irradiation, confirming the existence of band bending even with H2O adsorption on the surface. The origin of such band bending seems to be Fermi level pinning to the subsurface states which cannot be compensated by H2O.
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U2 - 10.1021/acs.jpcc.0c11174
DO - 10.1021/acs.jpcc.0c11174
M3 - Article
AN - SCOPUS:85106440164
SN - 1932-7447
VL - 125
SP - 9011
EP - 9019
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 17
ER -
