In this paper, we obtain the energy band positions of amorphous carbon (a–C) surfaces in vacuum and in aqueous environment. The calculations are performed using a combination of (i) classical molecular dynamics (MD), (ii) Kohn-Sham density functional theory with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, and (iii) the screened-exchange hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE). PBE allows an accurate generation of a-C and the evaluation of the local electrostatic potential in the a-C/water system, HSE yields an improved description of energetic positions which is critical in this case, and classical MD enables a computationally affordable description of water. Our explicit calculation shows that, both in vacuo and in aqueous environment, the a-C electronic states available in the region comprised between the H2/H2O and O2/H2O levels of water correspond to both occupied and unoccupied states within the a-C pseudogap region. These are localized states associated to sp2 sites in a-C. The band realignment induces a shift of approximately 300 meV of the a-C energy band positions with respect to the redox levels of water.
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21 January 2015
Research Article|
January 15 2015
Energy band alignment and electronic states of amorphous carbon surfaces in vacuo and in aqueous environment
Miguel A. Caro
;
Miguel A. Caro
a)
1Department of Electrical Engineering and Automation,
Aalto University
, Espoo, Finland
2Department of Applied Physics, COMP Centre of Excellence in Computational Nanoscience,
Aalto University
, Espoo, Finland
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Jukka Määttä;
Jukka Määttä
3Department of Chemistry,
Aalto University
, Espoo, Finland
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Olga Lopez-Acevedo
;
Olga Lopez-Acevedo
2Department of Applied Physics, COMP Centre of Excellence in Computational Nanoscience,
Aalto University
, Espoo, Finland
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Tomi Laurila
Tomi Laurila
1Department of Electrical Engineering and Automation,
Aalto University
, Espoo, Finland
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a)
Electronic mail: mcaroba@gmail.com
J. Appl. Phys. 117, 034502 (2015)
Article history
Received:
October 17 2014
Accepted:
January 01 2015
Citation
Miguel A. Caro, Jukka Määttä, Olga Lopez-Acevedo, Tomi Laurila; Energy band alignment and electronic states of amorphous carbon surfaces in vacuo and in aqueous environment. J. Appl. Phys. 21 January 2015; 117 (3): 034502. https://doi.org/10.1063/1.4905915
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