Tailoring band gaps of insulators by adsorption at surface defects

Benzoic acids on NaCl surfaces

verfasst von: Wei Chen, Christoph Tegenkamp, Herbert Pfnür, Thomas Bredow
Abstract: The adsorption of benzoic acid and its OH-substituted derivatives, namely, salicylic acid (SA) and parasalicylic acid on various NaCl surfaces has been investigated by density-functional theory with hybrid exchange-correlation functional. The ideal NaCl(100) surface is chemically inert as evidenced by the low binding energies. The molecular adsorption can be enhanced by both an anion vacancy and a surface step site. The bonding between the surface Na and the carboxylic O atom is of covalent character for all adsorption geometries. Our calculations show that the adsorption of SA has the largest binding energy of all three acids due to the additional interaction between Na and the phenolic O atom. Charge transfer between the molecule and the surface is generally very small, except in the presence of an anion vacancy where the unpaired electron is mostly transferred to the adsorbate. Surface defects generally have a strong influence on the electronic structure of the adsorbed molecules. Specifically, the adsorption of SA at [011]-oriented steps can significantly reduce the effective band gap to 1.6 eV due to the up shift of the Cl3p levels at the undercoordinated step edge. Implications of these results to the contact charging effect between wide-band-gap insulators will be discussed.
Organisationseinheit(en): Institut für Festkörperphysik
Externe Organisation(en): Rheinische Friedrich-Wilhelms-Universität Bonn
Typ: Artikel
Journal: Physical Review B - Condensed Matter and Materials Physics
Band: 79
ISSN: 1098-0121
Publikationsdatum: 17.06.2009
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Elektronische, optische und magnetische Materialien, Physik der kondensierten Materie
Elektronische Version(en): https://doi.org/10.1103/PhysRevB.79.235419 (Zugang: Unbekannt)

BibTeX

@article{21ea6dc5351d49909485aeaa0dea41b9,
title = "Tailoring band gaps of insulators by adsorption at surface defects: Benzoic acids on NaCl surfaces",
abstract = "The adsorption of benzoic acid and its OH-substituted derivatives, namely, salicylic acid (SA) and parasalicylic acid on various NaCl surfaces has been investigated by density-functional theory with hybrid exchange-correlation functional. The ideal NaCl(100) surface is chemically inert as evidenced by the low binding energies. The molecular adsorption can be enhanced by both an anion vacancy and a surface step site. The bonding between the surface Na and the carboxylic O atom is of covalent character for all adsorption geometries. Our calculations show that the adsorption of SA has the largest binding energy of all three acids due to the additional interaction between Na and the phenolic O atom. Charge transfer between the molecule and the surface is generally very small, except in the presence of an anion vacancy where the unpaired electron is mostly transferred to the adsorbate. Surface defects generally have a strong influence on the electronic structure of the adsorbed molecules. Specifically, the adsorption of SA at [011]-oriented steps can significantly reduce the effective band gap to 1.6 eV due to the up shift of the Cl3p levels at the undercoordinated step edge. Implications of these results to the contact charging effect between wide-band-gap insulators will be discussed.",
author = "Wei Chen and Christoph Tegenkamp and Herbert Pfn{\"u}r and Thomas Bredow",
year = "2009",
month = jun,
day = "17",
doi = "10.1103/PhysRevB.79.235419",
language = "English",
volume = "79",
journal = "Physical Review B - Condensed Matter and Materials Physics",
issn = "1098-0121",
publisher = "American Institute of Physics",
number = "23",
}