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Modification of the Gallium‐Doped Zinc Oxide Surface with Self‐Assembled Monolayers of Phosphonic Acids: A Joint Theoretical and Experimental Study
Author(s) -
Li Hong,
Ratcliff Erin L.,
Sigdel Ajaya K.,
Giordano Anthony J.,
Marder Seth R.,
Berry Joseph J.,
Brédas JeanLuc
Publication year - 2014
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201303670
Subject(s) - materials science , ultraviolet photoelectron spectroscopy , density functional theory , valence (chemistry) , molecular orbital , molecule , x ray photoelectron spectroscopy , doping , fermi level , work function , binding energy , atomic orbital , chemical physics , molecular physics , electronic structure , atomic physics , computational chemistry , nanotechnology , nuclear magnetic resonance , chemistry , layer (electronics) , optoelectronics , physics , organic chemistry , quantum mechanics , electron
Gallium‐doped zinc oxide (GZO) surfaces, both bare and modified with chemisorbed phosphonic acid (PA) molecules, are studied using a combination of density functional theory calculations and ultraviolet and X‐ray photoelectron spectroscopy measurements. Excellent agreement between theory and experiment is obtained, which leads to an understanding of: i) the core‐level binding energy shifts of the various oxygen atoms belonging to different surface sites and to the phosphonic acid molecules; ii) the GZO work‐function change upon surface modification, and; iii) the energy level alignments of the frontier molecular orbitals of the PA molecules with respect to the valence band edge and Fermi level of the GZO surface. Importantly, both density of states calculations and experimental measurements of the valence band features demonstrate an increase in the density of states and changes in the characteristics of the valence band edge of GZO upon deposition of the phosphonic acid molecules. The new valence band features are associated with contributions from surface oxygen atoms near a defect site on the oxide surface and from the highest occupied molecular orbitals of the phosphonic acid molecules.