TY - JOUR
T1 - First-principles study of the dipole layer formation at metal-organic interfaces
AU - Rusu, Paul C.
AU - Giovannetti, Gianluca
AU - Weijtens, Christ
AU - Coehoorn, Reinder
AU - Brocks, Geert
PY - 2010
Y1 - 2010
N2 - We study the dipole layer formed at metal-organic interfaces by means of first-principles calculations. Interface dipoles are monitored by calculating the change in the work-function of Au, Ag, Al, Mg, and Ca surfaces upon adsorption of a monolayer of 3,4,9,10-perylene-tetra-carboxylic-di-anhydride (PTCDA), perylene, or benzene molecules. Adsorption of PTCDA leads to pinning of the work function for a range of metal substrates. It gives interface dipoles that compensate for the difference in the clean metal work functions, leading to a nearly constant work function. In contrast, adsorption of benzene always results in a decrease in the work function, which is relatively constant for all metal substrates. Both effects are found in perylene, where adsorption on low-work-function metals gives work-function pinning, whereas adsorption on high-work-function metals gives work-function lowering. The work function changes upon adsorption are analyzed and interpreted in terms of two competing effects. If the molecule and substrate interact weakly, the molecule pushes electrons into the surface, which lowers the work function. If the metal work function is sufficiently low with respect to the unoccupied states of the molecule, electrons are donated into these states, which increases the binding and the work function.
AB - We study the dipole layer formed at metal-organic interfaces by means of first-principles calculations. Interface dipoles are monitored by calculating the change in the work-function of Au, Ag, Al, Mg, and Ca surfaces upon adsorption of a monolayer of 3,4,9,10-perylene-tetra-carboxylic-di-anhydride (PTCDA), perylene, or benzene molecules. Adsorption of PTCDA leads to pinning of the work function for a range of metal substrates. It gives interface dipoles that compensate for the difference in the clean metal work functions, leading to a nearly constant work function. In contrast, adsorption of benzene always results in a decrease in the work function, which is relatively constant for all metal substrates. Both effects are found in perylene, where adsorption on low-work-function metals gives work-function pinning, whereas adsorption on high-work-function metals gives work-function lowering. The work function changes upon adsorption are analyzed and interpreted in terms of two competing effects. If the molecule and substrate interact weakly, the molecule pushes electrons into the surface, which lowers the work function. If the metal work function is sufficiently low with respect to the unoccupied states of the molecule, electrons are donated into these states, which increases the binding and the work function.
KW - METIS-265330
U2 - 10.1103/PhysRevB.81.125403
DO - 10.1103/PhysRevB.81.125403
M3 - Article
SN - 1098-0121
VL - 81
JO - Physical review B: Condensed matter and materials physics
JF - Physical review B: Condensed matter and materials physics
M1 - 125403
ER -