Depto. Superficies y Recubrimientos, Instituto de Ciencia de Materiales de Madrid (CSIC), ES-28049 Madrid, Spain.
J Chem Phys. 2013 Dec 7;139(21):214706. doi: 10.1063/1.4836635.
The interface between the tetrathiafulvalene/tetracyanoquinodimethane (TTF-TCNQ) organic blend and the Au(111) metal surface is analyzed by Density Functional Theory calculations, including the effect of the charging energies on the molecule transport gaps. Given the strong donor and acceptor characters of the TTF and TCNQ molecules, respectively, there is a strong intermolecular interaction, with a relatively high charge transfer between the two organic materials, and between the organic layer and the metal surface. We find that the TCNQ LUMO peak is very close to the Fermi level; due to the interaction with the metal surface, the organic molecular levels are broadened, creating an important induced density of interface states (IDIS). We show that the interface energy level alignment is controlled by the charge transfer between TTF, TCNQ, and Au, and by the molecular dipoles created in the molecules because of their deformations when adsorbed on Au(111). A generalization of the Unified-IDIS model, to explain how the interface energy levels alignment is achieved for the case of this blended donor/acceptor organic layer, is presented by introducing matrix equations associated with the Charge Neutrality Levels of both organic materials and with their intermixed screening properties.
通过密度泛函理论计算，分析了四硫富瓦烯/四氰基对醌二甲烷（TTF-TCNQ）有机混合物与 Au(111)金属表面之间的相互作用，包括充电能对分子输运间隙的影响。鉴于 TTF 和 TCNQ 分子分别具有很强的给体和受体性质，因此它们之间存在很强的分子间相互作用，两种有机材料之间以及有机层与金属表面之间存在较高的电荷转移。我们发现 TCNQ 的 LUMO 峰非常接近费米能级；由于与金属表面的相互作用，有机分子能级变宽，形成了重要的界面态密度（IDIS）。我们表明，界面能级排列由 TTF、TCNQ 和 Au 之间的电荷转移以及分子在吸附到 Au(111)时因变形而产生的分子偶极子控制。通过引入与两种有机材料的电荷中性水平及其混合屏蔽特性相关的矩阵方程，提出了统一 IDIS 模型的推广，以解释这种混合施主/受主有机层中如何实现界面能级排列。
