Yanagisawa Susumu, Morikawa Yoshitada
The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan.
J Phys Condens Matter. 2009 Feb 11;21(6):064247. doi: 10.1088/0953-8984/21/6/064247. Epub 2009 Jan 20.
We have studied the atomic geometries and the electronic properties of the tris-(8-hydroxyquinoline) aluminum (Alq(3))/Mg interface by using density functional theoretical calculations. We have found that the chemical bond is formed between the O atoms of Alq(3) and the substrate Mg atoms, and the stability of the interface structures depends on the number of O-Mg bonds. In the up configurations, where two or three O-Mg chemical bonds are formed and the Alq(3) molecular dipoles are oriented up to the vacuum side, the work function is decreased by as much as 1.1 eV or more. The interface dipole is dominated by the orientation of the molecular dipoles of Alq(3). The interface gap state reported from experiments is ascribed to the highest occupied molecular orbital (HOMO) levels of the down configurations, which may coexist with the dominant up configurations.
我们通过密度泛函理论计算研究了三（8-羟基喹啉）铝（Alq₃）/Mg界面的原子几何结构和电子性质。我们发现Alq₃的O原子与衬底Mg原子之间形成了化学键，并且界面结构的稳定性取决于O-Mg键的数量。在向上构型中，形成了两个或三个O-Mg化学键，且Alq₃分子偶极子向上指向真空侧，功函数降低多达1.1电子伏特或更多。界面偶极子由Alq₃分子偶极子的取向主导。实验报道的界面间隙态归因于向下构型的最高占据分子轨道（HOMO）能级，其可能与占主导的向上构型共存。
