界面电子结构该怎么理解

lyfchem

当一个氧化物负载金属，例如Au20/TiO2, 界面电子态会相应的形成，如下列文献如阐述，
When an interface is formed between a metal and a nonreactive (strongly ionic) oxide, interfacial electronic states appear primarily due to three types of interactions. The first effect is the conventional metalinduced gap states (MIGS), which are produced by the exponential decay of delocalized metal states within the insulator. The characteristic of the conventional MIGS is
a structureless continuum of states in the band gap of the oxide substrate. The second cause of interfacial states is the metal−oxygen bonding at the interface. The metal−oxygen
interaction results in donor- and acceptor-like states at welldefined energies located close the valence band maximum (VBM) and the conduction band minimum (CBM) of the oxide. The third effect is the polarization of metal electrons by the electronic field of the substrate. The polarization is analogous to the macroscopic image charge effect. As a result, metal electrons will populate/deplete the space between the deposited metal and the surface cation/anion. The interfacial states from the conventional MIGS and the metal−oxygen hybridization induce charge transfer across the interface creating an interface dipole moment. Polarization of the metal electrons also contributes to the interface dipole moment, although it does not involve any charge transfer across the interface. The work function of the metal and the oxide is shifted according to the direction of the interface dipole moment。


Q1：请问各位老师，其中提到的三种相互作用该怎么理解呢？

Q2：macroscopic image charge effect是指的什么？


Q3：界面偶极矩与功函数之间的关系？


谢谢各位老师指点，