Theoretical Research, Functional Molecular Assembly Of The Silicon Surface

With the rapid development of modern microelectronic industry, the size of electronic device becomes smaller and smaller. When the thickness of SiO₂ on silicon wafer reaches 0.7nm which is the magnitude of several atoms, SiO₂ will lost its insulating property. So, in molecular electronics area, manufacturing molecular devices by using particular molecules which has special electronic properties becomes more and more popular.In this paper, the interaction of organic molecule, metallic ion and Si surface was studied by using the quantum chemistry method. This will provide fundamentals for the research of reaction mechanism of functional molecule with Si surface and adsorption of metallic ion on Si surface.Density functional theory (DFT) was used to study the following systems:1. Addition reaction mechanism of SiH₃ radical with propylene and acetic acid. By comparison, it can be found that SiH₃ radical is more inclined to react with the terminal unsaturated C atom of propylene, which is consistent with the experimental results.2. The reaction mechanism of organic functional molecule nitrone and its tautomers with Si(100) surface was studied by using DFT method combined with MP2 theory. The results show that, by adopting 1,3-dipolar cycloaddition, H-transfer and [2+2] cycloaddition mechanisms, these molecules can be assembled on the Si surface. The modification of Si surface will consequently change the semiconductor's physical and chemical properties.3. The interactions of Na⁺(H₂O)_n (n=1-6) with clean Si(111) surface were investigated by using hybrid density functional theory (B3LYP) combined with MΦ11er-Plesset second-order perturbation (MP2) methods and CASSCF methods. The studies indicate that, the interactions between Na⁺ cation and the dangling bonds of the Si(111) surface are primarily electrostatic with partial orbital interactions, and the magnitude of the binding energies depends weakly on the adsorption sites and the size of the clusters. When water molecules are present, the interaction between Na⁺ and Si(111) surface weakens and the binding energy has the tendency to saturate.