Tight-binding Calculations Of The Structures And Electronic Properties Of Low Dimensional Si-based Materials

Si-based materials play a key role in the semiconductor industry during recent decades.The performance of the SiGe devices is closely correlated with the structures of SiGe alloy materials in different dimensions.Although there are plenty of studies on properties of these SiGe alloy materials,there are still many unknown physical mechanism which has not been explained theoretically.The materials properties are closely related to the atomic arrangement on the surface,and the surface is the important zone where the physical and chemical properties have been changed.Therefore,it is necessary to firstly study the mateirlas surface to study the structures and properties of the bulk phases of these materials in detail.The atomic arrangements on the surface present different patterns from those in the bulk phases,and some atoms may leave lattice positions to decrease the system energy.The research on the atomic arrangement on the surface is the foundation for the knowledge of then materials,and then these enable us to change the mateirls properties.This work presents the simulations for the Si substrates containg 3,4,5,and 6 atomic layers with(001)surfaces on density functional tight binding calculations.The Mulliken charge distribution on the surfaces of the Si substrates is also obtained.Dimer structures are occurred on these surfaces.Moreover,when one Ge atom is placed on different positions on these surfaces,the charge distribution changes on the surfaces are investigated as well s the binding energies.