Electrical And Electromechanical Properties Of Quantum Dot Systems

In recent years,two-dimensional(2D)layered nanomaterials have attracted great attention and research.As one of the typical members in the 2D crystalline material,graphene has caused a great sensation in physics and material world because of its unique structural characteristics and outstanding performance.People have been studying it in both experimental and theoretical aspects,it's found that graphene has great application prospects in the development and application of nano-electronic components.Although graphene has become a hot material because of its excellent properties,there is no band gap in graphene,so it can't be modulated well.For this reason,other 2D materials have been found and studied.In 2014,phosphorene,a new 2D semiconductor material,has arouse people's research interest.Compared to graphene,the biggest advantage of phosphorene is that there exists an energy gap and its anisotropy,so it is expected to have great application prospect in the preparation of electronic equipment.The research of phosphorene has just begun recently,people have been exploring it because of its great application potential.In this paper,based on the tight-binding approximation,we studied the energy spectrum of graphene quantum dots and phosphorene quantum dots,mainly studied the influence of the shape,the layer numbers,and the defects etc.,besides,external electric field,magnetic field,and strain are also taken into account.Besides the research on graphene quantum dots and phosphorene quantum dots,we have also studied the application of quantum dots in nanoelectromechanical systems(NEMS)—double quantum-dot shuttle(DQDS),we have mainly studied the electron transport in the classical and quantum DQDS systems.In the first chapter,we have reviewed the research progress and significance of graphene and phosphorene in the past few years.In the second chapter,we have introduced the tightbinding approximation when we study the graphene quantum dots and phosphorene quantum dots.In the third chapter,we have studied the energy states of the triangular graphene quantum dots with zigzag and armchair edges,including the cases of the monolayer,bilayer,and trilayer graphene quantum dots.It is found that we can adjust the number of the zero energy states by changing the number of A-type and B-type carbon atoms in graphene quantum dots,besides,the number of layers of the graphene quantum dots is also the method of changing the zero energy states.In the fourth chapter,we have studied the energy spectrum of the bilayer triangle phosphorene quantum dots,the influence of the size,boundary,and defects has been considered,besides,we also considered the influence of the extra vertical electric field and magnetic field.It is found that we can adjust the bandwidth and band gap by changing these factors.In the fifth chapter,we have studied the energy spectrum of the bilayer hexagon phosphorene quantum dots,in addition to thinking about the influence of the size,boundary,defects,extra electric field,and magnetic field,the effect of strain also be considered.We found that strain can adjust the bandwidth and band gap effectively.In the sixth chapter,we have studied the energy spectrum of the bilayer rectangle phosphorene quantum dots,it is found that the energy spectrum exactly match the landau energy of infinite phosphorene.In the seventh chapter,we have theoretically studied the electric transport properties of double quantum-dot shuttle(DQDS),and discussed the electric transport in the classical shuttle case as well as in the quantum case.Finally,in the last chapter,a short summary and outlook are given.