Full Electrical Control Of The Spin And Valley Degrees Of Freedom In Silicene-based Field Effect Transistor

Since graphene was successfully prepared,many novel two-dimensional materials have been studied in physics and materials science,such as h-BN,molybdenum disulfide and black phosphorus.Silicene,as a graphene-like material,has low-buckled structure.Due to the multiple degrees of freedom for electrons,such as spin and valley,silicene has become one of the hott est frontier objects since its fabrication by Vogt et.al.in 2012.The research on silecene has further promoted the development of concept and application in modern electronics.Based on the latest experimental and theoretical progress in silicene,we design a silicene field effect transistor(FET),and proposes the method of spin-valley all-electrical control.Details are as follows.In chapter 1,we mainly introduce the development,preparation and application of two-dimensional materials,the structure and basic electronic properties of silicene,as well as the experimental and theoretical progress on FET.In chapter 2,we introduce the theoretical methods frequently used in studying the properties of silicene FET,including the effective mass model-Dirac equation,tight binding approximation,Landauer-Buttiker formula,Green function method and density functional theory.In chapter 3,we discuss how to use the anti-ferromagnetic field to achieve independent control of spin and valley in silicene.By using the effective mass of-Dirac equation and Landauer-Buttiker theory,one can prove that valley selective spin filter(VSSF)supporting single valley and single spin transport can be achieved in a silicene FET built by an npn junction,wehre the p doped region exerts an antiferromagnetic field and a vertical electric field.The special VSSF device benefits from an electrically controllable state of the spin polarized single valley Dirac cone.These results obtained are in agreement with previous theoretical and first-principles calculations.In chapter 4,we give a new proposal to realize the full electric control of spin and valley.Through theoretical analysis and numerical calculations,we investigate the spin-valley polarization transport in a ferromagnetic silicene device,where the central region is controlled by an interlayer electric field(Ez),and the valley selective spin polarization filter with 100% valley polarization or spin polarization can be achieved by adjusting the Ez.This study provides an effective way to control the valley and spin simultaneously in future logic circuits.The fifth chapter is the summary and prospect.