缺陷对双层扶手型石墨烯纳米带能隙的影响

Effects of defects on gaps of armchair bilayer graphene nanoribbons

双层扶手型石墨烯纳米带的带宽既能打开能隙也能关闭能隙,但带宽难以在实验中精准调控.在紧束缚模型下,结合格林函数理论,证实线缺陷能够调控同一带宽的双层扶手型石墨烯纳米带能隙.本文计算了双层扶手型石墨烯纳米带在不同缺陷下的能带结构、格点波函数和输运性质.数值计算表明,带宽N=3n+2(n为整数)的金属带可被L≠3m(L为缺陷位置,m为整数)的线缺陷占位能打开能隙,一条A(B)原子线缺陷足以打开AB堆叠金属带能隙.带宽N≠3n+2的半导带可被L=3m的线缺陷占位能关闭能隙.仅增加带宽,也可关闭AA堆叠半导体带能隙,但不能关闭AB堆叠半导体能隙.缺陷的占位能可由栅压调控,这为设计双层石墨烯基量子器件提供了理论支持.

The width of bilayer armchair graphene nanoribbons can either open or close the energy gap,but it is difficult to precisely control the width of ribbons in the experiment. Based on the tight-binding model, combined with the Green’s function formalism,it is confirmed that the line defects can regulate the energy gap with the same ribbon width. It is calculated that energy band structures,lattice wave functions and transport properties of bilayer armchair graphene nanoribbons with different line defects.Numerical results show that the on-site energy of a line defect localized at L≠3m(L is the defect position,m is an integer)may open a gap in a metal band with the ribbon width of N=3n+2(n is an integer). And one A(B)atomic line defect is enough to open the gap in a metal band of AB stacked ribbons. The energy gap in a semiconductor band with ribbon width N≠3n+2 can be closed by the onsite energy of a line defect localized at L=3m. Only increasing the ribbon width can also close the AA stacked semiconductor band gap,but not close the AB stacked semiconductor band gap. The on-site energy of defects can be controlled by gate voltage,which provides theoretical support for the design of bilayer graphene based quantum devices.