一维线性非共轭石墨烯基(CH2)n分子链的电子输运

一维非共轭烷烃链虽不具富电子或少电子特征,但常存在于单分子器件或多肽、蛋白质等生物分子中,对电子传输产生重要影响.为理解这类物质的电子输运特征,本研究设计了一维线性非共轭(CH2)n分子结模型,并利用密度泛函理论结合非平衡态格林函数的方法,对(CH2)n(n=1-12)线性分子链与两个石墨烯电极耦合而成的分子结进行了第一性原理计算.结果表明,CH2分子链随着n值的变化,其电导值表现出明显的奇偶振荡现象,并且随着链长的增加呈指数级的衰减,这一结果与实验研究取得了很好的一致性,为理解和设计性能更加优良的单分子器件提供了重要理论依据.

Electron transport of one-dimensional non-conjugated(CH2)n molecule chain coupling to graphene electrode

Although the one-dimensional non-conjugated alkane chain,which has an important influence on the electron transport process,does not possess the characteristics of electron-rich and electron-deficient,it often exists in single-molecule devices and biological molecules such as peptides and proteins.In order to understand the electron transport characteristics of alkane chain,a one-dimensional linear non-conjugate(CH2)n molecular junction model is designed in this study.Subsequently,we conduct the systematic study of the electronic transport behavior of(CH2)n(n=1-12) molecular linear chain coupling to two graphene electrodes,based on the density functional theory and nonequilibrium Green’s function formalism.The results reveal that the structure and conductance of CH2 chain are highly sensitive to the odevity of CH2 unit.When the value of n is odd,the groups of CH2 extend in a zigzag way from the left electrode to the right electrode in the plane of graphene,while the value of n is even,what is different is that the groups of CH2 are arranged above and below the electrode plane.For this reason,the odd-even behavior of conductance occurs in the(CH2)n(n=1-12)molecular chain.Furthermore,n is also an important factor to affect their transport properties(odd or even behavior of conductance).The longer the(CH2)n chain,the deeper the suppression in transmission spectrum and the lower the equilibrium conductance.What is more,the conductance decreases exponentially with the increase of molecular length,with a decay constant β of 0.67 and 0.60 for odd and even,respectively,which is in good agreement with the experimental research.Additionally,by analyzing their eigenchannels of odd and even(CH2)n molecular chain,we find that the coplanar σ electron with graphene electrode makes a major contribution to the electronic transport channel.The current-voltage curve of(CH2)n molecular chain exhibits nonlinearity,implying their semiconductor characteristics.The interesting mechanical and electronic transport properties are expected to conduce to further experimental synthesis,design and operation of the single molecular nanodevices.