单分子自旋逻辑门是分子自旋电子学中重要的功能器件之一.本文将两个二苯并四氮杂[14]轮烯钴配合物分子通过碳原子链相连然后再通过碳原子链连接到(4,4)单壁碳纳米管电极以构成单分子自旋逻辑门器件.利用第一性原理方法研究了周围空气分子吸附对所设计单分子自旋逻辑门器件功能性的影响.理论计算结果表明,所设计的单分子器件根据对输入和输出信号定义的不同可以实现AND、NOR或XNOR逻辑运算功能.将其置于空气中时,CO2气体分子的吸附不影响器件的逻辑运算功能.相反,当O2、N2或H2O分子吸附时,器件不再具有上述逻辑运算功能.进一步分析发现,二苯并四氮杂[14]轮烯钴配合物分子与吸附CO2气体分子间相互作用很弱,分子器件费米能级附近的电子态几乎不受影响.然而,二苯并四氮杂[14]轮烯钴配合物分子与O2、N2或H2O分子间相互作用较强,导致分子器件费米能级附近的导电态远离费米能级,从而使自旋向上和自旋向下的电子都不导通,进而使逻辑运算功能失效.研究工作表明,周围空气中的气体分子吸附对单分子器件功能性具有重要影响.
Single-molecule spin logic gates provide fundamental functions and are of importance in the field of molecular spintronics.Here,by using the first-principles method,the effects of ambi-ent gas molecules(CO2,O2,N2,or H2O)on the functional stability of the investigated single-molecule spin logic gate consisting of two serially connect-ed cobalt dibenzotetraaza[14]annulene(CoDBTAA)molecules between single-walled carbon nanotubes(SWCNTs)electrodes,have been theoretically investigated.The calculated results suggest that the investigated spin logic gate can realize AND,NOR,or XNOR logic functions depending on the definition of the input and output signals.It is found that these logic functions are not affected by CO2 adsorption.On the contrary,these logic functions are no longer retained upon O2,N2,or H2O adsorption.Further analysis reveals that the interaction between the CoDBTAA molecule and the CO2 adsorbate is very weak while it is strong for O2,N2,or H2O molecules.Therefore,the electronic states of the logic gate around Fermi energy(EF)are almost unchanged for CO2 adsorption.While the adsorp-tion of O2,N2,or H2O obviously modifies the electronic states around EF.The strong interac-tion between CoDBTAA and these three gas adsorbates drives the conductive electronic states to move far away from EF,resulting in the blocking of both spin-up and spin-down cur-rents and further voiding the logic functions.This work suggests that ambient air has an im-portant effect on the functional stability of single-molecule devices and should be carefully evaluated in the future design of functional single-molecule devices.