金电极对偶氮苯分子结的结构及其电输运性质的力学调控作用  

Mechanical modulation effects of gold electrodes on geometries and electronic transport properties of azobenzene molecular junctions

作　　者：严岩 孙峰 羊志 孔程昱 葛云龙 陈登辉 邱帅[1] 李宗良[1] Yan Yan;Sun Feng;Yang Zhi;Kong Cheng-Yu;Ge Yun-Long;Chen Deng-Hui;Qiu Shuai;Li Zong-Liang(School of Physics and Electronics,Shandong Normal University,Jinan 250358,China)

机构地区：[1]山东师范大学物理与电子科学学院,济南250358

出　　处：《物理学报》2024年第8期350-358,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11974217,12204281)资助的课题.

摘　　要：偶氮苯分子因存在顺反两种异构体而表现出不同的电输运性质.为了揭示电极的机械作用对偶氮苯分子的几何结构以及电输运性质的影响,基于第一性原理计算研究了偶氮苯分子在电极挤压和拉伸作用下的结构变化规律,并利用非平衡格林函数方法计算了偶氮苯分子结在拉伸和压缩过程中以及分子在不同形状电极之间的电输运性质.结果表明,顺式和反式偶氮苯分子在电极作用下都具有较稳定的几何结构.其中顺式偶氮苯分子在电极拉至超过反式偶氮苯分子结平衡电极距离0.1 nm时仍保持为顺式结构.而反式偶氮苯分子在电极挤压下虽然发生了弯曲,但当电极距离压缩至短于顺式偶氮苯分子结0.2 nm时,中间的C—N—N—C二面角仍然保持反式结构.在低偏压下,两电极若为平面电极,则反式偶氮苯分子的电导高于顺式偶氮苯分子;若分子连接于两锥形电极尖端,则顺式偶氮苯分子结的电导更高.特别值得关注的是两种偶氮苯分子的导电能力随电极距离的变化正好相反,顺式偶氮苯分子结的电导随电极距离拉伸而增大,反式偶氮苯分子结的电导则随电极距离的压缩而增大.偶氮苯分子结的电导在电极距离变化时最大变化幅度可达10倍以上.The azobenzene molecular junction has aroused much interest of scientists due to its switching property arising from its photoinduced isomerism.Owing to the existence of the cis and trans isomers,the electronic transport properties of the azobenzene molecules are promised to show significant differences.The experimental investigations indicate that the cis azobenzene molecule commonly shows high conductance,while the trans azobenzene molecule shows low conductance.However,the computations give the opposite results.To reveal this significant difference,the effects of electrode mechanical modulation on the geometries and electronic transports of the azobenzene molecules are studied.The effects of the electrode geometries on the electronic transports of the azobenzene molecular junctions are also investigated.The electrode compressing process and the electrode stretching process of the azobenzene molecular junctions are simulated based on the first principles calculations.The electronic transport properties are further calculated by using non-equilibrium Green’s function(NEGF)method.The numerical results show that the structures of the cis and trans azobenzenes with sulfur anchors are stable in the stretching process and compressing process of electrode.For the cis azobenzene molecular junction,the cis geometry remains unchanged until the electrode distance is stretched to about 0.1 nm longer than the stable electrode distance of the trans azobenzene molecular junction.Though the trans azobenzene molecule is bent when squeezed by the electrodes,the C—N—N—C dihedral still maintains its trans structure even when the electrode distance is compressed to about 0.2 nm shorter than the stable electrode distance of the cis azobenzene molecular junctions.It is intriguing that the conductance values of cis and trans azobenzene molecular junctions vary inversely with the electrode distance.The conductance value of the cis azobenzene molecular junction increases with the elongating of the electrode distance,while the co

关 键 词：分子器件 偶氮苯分子结 电极距离 分子传感器 

分 类 号：O625.65[理学—有机化学] O646.54[理学—化学]