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研究表明分子器件的性能受器件结构搭建精度影响，分子与电极接触构型的微弱变化可能引起电输运特性较大差异.本文运用密度泛函理论和非平衡格林函数相结合的方法，研究了由金纳米线与benzene-1，4-dithiol（BDT）形成的分子结的电输运性质.通过对不同的Au-BDT接触构型输运性质的研究，发现当两电极处于对位构型时，有较好的电荷输运行为，而且比较符合制备工艺要求；当电极偏离轴线的角度不大于5°，且电极散射截面尺寸不小于4×4时，该分子结体系的电导和透射谱均比较稳定.电极截面尺寸小于4×4或者电极偏离轴线的夹角大于5°时，透射谱在费米能级附近出现不连续现象，导致体系电导降低.较小电极截面尺寸或者电极以较大角度偏离轴线将导致该分子结体系电导降低和透射谱连续性降低，主要是组成电极的金原子轨道与苯基分子轨道耦合缺失造成的.该研究为Au-BDT-Au体系设计和制备过程中电极的位置及电极截面尺寸做了科学的界定.Many investigations indicate that molecular electronics opens up possibilities for continually miniaturizing the electronic devices beyond the limits of the standard silicon-based technologies. There have been significant experimental and theoretical efforts to build molecular junctions and to study their transport properties. The electron transport in molecular device shows clearly quantum effect, and the transport property for molecular device would be strongly affected by chemical and structural details, including the contact position and method between molecule and electrodes, the angle between two electrodes connecting to the molecule. Till now, the micro-fabrication technology still does not guarantee metal electrodes contacting the molecules surfaces ideally. During molecular device fabrication, any tiny variations for the contact configuration usually exist in the molecular device, which would change the device transport property. Hence, it is necessary to investigate the effects of electrode position and electrode cross section size on the transport property.We take Au-benzene-1, 4-dithiol (BDT)-Au (Au-BDT-Au) molecular junctions as example, and systematically calculate its transport properties with various contact positions, and several electrode cross section sizes. The contact face for Au electrode is set to be the (001) face. In the calculations, the density functional theory combined with the Keldysh non-equilibrium Green's function formalism is utilized. The local density approximation is selected as an exchange correlation potential, and atomic core is determined by the standard norm conserving nonlocal pseudo-potential.Our investigations show that the relative position between the electrodes plays a crucial role in the transport behavior of Au-BDT-Au device. When both electrodes are set to be at the counter-position, the preferable transport behavior could be found. The counter-position indicates that the two electrodes are on the same line, which is beneficial to the fabrication. As the angle, which is defined as the angle of electrode deviating from the axis, is larger than five degrees, the transport behavior deteriorates. Hence, the angle for the electrode deviating from its axis should be less than five degrees. To study the effect of electrode cross section size, we calculate the transport properties for three electrode cross sections, i.e. 3×4, 4×4 and 5×4 supercell. Our calculations indicate that when electrode cross section is less than 4×4, the transmission, near the Fermi level, is discontinuous, which would deteriorate the transport performance. Hence, the section size of electrode should not be less than 4×4. This research will provide a scientific index for the electrode position and its cross section size during the fabrication.
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[2] Reed M A, Zhou C, Muller C J, Burgin T P, Tour J M 1997 Science 278 252
[3] Huang J, Li Q X, Yang J L 2016 Sci. Sin. Chim. 46 12 (in Chinese)[黄静, 李群祥, 杨金龙 2016 中国科学: 化学 46 12]
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[29] Zu F X, Zhang P P, Xiong L, Yin Y, Liu M M, Gao G Y 2017 Acta Phys. Sin. 66 098501 (in Chinese)[俎凤霞, 张盼盼, 熊伦, 殷勇, 刘敏敏, 高国营 2017 物理学报 66 098501]
[30] Huang P, Tong G P 2011 J. Zhejiang Normal Univ. (Nat. Sci.) 34 292 (in Chinese)[黄埔, 童国平 2011 浙江师范大学学报(自然科学版) 34 292]
[31] Chen H 2007 Physics 36 910 (in Chinese)[陈灏 2007 物理 36 910]
[32] di Ventra M, Pantelides S T, Lang N D 2000 Phys. Rev. Lett. 84 979
[33] Zou B, Li Z L, Wang C K, Xue Q K 2005 Acta Phys. Sin. 54 1341 (in Chinese)[邹斌, 李宗良, 王传奎, 薛其坤 2005 物理学报 54 1341]
[34] Li Z L, Wang C K, Luo Y, Xue Q K 2004 Acta Phys. Sin. 53 1490 (in Chinese)[李宗良, 王传奎, 罗毅, 薛其坤 2004 物理学报 53 1490]
[35] Xia C J, Fang C F, Hu G C, Li D M, Liu D S, Xie S J 2007 Acta Phys. Sin. 56 4884 (in Chinese)[夏蔡娟, 房常峰, 胡贵超, 李冬梅, 刘德胜, 解士杰 2007 物理学报 56 4884]
[36] Kresse G, Furthmller J 1996 Phys. Rev. B 54 11169
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[1] Aviram A, Ratner M A 1974 Chem. Phys. Lett. 29 277
[2] Reed M A, Zhou C, Muller C J, Burgin T P, Tour J M 1997 Science 278 252
[3] Huang J, Li Q X, Yang J L 2016 Sci. Sin. Chim. 46 12 (in Chinese)[黄静, 李群祥, 杨金龙 2016 中国科学: 化学 46 12]
[4] Park J, Pasupathy A N, Goldsmith J I, Chang C, Yaish Y, Petta J R, Rinkoski M, Sethna J P, Abruña H D, McEuen P L, Ralph D C 2002 Nature 417 722
[5] Nitzan A, Ratner M A 2003 Science 300 1384
[6] Beebe J M, Kim B, Gadzuk J W, Frisbie C D, Kushmerick J G 2006 Phys. Rev. Lett. 97 026801
[7] Chen L, Hu Z, Zhao A, Wang B, Luo Y, Yang J, Hou J G 2007 Phys. Rev. Lett. 99 146803
[8] Chen J, Reed M A, Rawlett A M, Tour J M 1999 Science 286 1550
[9] Dubi Y, di Ventra M 2011 Rev. Mod. Phys. 83 131
[10] Ho G, Heath J R, Kondratenko M, Perepichka D F, Arseneault K, Pezolet M, Bryce M R 2006 Chem. Eur. J. 11 2914
[11] Mujica V, Kemp M, Ratner M A 1994 J. Chem. Phys. 101 6856
[12] Lang N D 1995 Phys. Rev. B 52 5335
[13] Havu P, Havu V, Puska M J, Nieminen R M 2004 Phys. Rev. B 69 115325
[14] Taylor J, Guo H, Wang J 2001 Phys. Rev. B 63 245407
[15] Mads B, Mozos J L, Ordejón P, Taylor J, Stokbro K 2002 Phys. Rev. B 65 165401
[16] Xia C J, Fang C F, Hu G C, Zhao P, Wang Y M, Xie S J, Liu D S 2008 Chin. Phys. Lett. 25 1840
[17] Zhu L, Yao K L, Liu Z L 2009 J. Chem. Phys. 131 204702
[18] Fan Z Q, Chen K Q 2010 Appl. Phys. Lett. 96 053509
[19] Li X F, Chen K Q, Wang L L, Long M Q, Zou B S, Shuai Z 2007 Appl. Phys. Lett. 91 133511
[20] Ren H, Liang W, Zhao P, Liu D S 2012 Chin. Phys. Lett. 29 077301
[21] Fu X, Zhang L X, Li Z L, Wang C K 2013 Chin. Phys. B 22 028504
[22] Zeng J, Chen K Q 2014 Appl. Phys. Lett. 104 033104
[23] Jiang B, Zhou Y H, Chen C Y, Chen K Q 2015 Org. Electron. 23 133
[24] Li Y H, Yan Q, Zhou L P, Han Q 2015 Acta Phys. Sin. 64 057301 (in Chinese)[李永辉, 闫强, 周丽萍, 韩琴 2015 物理学报 64 057301]
[25] Han J, Feng Y, Yao K, Gao G Y 2017 Appl. Phys. Lett. 111 132402
[26] Kuang G W, Chen S Z, Yan L H, Chen K Q, Shang X S, Liu P N, Lin N 2018 J. Am. Chem. Soc. 140 570
[27] Feng Y, Wu X, Han J, Gao G Y 2018 J. Mater. Chem. C 6 4087
[28] Cui Y, Xia C J, Su Y H, Zhang B Q, Chen A M, Yang A Y, Zhang T T, Liu Y 2018 Acta Phys. Sin. 67 118501 (in Chinese)[崔焱, 夏蔡娟, 苏耀恒, 张博群, 陈爱民, 杨爱云, 张婷婷, 刘洋 2018 物理学报 67 118501]
[29] Zu F X, Zhang P P, Xiong L, Yin Y, Liu M M, Gao G Y 2017 Acta Phys. Sin. 66 098501 (in Chinese)[俎凤霞, 张盼盼, 熊伦, 殷勇, 刘敏敏, 高国营 2017 物理学报 66 098501]
[30] Huang P, Tong G P 2011 J. Zhejiang Normal Univ. (Nat. Sci.) 34 292 (in Chinese)[黄埔, 童国平 2011 浙江师范大学学报(自然科学版) 34 292]
[31] Chen H 2007 Physics 36 910 (in Chinese)[陈灏 2007 物理 36 910]
[32] di Ventra M, Pantelides S T, Lang N D 2000 Phys. Rev. Lett. 84 979
[33] Zou B, Li Z L, Wang C K, Xue Q K 2005 Acta Phys. Sin. 54 1341 (in Chinese)[邹斌, 李宗良, 王传奎, 薛其坤 2005 物理学报 54 1341]
[34] Li Z L, Wang C K, Luo Y, Xue Q K 2004 Acta Phys. Sin. 53 1490 (in Chinese)[李宗良, 王传奎, 罗毅, 薛其坤 2004 物理学报 53 1490]
[35] Xia C J, Fang C F, Hu G C, Li D M, Liu D S, Xie S J 2007 Acta Phys. Sin. 56 4884 (in Chinese)[夏蔡娟, 房常峰, 胡贵超, 李冬梅, 刘德胜, 解士杰 2007 物理学报 56 4884]
[36] Kresse G, Furthmller J 1996 Phys. Rev. B 54 11169
[37] Cui B, Zhao W, Wang H, Zhao J, Zhao H, Li D, Jiang X, Zhao P, Liu D S 2014 J. Appl. Phys. 116 073701
[38] Vosko S H, Wilk L, Nusair M 1980 Can. J. Phys. 58 1200
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