Cd(0001)基底上并五苯分子单层的结构相变  

Structural transition of pentacene monolayer on Cd(0001)

作　　者：石明霞 刘雷 陶敏龙[1] 孙凯[1] 涂玉兵[1] 赵丽娟 王俊忠[1] SHI MingXia;LIU Lei;TAO MinLong;SUN Kai;TU YuBing;ZHAO LiJuan;WANG JunZhong(School of Physical Science and Technology,Southwest University,Chongqing 400715,China)

机构地区：[1]西南大学物理科学与技术学院,重庆400715

出　　处：《中国科学：物理学、力学、天文学》2018年第11期62-69,共8页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：重庆市研究生科研创新项目(编号:CYS17085)资助

摘　　要：并五苯是一种典型的有机半导体分子,在有机电子学中具有重要的应用价值.本文利用有机分子束沉积与低温扫描隧道显微镜研究了Cd(0001)衬底上并五苯分子的自组装结构,发现了3个温度诱导的结构相变:(1)在室温沉积的条件下,并五苯形成无序排列的分子单层.(2)经过320 K的退火,并五苯单层发生了无序-有序相变,交替排列的两种分子链构成了鲱鱼骨(Herringbone)结构.(3)当退火温度升高至350 K,鲱鱼骨结构转变为一种从未报道过的手性三叶草结构:三个并五苯分子二聚体排列成手性风车结构.(4)进一步增加退火温度至400 K,三叶草结构转变为常见的砖墙(Brick-wall)结构.结合密度泛函理论(DFT)计算,发现并五苯分子两端的电荷密度变化是相反的,表明分子带有电偶极矩.特别有趣的是,并五苯手性三叶草结构的手性可以在STM针尖的电场驱动下从一个对映体转换到另一个对映体.Pentacene is a typical organic semiconductor molecule, which has important application value in organic electronics. In this paper, the two-dimensional self-assembled structures of pentacene on the Cd（0001） surface were investigated by means of organic molecular beam deposition （OMBD） and low-temperature scanning tunneling microscopy （LT-STM）. Three structural transitions induced by temperature were found. （1） Pentacene molecules form a disordered molecular monolayer under the room-temperature deposition conditions. （2） For the disorder monolayer, annealing the sample at 320 K leads to the transition from disordered phase to a well ordered monolayer, in which two kinds of molecular chains with different molecular orientations are alternately arranged, constituting the herringbone structure. （3） When the annealing temperature is increased to 350 K, the herringbone packing transforms into a unique chiral clover structure that has never been reported： three same pentacene dimers arrange into a chiral pinwheel structure. （4） Further increasing the annealing temperature to 400 K, the chiral clover structure transforms into a common and ordered brick-wall structure. With the combination of density functional theory （DFT） calculation, it is found that the change of charge density at both ends of individual pentacene molecule is opposite, which indicates that the each pentacene molecule has the net dipole moment. It is particularly interesting that the organizational chirality of chiral clover structure can be switched from one enantiomer to another driven by the electric filed from a STM tip.

关 键 词：并五苯 扫描隧道显微镜 分子自组装 鲱鱼骨结构 三叶草结构 结构相变 手性相变 

分 类 号：O621.13[理学—有机化学] TN40[理学—化学]