Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
J Am Chem Soc. 2013 Mar 6;135(9):3680-7. doi: 10.1021/ja3125096. Epub 2013 Feb 20.
The epitaxial growth and preferred molecular orientation of copper phthalocyanine (CuPc) molecules on graphene has been systematically investigated and compared with growth on Si substrates, demonstrating the role of surface-mediated interactions in determining molecular orientation. X-ray scattering and diffraction, scanning tunneling microscopy, scanning electron microscopy, and first-principles theoretical calculations were used to show that the nucleation, orientation, and packing of CuPc molecules on films of graphene are fundamentally different compared to those grown on Si substrates. Interfacial dipole interactions induced by charge transfer between CuPc molecules and graphene are shown to epitaxially align the CuPc molecules in a face-on orientation in a series of ordered superstructures. At high temperatures, CuPc molecules lie flat with respect to the graphene substrate to form strip-like CuPc crystals with micrometer sizes containing monocrystalline grains. Such large epitaxial crystals may potentially enable improvement in the device performance of organic thin films, wherein charge transport, exciton diffusion, and dissociation are currently limited by grain size effects and molecular orientation.
我们系统地研究了铜酞菁（CuPc）分子在石墨烯上的外延生长和优先分子取向，并与在 Si 衬底上的生长进行了比较，证明了表面介导相互作用在确定分子取向方面的作用。X 射线散射和衍射、扫描隧道显微镜、扫描电子显微镜和第一性原理理论计算表明，与在 Si 衬底上生长的相比，CuPc 分子在石墨烯薄膜上的成核、取向和堆积在根本上是不同的。通过 CuPc 分子和石墨烯之间的电荷转移诱导的界面偶极相互作用，使得 CuPc 分子以面外取向在一系列有序超结构中外延排列。在高温下，CuPc 分子相对于石墨烯衬底平躺，形成具有微米尺寸的条状 CuPc 晶体，其中包含单晶颗粒。这种大的外延晶体可能有可能提高有机薄膜器件的性能，其中电荷传输、激子扩散和离解目前受到晶粒尺寸效应和分子取向的限制。
