Sequential assembly of metal-free phthalocyanine on few-layer epitaxial graphene mediated by thickness-dependent surface potential
Scanning tunneling microscopy (STM), epitaxial graphene, phthalocyanine, self-assembly, electrostatic force microscopy (EFM)
ABSTRACT Due to strong interactions between epitaxial graphene and SiC(0001) substrates, the overlayer charge density induced by the interface charging effect is much more attenuated than that of exfoliated graphene on SiO2. We report herein a quantitive detection of the charge properties of few-layer graphene by surface potential measurements using electrostatic force microscopy (EFM). A minor difference in surface potential is observed to mediate a sequential assembly of metal-free phthalocyanine (H2Pc) on monolayer, bilayer and trilayer graphenes, as demonstrated by scanning tunneling microscopy (STM). In order to understand this, we further executed density functional theory (DFT) calculations which showed higher adsorption energies for Pc on thinner graphenes. In this case, we attribute the unique growth behavior of Pc to its variable adsorption energies on few-layer graphene, and in turn the layer charge variations from the viewpoint of energy minimizations. This work is expected to provide fundamental data useful for related nanodevice fabrications.
Tsinghua University Press
Yabo Gao,Yanfeng Zhang,Jun Ren,Denghua Li,Teng Gao,Ruiqi Zhao,Yanlian Yang,Sheng Meng,Chen Wang,Zhongfan Liu, Sequential assembly of metal-free phthalocyanine on few-layer epitaxial graphene mediated by thickness-dependent surface potential. NanoRes.2012, 5(8): 543–549