title: Tuning structural and mechanical properties of two-dimensional molecular crystals: the roles of carbon side chains.
abstract: A key requirement for the future applicability of molecular electronics devices is a resilience of their properties to mechanical deformation. At present, however, there is no fundamental understanding of the origins of mechanical properties of molecular films. Here we use quinacridone, which possesses flexible carbon side chains, as a model molecular system to address this issue. Eight molecular configurations with different molecular coverage are identified by scanning tunneling microscopy. Theoretical calculations reveal quantitatively the roles of different molecule-molecule and molecule-substrate interactions and predict the observed sequence of configurations. Remarkably, we find that a single Young's modulus applies for all configurations, the magnitude of which is controlled by side chain length, suggesting a versatile avenue for tuning not only the physical and chemical properties of molecular films but also their elastic properties.
authors.affiliation: Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Huanyao
authors.initials: H
authors.lastname: Cun
authors.forename: Yeliang
authors.initials: Y
authors.lastname: Wang
authors.forename: Shixuan
authors.initials: S
authors.lastname: Du
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Lizhi
authors.initials: L
authors.lastname: Zhang
authors.forename: Bing
authors.initials: B
authors.lastname: Yang
authors.forename: Xiaobo
authors.initials: X
authors.lastname: He
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: Xueyan
authors.initials: X
authors.lastname: Zhu
authors.forename: Quanzi
authors.initials: Q
authors.lastname: Yuan
authors.forename: Ya-Pu
authors.initials: YP
authors.lastname: Zhao
authors.forename: Min
authors.initials: M
authors.lastname: Ouyang
authors.forename: Werner A
authors.initials: WA
authors.lastname: Hofer
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Pennycook
authors.forename: Hong-jun
authors.initials: HJ
authors.lastname: Gao
mesh_terms: D002244:Carbon / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods; D055119:Elastic Modulus; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; D046911:Macromolecular Substances; C484590:quinacridone; D002244:Carbon