Microstructural Characterization of Organic Heterostructures by (Transmission) Electron Microscopy

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• 作者：Benedikt Haas ; Katharina I. Gries ; Tobias Breuer ; Ines H盲usler ; Gregor Witte ; Kerstin Volz
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：June 4, 2014
• 年：2014
• 卷：14
• 期：6
• 页码：3010-3014
• 全文大小：333K
• 年卷期：v.14,no.6(June 4, 2014)
• ISSN：1528-7505

文摘

Transmission electron microscopy can be a powerful tool to characterize organic heterostructures, if suitable methods are applied. Here, we present with the example of codeposited films of pentacene (PEN) and perfluoropentacene (PFP) different techniques, which can also be applied to the radiation-sensitive organic materials. The structure and morphology of codeposited films of PEN and PFP on a KCl(100) substrate have been investigated by different (transmission) electron microscopy techniques. When prepared by stoichiometrically equivalent coevaporation of both compounds, the films exhibit an intermixed phase that consists of a 1:1 mixture of the two molecules. Unavoidable excess of one of the two molecules was shown to lead to a spread-out film consisting of the respective molecule, which was verified for the case of PEN excess and whose growth was shown in detail. Interestingly, the film of segregated PEN exhibits a distinctly distinguishable growth from the pure PEN on the same substrate material, forming a 4-fold symmetry aligned with the KCl001 directions. The adaption of an automated nanocrystal orientation and phase mapping technique for the transmission electron microscope, commercially available as the so-called ASTAR system, to these beam-sensitive materials will be discussed as this method not only offers additional functionality for the nanoscale characterization of the films but is inherently advantageous for materials that are prone to beam-induced structural changes.