On-Surface Ullmann Coupling: The Influence of Kinetic Reaction Parameters on the Morphology and Quality of Covalent Networks
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- 作者：Johanna Eichhorn ; Damian Nieckarz ; Oliver Ochs ; Debabrata Samanta ; Michael Schmittel ; Pawel Jerzy Szabelski ; Markus Lackinger
- 刊名：ACS Nano
- 出版年：2014
- 出版时间：August 26, 2014
- 年：2014
- 卷：8
- 期：8
- 页码：7880-7889
- 全文大小：648K
- ISSN：1936-086X
文摘
On-surface Ullmann coupling is a versatile and appropriate approach for the bottom-up fabrication of covalent organic nanostructures. In two-dimensional networks, however, the kinetically controlled and irreversible coupling leads to high defect densities and a lack of long-range order. To derive general guidelines for optimizing reaction parameters, the structural quality of 2D porous covalent networks was evaluated for different preparation protocols. For this purpose, polymerization of an iodine- and bromine-functionalized precursor was studied on Au(111) by scanning tunneling microscopy under ultrahigh vacuum conditions. By taking advantage of the vastly different temperature thresholds for C鈥揃r and C鈥揑 cleavage, two different polymerization routes were compared 鈥?hierarchical and direct polymerization. The structural quality of the covalent networks was evaluated for different reaction parameters, such as surface temperatures, heating rates, and deposition rates by statistical analysis of STM data. Experimental results are compared to Monte Carlo simulations.