Self-Organized and Cu-Coordinated Surface Linear Polymerization

1. CNMS Staff Science Highlight Self-Organized and Cu-Coordinated Surface Linear Polymerization Scientific Achievement We have demonstrated cryogenic surface-coordinated linear polymerization of phenylacetylene on copper, forming a mesoscale, self-organized “circuit-board’’ pattern of 1D polymer that is hybridized with the surface and exhibits unique electronic properties. Significance and Impact Low-dimensional polymerization can have unexpected and unique products, as well as reaction kinetics highly distinct from the bulk form. Polymerization of technologically relevant phenylacetylene on a copper surface occurs at dramatically lower temperatures than in the bulk and produces a reactive polymerized allene-copper complex. Topological defects and polymerization in such systems can be explored and controlled with single-molecule resolution. e d Research Details • Experiments utilize a home-built scanning tunneling microscope, with temperature range 25-300 K. • First principles computation of molecular orientation, bonding, and electronic structure. • Approach enables opportunities for assembly and polymerization of new molecules beyond existing paradigms . write a, Top, b, Side views of the calculated relaxed conformation for periodic cis-poly(phenylacetylene)s adsorbed on Cu(100). (cyan: carbon; orange: copper; light gray: hydrogen) c, High resolution STM image (lower panel) and the calculated isosurface plot for a section of the polymerized structure (upper panel). d, ‘circuit board’ polymer pattern, stars mark points that bias is applied; e shows subsequent depolymerization. Q.Li, J. Owens, C. Han, B.G. Sumpter, W.Lu, J.Bernholc, V. Meunier, P. Maksymovych,M.l Fuentes-Cabrera, M. Pan,Nature Sci. Rep. DOI:10.1038/srep02102. Work was performed at the CNMS – ORNL, North Carolina University, and Rensselaer Polytechnic Institute.

2. Taming Molecules to Assemble into Linear Polymers Scientific Achievement Small molecules deposited on a flat surface have been discovered to produce a large, self-organized “circuit-board’’ pattern of polymer lines. Significance and Impact Controlling molecular assembly into desired architectures by strong bonds enables high stability and efficient electron transport, both key challenges for electronic circuits made from individual molecules. This work identifies a new route to assembly that occurs at low temperature, accessible to semiconductor manufacturing, yet produces thin metallic wires one molecule in width. The approach enables opportunities for assembly of different molecules beyond existing paradigms, each with potentially useful applications. Research Details An ORNL-built cryogenic scanning tunneling microscope enables the experiments to observe and control the polymerization reaction with single-molecule resolution. When combined with large computer simulations that provide additional information about molecular orientation, bonding, and electronic structure, a comprehensive understanding of the mechanisms at the molecular level can be obtained. write These microscope images show self-organized, linear polymer chains that are one molecule wide, forming a ‘circuit board’ pattern. On the bottom right is a model of the molecular assembly determined by computer simulations. Q. Li, J. Owens, C. Han, B. G. Sumpter, W. Lu, J. Bernholc, V. Meunier, P. Maksymovych, M.l Fuentes-Cabrera, M. Pan, Nature Sci. Rep. DOI:10.1038/srep02102. Work was performed at the CNMS – ORNL, North Carolina University, and Rensselaer Polytechnic Institute.