Bottom-up design of materials using organic building blocks

Physics_colloquium_poster_06-03

Prof. Jennifer MacLeod
Queensland University of Technology

Abstract: One of the goals of nanoscience is achieving precise control over the structure and function of nanoscale architectures at surfaces. Bottom-up approaches using molecular building blocks present a flexible and intuitive approach to this challenge. Combining the Lego-like modularity of molecules with the epitaxial and reactive influences of surfaces creates a range of opportunities to build exciting new nanoarchitectures, which potentially have interesting and/or useful electronic properties.

I will describe two approaches to the fabrication of 1D and 2D organic materials. The first approach is based on self-assembly, which is spontaneous organisation of building blocks via non-covalent interactions. Self-assembled films can be highly-ordered and relevant to, e.g., thin-film organic semiconducting devices. The second approach addresses this point. The second approach involves covalently bonding organic building blocks on a surface, which can create robust materials with tailored electronic properties, I will discuss our recent work in studying the reactions of halogenated and carboxylated molecules at metal surfaces, where we have been focussing on understanding the effect of heteroatoms in the coupling reaction and the subsequent formation of oligomeric and polymeric structures. These studies draw on a combination of scanning tunnelling microscopy, photoelectron spectroscopy and near-edge x-ray absorption fine structure to gain a well-rounded insight into the processes.

The end goal of this work is to establish an understanding of how structure and function are related in these materials. Measuring the electronic properties of organic materials can be challenging, as not many methods offer a way to directly characterise their unoccupied electronic structure. I will provide an overview in our recent work in developing an inverse photoelectron spectrometer optimised for use on organic materials. This instrument, in combination with ultraviolet photoelectron spectrometry, allows us to measure all relevant energy levels in our organic materials.