Prof Simon Brown, Research Interests
In sufficiently small objects the laws of physics are very different to those in the everyday macroscopic objects we are used to. At the nanoscale, the laws of quantum (rather than classical) physics become important and provide opportunities for many new and exciting fundamental discoveries, as well as building new materials and new novel electronic devices.
This work forms part of the programme of the in the MacDiarmid Institute for Advanced Materials and Nanotechnology.
The research in my group is focused on two main objectives.
Building Electronic Devices with Nanoparticle Building blocks
We use atomic clusters as building blocks for the formation of nano-electronic devices, and explore the novel properties of those devices. Over the past few years we have developed cluster-based devices with applications ranging from chemical sensors to magnetic field sensors to transistors.
We are currently focusing on understanding novel switching behavior in these devices, similar to the behaviour of memristors. We have found that atomic scale wires are formed in tunnel gaps within a percolating film, leading to quantised conductances and cascades of switching events that resemble the learning processes in the human brain. Because the structures are similar to those in the brain, these ‘neuromorphic devices’ show promise for computational tasks (like image processing) that the brain is good at, but which even modern supercomputers find difficult.
- Deposition of Atomic Clusters
- Percolation and Tunneling
- Switching (“Memristor”) effects and Neuromorphic Devices
Exploring novel atomic structures and electronic states in self-assembled nanostructures
We have shown that we can grow many interesting types of nanostructures by simply depositing atoms on to very smooth surfaces and letting them self-assemble. We have focused on growing nanostructures of bismuth and related materials on graphite, and have, for example, shown that they exhibit quantum size effects, where the sizes of the structures are determined by the electronic states inside them. In a new project we are building on this previous work to investigate topological nanostructures grown by similar methods. ‘Topological Insulators’ are one of the hottest topics in physics right now, but very little work has been done on nanostructures.
- UHV scanning probe microscopy
- Deposition of antimony and bismuth onto HOPG
- Scanning Tunneling Microscopy Studies of Topological Nanostructures
November 2015. Marsden Grant Awarded to work on Topological Nanostructures. This new project builds on ten years of experience in growing related nanostructures (see below). The Marsden Fund is New Zealand’s most prestigious science funding agency.
October 2013. New paper published in Physical Review Letters demonstrates quantised conduction and a novel switching phenomenon [Phys. Rev. Lett. 111, 136808 (2013)]
January 2013. Paper in Nano Letters reports novel quantum size effects in the widths of bismuth nanostructures [Nano Letters 13, 43 (2013)].
October 2010. New Grant awarded from the Marden Fund to explore superconductivity and tunneling in percolating tunneling systems of nanoparticles.January / February 2009. New Ultra High Vacuum Scanning Tunneling Microscope / Atomic Force Microscope commissioned.
Past Research Projects
- The structure of atomic clusters.
- Optical studies of Reactive Ion Etched GaN
- Optical studies of amorphous GaN and GaN / AlN superlattices
- Optical studies of many body effects in semiconductor quantum wells.
- Resonant tunneling in high magnetic fields.
- Molecular dynamics simulations of cluster structure