Prof Simon Brown, Research Interests
My main research interest is in the properties of nanometre scale particles and wires. In particular my group has several pieces of equipment that allow deposition and self assembly of nanoparticles (often called “clusters”) and a new UHV Scanning Tunneling Microscope. We are interested in developing ways of building nano-electronic devices from these clusters, and using the microscope to study the atomic arrangements and behavior of the electrons in nanostructures. Over the past few years we have developed on cluster-based devices with applications ranging from chemical sensors to magnetic field sensors to transistors.
This work forms part of the programme of the The Nanostructure Engineering Science and Technology (NEST) Group at the University of Canterbury, which is engaged in research into the fabrication and properties of a variety of nanometre scale structures. The group has a range of interlinked projects and a wide range of fabrication and characterisation equipment (see also more equipment information here). The group has strong links with researchers in the other main centres of New Zealand as a key Partner in the MacDiarmid Institute for Advanced Materials and Nanotechnology.
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.
This image, which was obtained during commissioning, shows arrangement of atoms on a Si (111) surface.
Physics of Nanoscale Structures
The physics of sufficiently small objects is very different to that of everyday macroscopic objects. At the nanoscale, the laws of quantum (rather than classical) physics become important and a wide variety of new phenomena have been observed. Good examples are the observation of the integral and fractional quantum Hall effects in nanometre thick layers of electrons, which earned Nobel prizes for Klaus von Klitzing (1985), and Stormer, Laughlin and Tsui (1998) respectively. One of the curious features of nanoscale systems is that, as well as exciting fundamental physics, they provide important new electronic and optoelectronic devices. The MOSFET structures used by von Klitzing are very similar to the transistors in a typical personal computer. Alferov, Kroemer and Kilby shared the nobel prize for physics in 2000 for developing semiconductor heterostructures used in high-speed- and opto-electronics, and integrated circuits.
The research in this group is now focused on two main objectives. The first is to use atomic clusters as building blocks for the formation of nano-electronic devices, and to explore the novel properties of those devices. We are currently focusing on superconductivity and switching behavior in these devices. The second is to explore the novel atomic structures and electronic states that are observed in self-assembled nanostructures. Here we are focused on Bi nanostructures grown on graphite.
Main research projects
- Deposition of Atomic Clusters
A schematic of a chain of clusters formed by low energy deposition onto a lithographically modified substrate. By taking advantage of an understanding of certain aspects of percolation theory, and using a carefully designed set of contacts, we are able to ensure that the clusters form a nano-wire like structure.
- Percolation and Tunneling
- Switching (“Memristor”) effects
- UHV scanning probe microscopy
- Deposition of antimony and bismuth onto HOPG
- Molecular dynamics simulations of cluster structure
- Additional Research Interests
Additional Research Interests
- The structure of atomic clusters.
An icosahedral Pb cluster. Note the five-fold symmetry. The structure was calculated using molecular dynamics and atoms with different symmetry positions are labelled with different colours using common neighbour analysis.
- 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.