Nanodiamond probes and Combined Atomic force microscopy and single defect measurement and spectroscopy
Using precision Atomic Force Microscopy (AFM) combined with single photon confocal microscopy and spectrocopy, we are able to learn a great deal about nanoscale objects (for example nanodiamonds). We are now able to attach nanodiamond to the very tip of an AFM cantilever (image on left) which will enable scanning magnetic field detection. This work is largely supported by the Australian Research Council.
Diamond growth
Our materials fabrication lab is currently under development, and very soon we will have a 650 W microwave plasma assisted Chemical Vapour Deposition (CVD) reactor. We are primarily interested in the growth of nanocrystalline diamond. Using the CVD technique we have the flexibility to adjust many different process parameters. The parameters most interesting to my current line of research are growth time (dictates the crystal size or film thickness), nucleation density (dictates whether the diamond fully covers a substrate or consists of isolated crystallites) and doping (enables the incorporation of "colour centres"). The global aim of QMApp is to understand and develop ways to fabricate single quantum systems. With CVD diamond we can do this by growing isolated nanodiamond crystals containing only one dopant atom.
Diamond integrated with photonic structures
One of the limitations of isotropic emission from a solid state colour centre is that the losses (due to simple geometry) are large. We are investigating the use of photonic crystals and microcavities to couple single photon fluorescence. In doing so, the spontaneous emission rate may be enhanced in a certain direction, and the collection efficiency may be improved.
Diamond single photon sources
Once we grow diamonds which have isolated "colour centres" (for example the Nitrogen-Vacancy (NV) below), we can excite that centre with a laser and collect the fluorescence. Given a unique type of colour centre, with a high quantum efficiency, the centre is a single photon source. That is, during each excitation-emission cycle, the centre will emit one, and only one photon. This effectively enables access to a single quantum state which can be applied in new research areas such as Quantum Information science. The demonstration of diamond growth on optical fibres was made by James Rabeau and colleagues at the University of Melbourne in 2005. This work was patented and is now commercially available through Quantum Communications Victoria.
Optically detected magnetic resonance (ODMR)
We are making use of the high brightness and spin selective optical transitions in the NV centre to optically measure the electron spin resonance properties of a single defect. This is also being extended to study other interesting colour centres in diamond.
Nanodiamonds as fluorescence biomarkers
An exciting new, cross-disciplinary research field involves the use of brightly fluorescing nanodiamonds as biomarkers. There are many challenges in the materials processing and organic chemistry stages in development of robust and bright biolables. QMApp is teamed up with the Department of Chemistry and Biomolecular Science to address some of these challenges. Research in this area, and of this cross-disciplinary nature, is at the cutting edge and one of the most exciting projects we are involved in right now.