Science, Technology and Engineering

Dr Chris Pakes

Experimental Condensed Matter Physics

Student Projects: email me to discuss research projects for Honours and Postgraduate degrees. We also host research projects for visiting international students, which may be part of the degree at their home institution.

Research interests encompass surface and device physics in a broad range of materials, directed paricularly to the study of quantum and low-dimensional behaviour on the nanoscale:

Low-dimensional Carbon Electronics

Mesoscopic Superconductivity

Small, low capacitance, Josephson junctions are employed in the development of low-noise Superconducting Quantum Interference Device (SQUID) technology, where we are focussing on the development of devices with sub-100 nm loop dimension for sensitive spin detection.

Phase-slip junctions are an interesting arena for the study of quantum tunneling and have recently gained interest for quantum device applications. Our work in this area focusses on engineering a sub-10 nm Nb nanowire within a device architecture that may form a new quantum current standard.

Polymer electronics

The development of materials for polymer electronics relies on understanding the relationshp between surface transport properties on the nanoscale and an observed insulator-metal transition with increased impurity content. We are studying polymers with surface-conducting properties introduced by the ion implantation of impurity atoms. Atomic force microscopy studies demonstrate that the insulator-metal transition is accompanied by clustering of impurity species to form interconnected grains. These studies are on-going for a variety of polymer-impurity systems.

Silicon Nanoelectronics

Within the Centre for Quantum Computer Technology we are interested in atom-scale silicon devices, fabricated by implantation of a low number of dopant atoms. Studies include the effect of dopant atom implantation on the electronic environment the Si and SiO2 materials, defect spectroscopy in thin SiO2 films, and the modification of silicon nanoelectronic devices by the introduction of a variety of dopant species.

Equipment

We make use of a combination of tools for device fabrication, low-temperature measurement, probe microscopy and electron spectroscopy. Some key facilities that we employ include a UHV-scanning tunneling microscope, metals MBE system, focussed ion beam lithography system, and photoelectron spectroscopy equipment at the La Trobe Centre for Materials and Surface Science and the soft x-ray beam-line of the Australian Synchrotron.

Collaboration

We are a actively engaged in collaborative projects with a number of groups in Europe and Australia. These include the Kavli Institute of Nanoscience (TU Delft, Netherlands), Nottingham Nanoscience Centre (UK), National Physical Laboratory (UK), Nanyang Technological University (Singapore), University of Melbourne, University of New South Wales, CSIRO.

Recent journal publications

• C.I. Pakes, etal, “Work function of hydrogenated diamond surfaces under ion impact”, Surface Science, accepted 28th Jan 2007.
• T.M. Buehler, etal, “Controlled single electron transfer between Si:P dots”, Appl. Phys. Lett., 88, 192101 (2006).
• J.Y. Sze, etal, “Conducting Ni nanoparticles in an ion-modified polymer”, J. Appl. Phys., 98, 66101 (2005).
• V. Millar, etal, “Thin-film resists for registration of single ion impacts”, Nanotechnology, 16, 823 (2005).
• D.N. Jamieson, etal, “Controlled shallow single ion implantation in silicon using an active substrate for sub-20 keV ions”, Appl.Phys.Lett., 86, 202101 (2005).
• C.I. Pakes, etal, “Nanoscale electrical characterisation of trap-assisted quasi-breakdown fluctuations in SiO2”, Appl. Phys. Lett., 84, 3142 (2004).
• L.C.L. Hollenberg, etal, “Single spin readout for buried dopant semiconductor qubits”, Phys.Rev. B., 69, 233301 (2004).
• C.I. Pakes, etal, “Manipulation of single magnetic protein particles using atomic force microscopy”, J.Mag.Magn.Mat., 272-276s, E1232 (2004).
• C.I. Pakes, etal, “Technology computer-aided design Modelling of Single-atom Doping for Fabrication of Buried Nanostructures”, Nanotechnology, 14, 157 (2003).
• C.I. Pakes, etal, “Modelling Single-electron-transistor-based Readout in the Kane Solid-State Quantum Computer”, Nanotechnology, 14, 161 (2003).