Research Themes
Theme 1
Theme 1: Nanofabrication and Devices
The Institute's research in Nanofabrication and Devices is undertaken by the NEST Group at the University of Canterbury.
Theme Leader: Assoc Prof Steve Durbin
Whilst nanotechnology is tremendously diverse, nanofabrication is the key for engineering nanostructures since it allows precise control over device dimensions and properties. There are two approaches to nanofabrication each with strengths and weaknesses. Traditional “top down” methods are critically constrained by resolution and diffraction limits, and new approaches are needed. Here we will explore such new approaches in areas of optical nanolithography and cluster-based self-assembly where we have proven track records. We will also apply more traditional nanofabrication techniques to new electronic, optical and magnetic devices. Theory and simulation will be used to inform and stimulate our experimental investigations.
- Optical nanopatterning: Controlling light on the nano-scale using near-field and/ or surface plasmon (SP) effects is of great interest, and we have contributed to the development of new new-field optical nanolithography techniques. Nanometre-scale structures showing phenomena such as ‘negative refraction’ and/or ‘superlensing’ are now under intense scrutiny both theoretically and experimentally; our proposed research will extend understanding of superlensing in layered silver films that are predicted to show enhanced resolution, and explore further practical implications of plasmon-assisted near-field lithography alongside out collaborators at MIT. In particular, current efforts include the study of imaging artefacts which arise from the resonant nature of superlens structures.
- Cluster-based assembly and devices: The above lithography-based approach to nanofabrication is complemented by “bottom up” assembly of nano-devices using metal clusters as building blocks. Percolation, template, stencil, and no-lift-off lithography1 based cluster-assembly techniques have been developed and led to the formation of New Zealand’s first nanotechnology company, Nano Cluster Devices Ltd, which has achieved international success. The focus of ongoing work will be the production of reliable transistor structures, and the formation of cluster-assembled devices that are predicted to exhibit fractal conductance fluctuations.
- Semiconductor nanostructures and device fabrication: Our fabrication expertise gives us the ability to branch out into device and applications areas, many of which have strong links into other Themes. Field-emission devices will also be investigated using the ion-beam capabilities at GNS Science. Nanowhiskers of Si grown there exhibit field emission that has shown resonant-tunnelling structure in their IV-curves. Magnetic ions will be implanted in these nanowhiskers to investigate the effect of spin splitting on resonant field emission, creating the possibility of using Si in an emergent semiconductor spintronics technology. In addition, the materials effort in Theme 2 will provide impetus for new nanoelectronic devices. Recent theoretical and experimental work suggests that thermoelectric figures of merit can be improved greatly in nanostructured systems. We are studying the design of low-dimensional semiconductor structures with the goal of simultaneously reducing thermal conductivity and increasing electrical resistivity, building on our previous experience with photovoltaic energy conversion. Additional work includes the study of nitride semiconductor surfaces, and growth of nanostructures–including quantum dots and nanowires–with the ultimate goal of realising electronic devices.
- Theory and modelling: Molecular dynamics simulations have provided critical support to our cluster-based device development, and will focus on complex behaviours and instabilities near the melting point. Our theoretical insight will be applied to design devices that utilise unconventional properties of charge carriers arising from size quantisation, correlations, and spin-dependent effects. Additional work is focussed on addressing the many-body sintering problem in gold nanoparticles, in conjunction with experimental studies.
- Infrastructure and capability: The researchers of the MacDiarmid Institute comprise a large fraction of New Zealand’s capability in nano-science and technology and the fertile environment of the Institute acts as an excellent incubator of ideas and interactions. The nanofabrication and processing resources include facilities for growth (MBE, PLD, UHVcluster deposition), for processing (e-beam and optical lithography, mask aligner, plasma etching) and fi nally characterisation (TEM, SEM AFM, electrical, optical spectroscopy). Our capital infrastructure is of high quality and, very importantly, maintained and operated by skilled technical support staff
- Subwavelength optical lithography (R.J. Blaikie, M. Alkaisi)
- Cluster-based nanoelectronic devices – simulation, fabrication, and characterisation (S.A. Brown, S.C. Hendy)
- Synthesis and characterisation of semi-conductor nanostructures and superlattices (S.M. Durbin)
- STheory of nano-electronic devices and phenomena (U. Zülicke, A.B. Kaiser, A. Markwitz, S.C. Hendy)
- Spin-dependent fi eld emission (A. Markwitz, U. Zülicke)
