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Nanoscience and Nanotechnology |
The properties of nano-scale materials differ significantly from those of their bulk counterparts and the ability to understand, fabricate, manipulate and use such materials has emerged as a critical area of research for the Department. This ranges from studies of metallic and semiconducting nanocrystals and quantum dots to carbon and boron nitride nanotubes.
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C and BN nanotubes
Ying Chen,
Carbon nanotubes are tiny cylinders of graphite sheets with a diameter of a few nanometers. Such one-dimensional structure exhibits many exciting properties and thus regarded as future materials for building nanodevices. Growth of aligned and patterned carbon nanotubes is an important step towards the fabrication of nanotube electronic devices in a large scale. This project will investigate the growth of aligned carbon nanotubes on pre-patterned Si wafer using a mechanically activated chemical vapor deposition method.
Boron nitride (BN) nanotubes have same atomic structure as carbon nanotubes but many interesting properties including a more stable electronic property and better resistance to oxidation at high temperatures. However, BN nanotubes are difficult to be prepared compared with carbon nanotubes. We have developed a unique mechano-thermal process which can produce large quantity and high yield BN nanotubes. We established the first commercial source of BN nanotubes in the world. This project will synthesis BN nanotubes with special structures including cylinders, bamboos and cones.
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Charge storage and dissipation in dielectrics containing nanocrystals
Robert G Elliman, Nawaz Saleh Muhammad
Growth in the use of portable electronic devices and embedded electronic systems has resulted in an increased demand for low-power, high-density non-volatile memory (NVM). However, the scaling of these devices to smaller dimensions is approaching fundamental physical limits and future advances will depend on the use of new materials and greater understanding of limiting processes. A new technique in which the memory is encoded by charged nanocrystals embedded in a high-dielectric constant (high-k) insulating film holds great promise in this regard. This project aims to understand the physical processes underpinning this approach.
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III-V Nanowires
Qiang Gao, Hannah Joyce, H. Hoe Tan, Chennupati Jagadish
Research in this field involves the epitaxial growth of GaAs, InGaAs, InAs, InP and GaSb nanowires on a GaAs and InP of substrates (see epitaxy section). The applications of these nanowires in optoelectronic devices such as nanowire lasers are also investigated.
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Nanorods and Nanowires
Ying Chen, Jun Yu, Jim Williams
New one-dimensional (1D) nanomaterials, such as wires, rods, tubes and belts with diameter less than 100 nm. are a new class of nanomaterials with new or modified material properties due to electron confinement and high-surface-area effects. The single crystalline structure and high surface to volume ratios of the 1D nanomaterials endow them with high stiffness, strength and other new mechanical properties, which lead to applications in reinforced composites, nanosized actuators, force sensors and calorimeters. The new chemical, electronic and magnetic properties of nanowires and nanorods have enormous interests in electronic, sensing and catalytic applications. A large range of nanowires and nanorods of different materials inclduing pure elements (Si, C, and Zn), oxides (ZnO, SiO, and AiSiO), and nitrides and carbides (BN, SiN and SiC) have been made using ball milling and annealing method. In additon, fundamental research in understanding formation mechanisms, in analysing new properties and in exploration of various applications is also conducted in our group. Research projects in the above areas are available for honours students.
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Quantum Dot Optoelectronics
Lan Fu, Ian McKerracher, Greg Jolley, , , H. Hoe Tan, Chennupati Jagadish
Research in this area involves the studies of III-V semiconductor quantum dots (QDs). These studies range from the basic such epitaxy and characterisation of these nanostructures to device applications such as quantum dots lasers and infrared photodetectors (see appropriate sections for more description). We are also investigating the thermal stability and the post-growth interdiffusion/intermixing (by ion implantation and impurity-free vacancy disordering techniques) of the QD structures to selectively modify their bandgaps. This would enable us to integrate devices of differing functionalities onto a single chip.
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Self-assembled growth and doping of optically active silica nanowires
Robert G Elliman, Taehyun Kim, Avi Shalav
There has been an explosion of interest in the synthesis, structure, properties and applications of nanostructures in recent years. This stems from the fact that materials confined in one or more dimension can exhibit novel properties as well as providing the basis for new devices and structures. We have recently been exploring the optical properties of self-assembled silica nanowires grown via a vapour-liquid-solid mechanism and doped with erbium. (Er is a particularly important dopant for many telecommunication-based applications as it emits light at 1.5m, the wavelength of minimum loss in silica-based optical fibres.) This project builds on our preliminary experiments to understand the synthesis, structure, properties and application of these optically active silica nanowires.
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Silicon Based Photonics
Robert G Elliman, , , ,
Research has continued into the properties and applications of Si-nanocrystal-based photonic materials and structures with recent studies examining: a) the effect of impurities on the luminescence intensity and lifetime, b) the effect of materials structure on measured luminescence spectra, c) the fabrication and properties of optical waveguides containing Si nanocrystals, and d) the photoresponse of Si nanocrystals and the prospect of optical gain from such materials.
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