Showing papers by "Simon Brown published in 2003"

Coalescence of nanoscale metal clusters: Molecular-dynamics study

Abstract: We study the coalescence of nanoscale metal clusters in an inert-gas atmosphere using constant-energy molecular dynamics. The coalescence proceeds via atomic diffusion with the release of surface energy raising the temperature. If the temperature exceeds the melting point of the coalesced cluster, a molten droplet forms. If the temperature falls between the melting point of the larger cluster and those of the smaller clusters, a metastable molten droplet forms and freezes.

Electrical measurements of nanoscale bismuth cluster films

Abstract: A range of percolating atomic cluster films, with nanoscale overall dimensions, have been studied using a combination of in situ and ex situ electrical transport measurements, together with field emission electron microscopy and atomic force microscopy. Bismuth clusters with mean diameter 20 nm were deposited between electrical contacts defined by electron beam lithography. The morphology of the films can be understood within percolation theory, and the electrical measurements show complex behaviour characteristic of both percolation effects and modification of the cluster films by current flow and by oxidation.

Major Tribunal Decisions in 2002

Abstract: The authors review some of the important decisions of the last year, including those relating to redundancy liabilities, transmission of business, union bargaining fees and the parameters of unprotected industrial action. In their review, the authors note the increasing propensity of industrial actors to opt for legally enforced resolutions ahead of industrially negotiated outcomes. The authors also comment that a failure to have regard to such an increasingly legal approach in industrial relations may hold the potential to unravel corporate and commercial transactions. In concluding, the authors express the view that while some of the pressing legal decisions of 2002 remain unresolved, one certainty is that the role of third party tribunals in abating the increasing trend of legalism will continue to be debated.

Major Tribunal Decisions in 2002

Abstract: The authors review some of the important decisions of the last year, including those relating to redundancy liabilities, transmission of business, union bargaining fees and the parameters of unprotected industrial action. In their review, the authors note the increasing propensity of industrial actors to opt for legally enforced resolutions ahead of industrially negotiated outcomes. The authors also comment that a failure to have regard to such an increasingly legal approach in industrial relations may hold the potential to unravel corporate and commercial transactions. In concluding, the authors express the view that while some of the pressing legal decisions of 2002 remain unresolved, one certainty is that the role of third party tribunals in abating the increasing trend of legalism will continue to be debated.

Measurement of the conductivity exponent in random percolating networks of nanoscale bismuth clusters

Abstract: Nanoscale bismuth clusters, produced in an inert gas aggregation source, have been deposited between lithographically defined electrical contacts. The conductivity exponent, t, of the 2D percolating network of bismuth clusters has been derived from in-situ electrical measurements. It was found to be 1.32/spl plusmn/0.25. This value is comparable with theoretical predictions of t /spl middot/1.3 for 2D random continuum percolation networks.

On the Coalescence of Nanoscale Metal Clusters

Abstract: We study the coalescence of nanoscale metal clusters in an inert-gas atmosphere using constant-energy molecular dynamics. The coalescence proceeds via atomic diffusion with the release of surface energy raising the temperature. If the temperature exceeds the melting point of the coalesced cluster, a molten droplet forms. If the temperature falls between the melting point of the larger cluster and those of the smaller clusters, a metastable molten droplet forms and freezes.

Formation of electrically conducting mesoscale wires through self-assembly of atomic clusters

Abstract: Atomic clusters can be produced in a size range (100nm to 0.5nm) that bridges the gap between the limits of current lithographic fabrication technologies for integrated circuits and the atomic/molecular regime. The work presented here aims to combine established top-down device processing with bottom-up engineered cluster assembly. Conducting cluster deposition and standard optical fabrication techniques have been used to produce wires on a textured (V-grooved) substrate. The lengths of the wires (ranging from 2μm to 1mm) are defined simply by the separation of NiCr/Au contacts. The deposited nanoparticles range in size from 20-100nm and in principle define the width of the nanowire. In-situ conductance measurement allows precise control of the deposition process and the onset of conduction in the wire is readily monitored as a function of deposition time. The effectiveness of the surface templating technique is demonstrated by SEM and AFM imaging carried out after deposition. The surface coverage is seen to vary from 100% at the apexes of the V-grooves used to promote growth of the wire. Self assembly of the nanoparticles leads to completion of a wire between the pre-formed contacts with no possibility of a parasitic conduction path. Wires formed through this technique currently have minimum widths of ~1μm but straightforward extensions of the technique should soon allow nanowire formation.

Formation of nanowires at the percolation threshold in rectangular 2D systems

Abstract: Random deposition of conducting nanoparticles on a flat two dimensional (2D) substrate leads to the formation of a conducting path at the percolation threshold. In sufficiently small systems significant finite size effects are expected. However, in the 2D square systems that are usually studied, the random deposition means that the main effect of small system sizes is that stochastic fluctuations become increasingly large. We have performed experiments and simulations on rectangular 2D nanoparticle films with nanoscale overall dimensions. The sample geometry is chosen to limit stochastic fluctuations in the film’s properties. In the experiments bismuth nanoparticles with mean diameters in the range 20-60nm are deposited between contacts with separations down to 300nm. At small contact separations there is a significant shift in the percolation threshold (pc) and the conducting path formed close to pc resembles a nanowire. Percolation theory describes the experimental onset of conduction well: there is good agreement between predicted and measured values of the power law exponent for the correlation length.