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J A Venables

Publications and source records attributed to J A Venables.

4 recordsLinked to original sources
PubMed2005

The MIDAS project at ASU: John Cowley's vision and practical results.

An overview of the conception and development of the MIDAS system at Arizona State University is given: a Microscope for Imaging, Diffraction and Analysis of Surfaces. John Cowley's vision in the early 1980s was ambitious and far-reaching, and it was because of him the authors came to ASU. We were centrally involved in the design and implementation of MIDAS from the mid 1980s onwards; the novel design features are briefly reviewed. Practical results obtained using this instrument are listed, and the scope for future development and applications are indicated. While it is clear that many new results have been demonstrated, even more possibilities still remain to be explored. Some comments are made about the feasibility of such developments in the light of competing instrumentation.

Journal Article↗
PubMed2003

Selective nucleation and controlled growth: quantum dots on metal, insulator and semiconductor surfaces.

Nucleation and growth models are well developed for nucleation on homogeneous substrates, and they can typically be described in terms of three energy parameters. Nucleation on substrates containing point-defect traps has been investigated, at the cost of introducing more energy parameters. This paper outlines the quantitative description of such growth models, using rate and rate-diffusion equations, in terms of energies for individual surface processes, with examples taken from metal-metal, metal-insulator and semiconductor growth. The challenge to modelling is to describe the large range of length and time-scales in thin-film fabrication and degradation, without relying on too many (unknown) material parameters, which often occur in combination. Separating them into elementary processes often proves to be a challenge. One typically requires selective nucleation using patterned substrates, in combination with controlled, self-organized, growth for reliable nanotechnology. Reconstructed semiconductor surfaces offer both a further challenge to modelling and an opportunity for future technology; these paradoxes are discussed briefly.

Journal Article↗
PubMed2001

Island nucleation in a reactive two-component system.

The flux and temperature dependence of titanium silicide islands formed by reactive deposition near 500 degrees C indicate a critical nucleus containing 2 Ti atoms and a single activation energy of E(d) + 1/2E(2) = 1.4 +/- 0.2 eV, where E(d) and E(2) are the surface diffusion and cluster binding energies, respectively. These values are not consistent with STM observations of Ti dimer-vacancy hopping at lower temperatures and show that silicide island nucleation involves a different, highly mobile Ti species.

Journal Article↗