Professor Tony CullisProfessor Tony Cullis

Professor of Semiconductor Nanocharacterisation

email : a.g.cullis@sheffield.ac.uk

tel: +44 (0) 114 222 5407


MA, DPhil, DSc, FRS

Additional Fellowships of the Institute of Physics, the Royal Society of Chemistry and the Institute of Materials, Minerals and Mining.

BA in Chemistry at Oxford (1968), MA, DPhil in Semiconducting Materials at Oxford (1972), DSc Oxford (1995). Bell Laboratories, Murray Hill, NJ, USA: Member of Technical Staff (1972-1975). Defence Research Agency (Royal Signals & Radar Establishment), Malvern, Worcs: Senior Scientific Officer (1975-1978), Principal Scientific Officer (1978-1983), Senior Principal Scientific Officer (1983-1995).

Department of Electronic & Electrical Engineering, University of Sheffield: Professor (1995-present). Head of Semiconductor Materials and Devices Research Group (1999-present). Director of EPSRC North-Eastern Field Emission Gun Transmission Electron Microscope Facility (1998-present). Director of EPSRC Sheffield Focused Ion Beam Facility (2001-present).

Chairman of SERC MSEC Instrumentation Panel (1988-1993). Chairman of RAL CMF (EBLF) Management Committee (1992-1993). Member of EPSRC Functional Materials College (1997-present). Chairman of `Microscopy of Semiconducting Materials´ Series of International Conferences (1977-present)(see link). Chairman of Electron Microscopy and Analysis Group (Inst Phys) (1980-1982). Chairman of Department of Industry Working Party on Transient Annealing (1981-1984). Coordinating Editor of Elsevier journal Materials Science and Engineering Reports (1994-present). President of Scientific Council of TASC Italian National Laboratory (Trieste)(2001-2004).

Research Publications and Presentations

Professor Cullis has published over 300 refereed scientific papers, has edited 14 books, has presented over 80 invited talks world-wide at conferences, university departments and industrial laboratories and has been granted 6 patents. His published papers have received citations from over 5200 sources in the literature between 1981 and December 2004 (data obtained from ISI Citation Index).

Areas of Materials Study

The main focus of study has been upon the properties of semiconducting materials, determined primarily by use of the transmission electron microscope (TEM) often in conjunction with other advanced analytical methods. Professor Cullis´ principal areas of investigation are described briefly below: recent key work in the area of epitaxy which should be highlighted has involved the mapping of the internal composition of individual quantum dots and the identification of the mechanism of the Stranski-Krastanow epitaxial islanding transition, the latter development providing the solution to an outstanding sixty year mystery.

Impact of semiconductor growth morphology upon relief of heteroepitaxial stress

  • Key demonstration that the Stranski-Krastanow epitaxial islanding transition is controlled by vertical elemental segregation in the initially-formed flat ‘wetting’ layer
  • Measurement of the form of strain waves across epitaxial surface ripple arrays
  • Demonstration that defects form preferentially at highly-strained surface ripple troughs – a new misfit defect formation mechanism

Defect structure and composition of semiconductor heteroepitaxial systems (including growth studies using in situ synchrotron X-ray topography)

  • Direct measurement of 2D composition gradients within individual nanoscale quantum dots
  • Computer atomistic simulation of strains within quantum dots exhibiting nonuniform composition
  • Observation by in situ X-ray studies of unique two-stage activation of epitaxial misfit defects

Nature of lattice disorder and impurity distributions produced by ion implantation and subsequent processing of semiconductors

  • Direct TEM nanoscale measurement of low-energy implanted boron and arsenic distributions in Si, showing errors in standard SIMS profiles
  • Direct observation of nanoscale boron clustering in Si after annealing, under device-relevant doping conditions
  • Demonstration of the unexpected, exceptional stability of AlAs under ion bombardment, permitting fabrication of unique amorphous/crystalline multilayers
  • Invention of iodine ion milling procedure to minimize surface damage in TEM thin specimens

Nanoscale microanalysis by advanced analytical electron microscopy

  • Quantitative measurement of nanoscale Ge segregation in epitaxial SiGe alloy MOSFET channels
  • Additional leading studies already described above

Microscopic morphology and luminescence properties of porous Si

  • Demonstration that quantum-domain crystalline Si nanostructures are responsible for the highly-efficient light emission under excitation
  • Demonstration that crystalline Si nanostructures account for the luminescence of highly oxidized porous Si

Ultra-high speed melt growth phenomena in semiconductors, together with processing techniques

  • Observation of large solubility enhancements for low solubility dopants in Si due to nonequilibrium solute trapping during ultra-rapid solidification
  • Observation and quantitative modelling of constitutional supercooling during ultra-rapid solidification
  • Determination of solidification velocity required to amorphize silicon and correlation with atomic-scale growth processes
  • Demonstration that amorphous silicon melts by a first order phase transition to give an undercooled, normal, low-viscosity liquid and that the amorphous phase is not itself a glassy state
  • Invention of novel light guide diffuser/homogenizer for use with high power laser beams

Study of solid-phase precipitation phenomena in semiconductors

  • Crystallographic identification of ζα-FeSi2 precipitates in Si and elemental As precipitates in GaAs

Study of the structural properties of superconducting films

  • Detailed correlation of Nb3Ge film microstructure with superconducting transition temperature

Preparation of metastable metal substitutional solid solutions and amorphous alloys

  • Preparation of metastable alloy layers in the surface regions of Cu crystals by implantation of Ag, W and Ta ions