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Neil J. Curson
  • Controlled placement and imaging of dopants in semiconductors
  • Study and control of chemical reactions at surfaces
  • Development of scanning probe lithography techniques
  • Fabrication of novel materials by molecular manipulation
 Contact details:
Office: B101
Tel: +44 (0)20 7679 2972
Ext: 32972
Fax: +44 (0)20 7679 0595
Email: n.cursonucl.ac.uk

Research Interest
My prime research interests are centred around understanding and controlling the physics of nano and atomic scale processes that occur at surfaces. This includes fundamental research into the behaviour of atoms and molecules at surfaces and the development and deployment of new nanolithographic techniques, strongly impacting on the fabrication of nanoscale electronic devices and atomic-scale components for quantum computers.

Other activities
This academic year I am teaching the undergraduate course ELEC1011: Circuit Analysis & Synthesis I. I have previously taught the undergraduate course Solid State Physics (PHYS3080) and postgraduate course Advanced Semiconductor Devices (ELEC9501) at University of New South Wales, Australia. I have also developed new undergraduate laboratory experiments i.e. Studying the kinetics of graphite oxidation using a STM - An undergraduate laboratory experiment, N.J. Curson, et al., European Journal of Physics, 20 453 (1999).

Recent Publications

  • S.R. Schofield, N.J. Curson, M.Y. Simmons, L. Oberbeck, T. Hallam, F.J. Rueß and R.G. Clark, Atomically precise placement of single P dopants in silicon, Physical Review Letters, 91 136104 (2003). [PDF file]

Towards the goal of fabricating quantum bits in silicon we have developed a method of controllably placing single P atom dopants into a silicon surface. The method uses a single layer of hydrogen atoms as a resist on the silicon surface. The resist is ‘patterned’ using the tip of a scanning tunnelling microscope, which ‘writes’ by desorbing hydrogen atoms. Phosphine gas (PH3) can then be attached to the written areas. Gently heating the surface causes the P atoms from phosphine to incorporate into the surface, almost exactly where we put them. The implications of this work extend to the microelectronics industry where controlled dopant placement will become important as device dimensions reach the quantum scale. The paper was highlighted in an on-line article by Science Magazine (25th August 2003) and the research is patented worldwide (World Intellectual Patent Organization Publication Number WO/2003/018465).

  • L. Oberbeck, N.J. Curson, T. Hallam, M.Y. Simmons and R.G. Clark, STM imaging of buried P atoms in hydrogen terminated Si for the fabrication of a Si:P quantum computer, Thin Solid Films, 464-465 23 (2004); and
  • F.J. Rueß, L. Oberbeck, M.Y. Simmons, K.E.J. Goh, A.R. Hamilton, T. Hallam, S. R. Schofield, N.J. Curson and R.G. Clark,Towards atomic-scale device fabrication in silicon using scanning probe microscopy,Nanoletters, 4 1969 (2004). [PDF file]

These papers propose and experimentally demonstrate a new approach for fabricating and electrically contacting buried silicon dopant nanostructures. Nanostructures are defined using a hydrogen resist lithography, covered by a thin (25nm) layer of silicon and contacted to the ‘outside world’ so that they can be probed electrically. The first device made was a 90nm wide wire which showed the electrical characteristics of a one dimensional conductor. The research has yielded two patents (WIPO Publication Numbers WO/2005/020139 and WO/2005/019095) and was highlighted in an Editors Choice article in Science (306 1130 2004) and a Research News article in Materials Today Magazine (December 2004). The work was also highlighted by the company Omicron NanoTechnology, in their newsletter Pico (December 2003), as a model demonstration of the application of their product for the development of nanotechnology engineering.

  • S.R. Schofield, N.J. Curson, O. Warschkow, N.A. Marks, H.F. Wilson, M.Y. Simmons, P.V. Smith, M.W. Radny, D.R. McKenzie and R.G. Clark, Phosphine dissociation and diffusion on Si(001) observed at the atomic scale, Journal of Physical Chemistry B, 110 3173 (2006). [PDF file]

Here we demonstrate the use of scanning tunnelling microscopy (STM) to determine surface chemistry processes. We employ hydrogen resist lithography to confine the adsorption of phosphine molecules to nanometre areas of a silicon (001) surface. In the same STM image we can see the structure of a surface covered with molecules and the same surface free from molecular adsorption (because it is protected by the hydrogen resist layer). Thus the registry between the molecular overlayer and the underlying substrate can be ascertained.

Biography

  • Lecturer in Nanotechnology, University College London (2007-present)
  • Senior Research Fellow, University of New South Wales, Australia (2000-2007)
  • Post Doctoral Research Fellow, Cavendish Laboratory, Cambridge, UK (1997-2000)
  • Post Doctoral Research Fellow, Rutgers University, NJ, USA (1996)
  • Ph.D. in Physics, Cavendish Laboratory, Cambridge (1995)
  • B Sc in Physics, University of Leicester (1990)

Research

Describing my research into atomic manipulation with STM to Dr Brendan Nelson, Australian Minister for Defence. (below)
 The controlled incorporation of phosphorus in silicon with atomic-scale precision: STM images show rows of hydrogen terminated silicon dimers. The left cross-hairs show an area where hydrogen has been deliberately removed by the STM tip. After exposing the surface to phosphine gas and heating to 350ºC, a single phosphorus atom is incorporated in the surface, see right cross-hairs. (below)
   
   
These two sequences of STM images show how subtle differences in reaction pathways can drastically effect surface processes. When PH3 adsorbs on a surface it spontaneously dissociates to PH2+H.  Whether the P atom becomes trapped at one place on the surface or is free to wander around depends on whether the PH2 fragment diffuses before falling apart.  (below)
 A device fabricated using atomic force microscope (AFM) lithography. Just (25nm) below the surface of this GaAs wafer is a 2-D sheet of electrons. A narrow 1-D channel is defined in this sheet by local depletion using the AFM. Depletion is achieved by forming an oxide below the tip of the AFM (a process known as local anodic oxidation) and tracing out the lines seen in the image. Electrons travel ballistically through the channel due to their long free mean path in GaAs and form widely spaced sub-bands due to their confinement within the 1-D channel, resulting in unexpectedly high operating temperatures. (below)

(click image to zoom)