University of Birmingham > Talks@bham > Nanoscale Physics Seminars > Site-dependent ambipolar doping in a silicon surface

Site-dependent ambipolar doping in a silicon surface

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  • UserDr Neil J Curson, Lecturer at the London Centre of Nanotechnology
  • ClockWednesday 25 April 2012, 16:00-17:00
  • HouseWatson Lecture Theatre C.

If you have a question about this talk, please contact Dr. G. Barreto.

Donor atoms in silicon have demonstrated great potential for the fabrication of atomic-scale devices and the implementation of future computation concepts such as quantum information processing (QIP) and spintronics. At the ultimate scaling limit, where device functionality depends on a single atom, dopants will have to be positioned with atomic scale precision in close proximity to gates or other material interfaces. Dopant characteristics will therefore be crucially influenced by abrupt changes in the electronic and structural properties in their atomic scale environment. Furthermore, since solid state QIP proposals are progressively taking advantage of the unique quantum properties of deep group V donors such as bismuth (Bi), the classic model of a dopant representing a shallow impurity in an undisturbed silicon crystal is no longer applicable in its simplest form. To enable the successful implementation of the next generation of electronic devices it is therefore paramount to understand how the characteristics of different group V donor elements interact with their atomic scale environment. Here we use scanning tunnelling microscopy (STM) and density functional theory (DFT) to identify and characterise solitary Bi and antimony (Sb) dopants at the atomic scale. We show that dopants in a silicon surface induce non-local, site-dependent ambipolar charge states, in stark contrast to their bulk counterparts. A model is presented that explains the polarity as well as the location of the observed charges based on newly identified dopant reconstructions. These results not only present a novel approach to localising individual charge carriers at the atomic scale but also demonstrate the crucial importance of understanding the properties of solitary donors when designing future devices based on the precise placement of only a few dopant atoms.

This talk is part of the Nanoscale Physics Seminars series.

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