Time: 14:45

Location:zaal E

Towards Atomically Precise Silicon Devices in all Three Dimensions

M. Y. Simmons

Centre for Quantum Computer Technology, School of Physics, University of New South Wales, Sydney, NSW 2052, Australia

Over the past five years we have developed a radical new strategy for the fabrication of atomic-scale devices in silicon [1-4]. Using this process we have recently fabricated conducting nanoscale wires [5] with widths down to ~2nm, tunnel junctions [6], arrays of quantum dots in silicon [7] and in plane gated single electron transistors [8]. We will present an overview of the technology and of the unique devices that have been made [9].

In particular the talk will focus on recent low temperature transport measurements of a few-electron P donor based quantum dot in silicon which shows a surprisingly dense spectrum of excited states with an average energy spacing of 100μV. The energy spacing of these features is much too low to be accounted for by the nm-scale lateral confinement of either the dot or the leads. Instead we can explain these resonant features with lifting of valley degeneracy of the dot orbital states and present effective-mass calculations for this strongly confined Si:P system which are in good agreement with experimental findings. We discuss the role of valley splitting in P-donor based silicon dots and present our latest results towards STM-patterned single donor devices wherein the charging energy and the excited state spectrum are consistent with charge transport through the orbital states of a single P-donor.

Finally we will highlight some of the opportunities ahead for novel single atom device architectures and some of the challenges to achieving truly atomically precise devices in all three spatial dimensions [10].

[1] H.F. Wilson et al., Physical Review Letters 93, 226102 (2004).

[2] S. R. Schofield et al., Physical Review Letters 91, 136104 (2003).

[3] K.E.J. Goh et al., Applied Physics Letters 85, 4953-4955 (2004).

[4] F.J. Rueß et al., Nano Letters 4, 1969 (2004).

[5] F.J. Rueß et al., Small 3, 567 (2007); Nanotechnology 18, 044023 (2007);

[6] F.J. Rueß et al., Phys. Rev. B Rapid 85, 121303 (2007); Appl. Phys. Lett. 92, 0521011 (2008).

[7] W. Pok et al., IEEE Transactions on Nanotechnology, 6, 213 (2007);

[8] A. Fuhrer et al., Nano Letters 9, 707 (2009).

[9] M.Y. Simmons et al., Int. J. Nanotechnology 5, 3 (2008).

[10] M.Y. Simmons, Nature Physics, 4, 165 (2008).