Electrodeposition of Nanowires and Nanostructures from Supercritical Fluids

Supercritical fluids are potentially highly attractive media for the electrodeposition of metals and semiconductors into complex nanostructures [1].  Supercritical fluids readily penetrate porous and nanoporous structures because they have essentially zero surface tension.  They also have low viscosities and hence show enhanced mass transport rates.  Depending on the choice of electrolyte and solvent they can also have a wide electrochemical window. However these advantages do not come without several disadvantages; their generally low dielectric constants, and the necessity to work in sealed systems at elevated temperature and pressure.  For these reasons the field of electrodeposition from supercritical fluids is still relatively unexplored with very little published work on electrodeposition from single phase supercritical systems.

In order to explore the possibilities of using electrodeposition from supercritical fluids to make sub 20 nm nanostructures and nanostructured devices we have focused on the electrodeposition of a range of p-block elements (Ga, In, Ge, Sn, Pb, Sb, Bi, Se and Te) from supercritical difluoromethane [2]. In this lecture I will present results of our latest results on electrodeposition of these elements from supercritical difluoromenthane, the characterization of the electrodeposited materials, and work on the electrodeposition of sub-20 nm nanowires. I will discuss the experimental systems and novel reagents required to undertake this work, including the development of a simple high pressure, high temperature electrical feedthrough. I will also discuss our progress towards making transistors from supercritical fluid electrodeposited nanowires.

Acknowledgements:This is a contribution from the SCFED Project (www.scfed.net), a multidisciplinary collaboration between the Universities of Southampton, Nottingham and Warwick and is funded by a Program Grant from EPSRC (EP/I033394/1).

References

1. P. N. Bartlett, D. A. Cook, A. L. Hector, W. Levason, G. Reid, W. Zhang, M. W. George, J. Ke and D. C. Smith, “Electrodeposition from supercritical fluids”, Phys. Chem. Chem. Phys.,16(2014)9202-9219.

2. P. N. Bartlett, D. C. Cook, M. W. George, J. Ke,  W. Levason, G. Reid, W. Su and W. Zhang, “Phase behaviour and conductivity study of electrolytes in supercritical hydrofluorocarbons”, Phys. Chem.Chem. Phys., 13(2011)190-198.