General Physics Colloquium

Title: Spontelectrics: a new form of the solid state

Speaker: David Field, IFA

Abstract:

Condense a gas onto a solid surface, no matter what the surface, and a film may be formed which spontaneously exhibits electric fields in excess of 10⁸ V/m. This very surprising observation was made serendipitously in 2009 [1], whilst attempting to measure charging of molecular films with low energy electron beams, using the ASTRID synchrotron storage ring at Aarhus University. In the period since 2009, this so-called spontelectric effect has become a subject of its own.

The molecular materials of which spontelectric films are composed have one thing in common: the individual species must possess a dipole moment. Other than that, the species are very diverse, ranging over simple hydrocarbons, halocarbons, alcohols, organic formates, benzene derivatives and such simple inorganics as nitrous oxide.

In this review lecture, I will outline and attempt to explain some of the physics which lies behind the rather remarkable properties of spontelectric films, partially reviewed in [2]. I will describe the variation with deposition temperature of the electric field, the presence of the Curie effect, the ability to dial up almost any field structure which you desire, by deposition of spontelectrics one upon the other [3], the effects of dilution of a spontelectrically active species nitrous oxide, in xenon [4] and some recent reflection-absorption infrared spectroscopy (RAIRS) experiments at Heriot-Watt University which independently demonstrate the existence of a powerful electric field within films of nitrous oxide [5]. This will lead on to an outline of some of the counter-intuitive behaviour exhibited by spontelectrics, by which, for example, spontaneous fields may increase with temperature of deposition. It will become apparent that spontelectric behaviour is governed by non-linear, non-local phenomenon through which each part of the film communicates with every other part, to create properties that may be unique in solid state physics.

1. Spontaneous Dipole Alignment in Films of N2O, Balog R., Cicman P., Jones N.C. and Field D., Phys. Rev. Lett., 102, 073003 (2009)

2. Spontaneous electric fields in solid films: spontelectrics. Field D., Plekan O., Cassidy A., Balog R., Jones N.C., Dunger J., Int. Rev. Phys. Chem., 32, 345 (2013)

3. Electric Field Structures in thin Films: Formation and Properties. Cassidy 1., Plekan O., Balog R., Dunger J. and Field D., J. Phys. Chem. A 118, 6615 (2014)

4. Investigations into the Nature of Spontelectrics: Nitrous Oxide diluted in Xenon. Cassidy A., Plekan O, Dunger J., Balog R., Jones N.C., Phys. Chem.Chem.Phys. 16, 23843 (2014)

5. Spontaneously electrical solids in a new light. Lasne J., Rosu-Finsen A., Cassidy A., McCoustra M. R. S. and Field D. Submitted for publication (2015)

Wine and cheese will be served at 4 pm