A new spark in nanotechnology

An exciting new artificial material is creating big sparks as it embarks on a revolution in the development of materials for electronic applications, this new superlattice composed of
transition metal oxides was created through the collaborative efforts of European researchers.

Transition metal oxides are an invigorating and relatively new field of science. They first made headlines in 1986 with the Nobel Prize-winning discovery of high-temperature superconductors.
This allows some materials to support superconductivity at temperatures above the boiling point of liquid nitrogen (77 K or -196 C). Apart from superconductivity, transition metal oxides also
have applications in the areas of insulation and semiconducting among others. Because of their diverse application, they also possess the ability to be integrated into numerous devices.

The new superlattice created by the project group consists of a multilayer structure composed of alternating atomically thin layers of two different oxides (PbTiO3 and SrTiO3). This allows the
lattice to possess properties radically different to either of the two materials by themselves. These new properties are a direct consequence of the artificially layered structure and are
driven by interactions at the atomic scale at the interfaces between the layers.

One of the lead researchers on this project, Dr Matthew Dawber, was at the forefront of the effort to make and understand these revolutionary artificial materials in his new lab. ‘Besides the
immediate applications that could be generated by this nanomaterial, this discovery opens a completely new field of investigation and the possibility of new functional materials based on a new
concept: interface engineering on the atomic scale,’ commented Dr Dawber.

Two well-known oxide materials are PbTiO3 and SrTiO3. A theoretical study carried out in Liège predicted that when these materials are combined in a superlattice, an unusual and
completely unexpected coupling between the two types of instabilities occur which is what causes the improper ferroelectricity.

Ferroelectrics can be applied in applications ranging from advanced non-volatile computer memories, to micro-electromechanical machines or infrared detectors. Improper ferroelectricity, is a
kind of ferroelectricity that occurs only rarely in natural materials and usually the effects are far too small to be useful.

A parallel experimental study in Geneva, confirmed the improper ferroelectric character in this type of superlattice, and also provided evidence of an exceptionally useful new property: a
dielectric. This is the ability to simultaneously posses a very high temperature and be independent of temperature Two characteristics that tend to be exclusive of one another but are here
combined in the same material for the first time.

The research group involved the united efforts between the theory group of Professor Philippe Ghosez from the University of Liège, Belgium and the experimental group of Professor
Jean-Marc Triscone based at the University of Geneva, Switzerland.

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