Functional Materials

Functional materials are generally characterised as those materials which possess particular native properties and functions of their own. For example, ferroelectricity, piezoelectricity, magnetism or energy storage functions.

Functional materials are found in all classes of materials: ceramics, metals, polymers and organic molecules. Functional materials are often used in electromagnetic applications from KHz to THz and at optical frequencies where the plasmonic properties of metals assume particular importance. Functional materials are also of critical importance in materials for energy such as electro- and magnetocaloric materials, for energy storage and for solar harvesting functions.

Research

The thin film activity in the Department of Materials takes place in two groups:

Physical Electronics and Thin Film Materials

This group is headed by Professor Neil Alford MBE FREng and the main emphasis is on functional oxides. These are materials such as piezoelectrics where the application of a voltage causes a change in dimensions, or ferroelectrics where the application of a voltage causes a change in the relative permittivity. Ferromagnetic materials are used in magnetic storage devices. Recent research into functional materials has been towards combining two or more of these into what is now known as multiferroic materials so for example, a piezolectric “buzzer” is caused by the application of an AC voltage to a piezoelectric material causing it to vibrate. The electric field controls the polarisation, the magnetic field controls the magnetisation and the stress controls the strain. We have compiled a list of microwave dielectric resonator materials and their properties.

Molecular Thin Films

Professor Sandrine Heutz’s group is developing capability in the growth and characterisation of molecular thin films. Molecular materials offer attractive alternatives to inorganics for optoelectronic applications, due to their low cost, low weight and the possibility to modify their properties easily through the insertion of functional groups by chemical synthesis. Their semiconducting character is due to the presence of delocalised π-orbitals, more often C-C double bonds, which leads to a lowering of the bandgap.

The research focuses on commercially available polyaromatic molecules, such as phthalocyanines and perylene derivatives. Those small molecules can be sublimed in the vapour phase, either in vacuum or in a flow of inert gas, leading to the formation of high purity films and self-assembled nanostructures. It is possible to modify the growth conditions (substrate and chamber temperature, flow rate, etc.) to control the film morphological, structural and spectroscopic properties – the typical characteristics of a CuPc film deposited on a glass substrate held at room temperature are shown in figure 2. One of the strengths of the molecular thin films is that they can be deposited onto any substrate including polymers and that flexible complex heterostructures can be formed without the constraints of epitaxy, opening up avenues for plastic electronic and spintronics.

Network and centres 

	Centre for Plastic Electronics The Centre for Plastic Electronics' mission is to actively stimulate new, cutting-edge, high-impact research and to meet Imperial’s strategic intent to harness the strengths and breadth of our research to address the global challenges of climate change, energy and global health and security.
	Centre for Terahertz Science and Engineering (CTSE) Imperial College London hosts a number of THz research activities within the Departments of Materials, Electrical and Electronic Engineering, and Physics.  CTSE collaborates closely with Imperial's Institute of Security Science and Technology.  The Department of Materials at Imperial College London provides a dedicated laboratory for the Centre.