Functional oxides for emerging devices
Current research and industry attention on functional oxides are based on their wide range of applications, including memory devices, high-frequency electronics and tuneable microwave devices. The key feature of these devices is the speed of switching, with slow relaxation processes being a main downside to their use. Nano-scale structures of active surfaces and interfaces play a critical role in oxide functionality. In the EU-funded project 'Electron probing of functional oxides' (EPOFO), scientists investigated the interface structural defects of functional oxides in thin-film device configurations, and probed oxygen deficiencies at the interfaces. Furthermore, they experimentally identified and evaluated the space charge distributions arising from these defects that inhibit functional properties at the interfaces and surfaces. Through these activities, EPOFO sought to elucidate the role of structural defects, oxygen deficiencies and space charge distributions in regulating the relaxation processes. To address important issues that govern the performance of functional oxide nanoparticle systems and thin-film heterostructures, the project evaluated transmission electron microscopy (TEM) techniques. TEM data were thoroughly analysed using theoretical calculations. Nanoparticle catalytic functionality is known to be directly linked to the active surface sites taking part in the reaction. Through TEM and electron energy-loss spectroscopy, scientists characterised the surface of oxide perovskite catalysts whose reaction mechanisms remained unknown at that time. The conclusions obtained through density functional theory analysis were important given that these catalysts are the best contenders for replacing the conventional costly metal catalysts. Other project findings concerned the lack of sufficient elastic strain for strong magnetoelectric coupling at the interface of a ferroelectric and a ferromagnetic functional oxide system. Nevertheless, results confirmed a sufficient chemical activity between the two oxides that could lead to synthesising complex engineered interfaces. EPOFO contributed to optimising future engineered oxide structures that can be successfully implemented in future working devices. Nano-scale control of the structures should be useful to further investigate the device speed of switching.
