The development of new photonic and electronic technologies depends on understanding and controlling the electronic structure of materials. Electronics technology currently accounts for over 70% world GDP and is fuelled by a wide ranging fundamental science base. Continued growth of this sector is vital for the future in energy, health and security. As the technology becomes more sophisticated, the underpinning materials become more complex: quantum confinement of electrons and chemical inhomogeneity are used to gain new functionality. Discovering and understanding new materials requires the ability to probe and to correlate electronic and chemical properties on very local scales. The next two decades will see great changes in these technologies as new solutions will be needed to maintain data processing, transfer and storage and to operate at lower power consumption. In photonics, solid-state lighting will transform the urban environment and greatly reduce carbon emission and new materials for photovoltaic devices giving significantly higher efficiency will be a major world focus.
Synchrotron radiation, and in particular soft x-rays directly probe electronic states and chemical bonding enabling local structure to be directly correlated with electronic and photonic performance. The VERSOX facility will directly permit such measurements; moreover it will enable nanoscale size and shape to factored into the understanding of electronic properties, it will represent a unique advanced tool for future materials development. High detection efficiency and precise lateral resolution will enable the study of structure-function relationships in new materials with demanding nanostructured geometries and will enable real-time monitoring of processing steps such as functionalisation and fabrication.
Organic semiconductors are replacing their inorganic counterparts in an increasing number of applications (e.g. displays, photovoltaics (PV), sensors) but there remain challenges in optimising fundamental parameters such as current transport and light absorption/emission and in improving the lifetime and reliability. This is being realised using new molecules and new architectures, in particular using composites and blends . There is also a growing activity in the fabrication of new structures using nanostructured organic and inorganic templates . VERSOX will be able to apply parallel spectroscopies optimised for determining the chemical state of elements such as C, N and O and which directly reveals the nature and density of both occupied and unoccupied states that are responsible for light absorption/emission and charge transport.
The ability to fabricate and probe single molecular layers is important for understanding the fundamental interactions that underpin applications such as precursor decomposition at the earliest stages of thin film growth  and charge transfer in PV cells . The structure of the substrate surface can also be used as a template to form new organic structures that do not form naturally . Soft x-ray spectroscopies at VERSOX will be applied to model systems that isolate key molecule-substrate interactions, as demonstrated for example in the adsorption of thiol molecules to metal surfaces  and fullerene adsorption on semiconductor surfaces . VERSOX has the sensitivity to monitor more complex systems involving new substrate and molecular design in particular using nanostructured and functionalised templates such as self-organised nano-particles, graphene and quasicrystals for the adsorption of a wide range of molecules that are not limited to simple vacuum-depositable films. A further advance is the ability to monitor changes in adsorption, self-organisation and templating as a function of coverage, dosing and temperature.
Organic films and blends
Soft X-ray methods will also be applied to the formation of organic thin films and blends to directly measure chemical bonding and energy band alignment at key interfaces. VERSOX will remove experimental constraints such as long data collection time and ex-situ fabrication to enable entire device structures to be measured, vastly improving throughput and exploration of parameter space. It will also enable organic blends (e.g. small molecule/fullerene, polymer/fullerene and polymer/nanoparticle) to be measured as a function of growth conditions and temperature.
In many photonic devices, the performance of the transparent electrode is a limiting parameter and there is a drive to find alternatives to indium tin oxide (ITO) as the world supply of indium becomes an increasing concern. Transparent semiconductors are also being developed for UV photonics using materials such as oxides, nitrides and diamond. Parallel probes of light emission/absorption and local chemical structure provide essential tools in this quest, especially in relation to impurity or defect states in the bulk of new wide-gap materials.
Oxides are used as transparent conducting electrodes (TCO) in most PV and display technologies and also as active charge/light generation materials in applications such as dye-sensitised solar cells (DSSC). Such devices are often limited by interface issues such as the nucleation of thin PV materials on TCOs during growth and charge transfer across these boundaries. The exploitation of semiconducting oxides and in developing new TCOs require improved understanding of growth and on the interplay between light absorption and conductivity. Soft x-ray methods can for example determine the initial surface reactions during growth , the interface energetics at oxide-thin film interfaces  and have led to a new appreciation of the optical and transport gap of ITO . They have also elucidated the timescale for charge transfer in TiO2/dye interfaces crucial to the operation of DSSCs . The combined VERSOX techniques measuring local bonding, electronic structure, charge transfer and luminescence will be applied to oxide fabrication, surface processing and thin film growth.
Synthetic diamond, as a high quality electronic material and as crystalline nanoparticles, is opening up new applications in electronics and the bio-sciences that can operate in environments where Si devices cannot (e.g high temperature, in-vivo). The diamond surface strongly influences such applications; for example surface conductivity in undoped diamond can be controlled by transfer doping, elucidated using photoemission experiments . Photoemission has also been applied in real-time to demonstrate correlations between conductivity and bonding at diamond interfaces at high temperature . C 1s core level spectra were measured in 1s by parallel and direct electron counting using a laboratory x-ray source; using soft x-rays, this is reduced to 25 ms. VERSOX researchers will apply parallel and in-situ soft x-ray methods to probe interfaces between diamond, nanodiamond and organic molecules for applications in electronics and the bio-sciences.
Graphene is increasingly becoming available in larger areas by methods such as the exfoliation technique developed in the UK, growth from the gas phase using and growth on solid surfaces. Each of these methods are used by VERSOX researchers to understand its growth and modification during for example oxidation and heating for fuel cell application . Graphene also has considerable potential as a transparent conducting substrate for PV applications. Graphene’s optical transparency derives from its reduced dimension in the absorption direction, but retains high conductivity in the growth plane. The VERSOX combination of optical and electron detection will probe both light absorption/emission and electronic structure during processing of graphene films and adsorbate interactions on these surfaces .
Inorganic nanoparticles (clusters quantum dots etc.) offer new opportunities for engineering electronic and photonic materials. The impact of spatial confinement on the quantum scale can hugely modify behaviour, switching on light emission, modifying density of states functions, producing Coulomb blockade. The fact that such functional properties are size dependent and, in principle, controllable makes them central to the quest for new materials systems. There are many application for these quasi zero dimensional solids: medical sensors, quantum computing elements, photovoltaic devices, displays, and catalysts.
Many nanostructures are also light emitters through band-gap or defect processes. Materials systems of interest include metals, silicon, silicon dioxide, diamond, compound semiconductors, oxides and nitrides. The surfaces of nanoparticles can be as influential as the bulk in determining their properties; in fact the majority of atoms in a given nanoparticle may reside on the surface or at the interface with a matrix material For example, surface states can either quench or produce luminescence in excited nanoparticles and the surface functionalisation is a crucial design parameter to ensure correct bonding and charge exchange with the surrounding matrix. Soft x-ray methods are particularly well-suited due to their intrinsic depth sensitivity and selectivity especially where complementary spectroscopic probes are collocated [13,14], SPM is of course a key tool for the characterisation of individual nanostructures and combined with x-ray excitation nanoscale imaging can be extended to the nanoscale .