Significantly improved performance of radiation detectors has recently been achieved with lead-halide perovskite single crystals. However, the high lead (Pb) content exceeds the maximum limit set in many jurisdictions (including in the US and UK), and the facile ionic conductivity in these materials limits the range of electric fields that can be applied, thus limiting their operational stability. This proposal will address the challenges of current X-ray detectors, including the use of toxic elements, limited performance, high manufacturing costs, and limited charge-carrier transport. Our preliminary results have shown that BiOI can be the ideal non-toxic alternative to the Pb-based perovskites for next generation radiation detectors because of its high sensitivity and the ability to detect ultralow does rates of X-rays, which arise from its composition of heavy elements, large mobility-lifetime products, and high resistivities. To transfer this technology to industry and to have an impact on medical imaging and nuclear security, we will further 1) improve the mobility-lifetime product to well above 6 +/- 2 x 10^-2 cm2 V-1 s-1 through compositional engineering, 2) increase the size of the detectors by an order of magnitude (from 5 mm currently) without compromising on performance, and 3) optimize the device architecture and imaging performance. The overall aim of this joint research between US team (University at Buffalo) and the UK team (University of Oxford and University of Cambridge) is to develop a new generation of cost-effective, stable and up-scaled bismuth-based radiation detectors capable of detecting three orders of magnitude lower dose rates than the current commercial standard.

Every now and again on Earth a huge volcanic eruption takes place, one much bigger than any that have been experienced by mankind. These have been termed explosive 'super-eruptions'. The most recent really big one was about 75,000 years ago in Sumatra (Indonesia) but previously there were even larger ones than that. They are quite rare, but are the large-scale end of the spectrum of volcanic activity on our planet. They have been quite newsworthy of late, with various programs such as BBC's Super-volcano (aired in summer 2005), based on the Yellowstone eruption about 2 million years ago. These eruptions produce thousands of cubic kilometers (km^3) of magma (molten rock from under the Earth's surface) in huge explosive events that yield volcanic ash beds, more strictly called pyroclastic deposits. One basic problem is that there is so much ash produced, and it is deposited so widely by the violent explosions, that it is quite difficult to trace the products of the eruptions and assess their true size. The largest known eruptions are probably about 5,000 km^3, and the one in Sumatra is estimated to have been about 2,800 km^3 but these estimates are only very rough, and are not accurate to within about half their value. This is not surprising considering that a big eruption in our experience is really very small indeed, such as Mount Pinatubo in 1991 (5 km^3) or Mount St. Helens in 1980 (about 1 km^3)! The proposed study aims, very simply, to determine to a more precise estimate for the volume of one of these vast eruptions that took place about 4 million years ago in the Andes volcanic arc of North Chile. One reason to choose this particular eruption is that the deposits are quite well preserved in the dry, high Atacama desert. Another reason is that this eruption has received some earlier study, including some past work by the Principal Investigator, and it is well enough known to be able to say that it is in the 'Top 5' of the world's largest eruptions, as assessed by a recent survey. However, the various estimates that have been made of its volume, and the way that they have been made, suggest that it could be much larger than presently envisaged. We will use techniques that have not been applied before, including making accurate digital elevation models and mapping the deposits from remotely sensed (satellite) images to try to measure the extent and thickness of the two of the main type of pyroclastic deposit from this eruption. We will also use field-based measurements made directly on the deposits themselves. Another new facet is that we will try to track, for the first time, the widespread, fine volcanic ash bed that must have fallen a long way away from the eruption vents. This may add up, despite its thinness, to a considerable amount more of magma that must have been erupted, and a part that has not been included in previous estimates of the total volume. A local expert collaborator will help us locate these ash beds. Overall, our results will be of interest to anyone interested in the extremes of volcanic activity on Earth, those in the International Association of Volcanology, who are compiling a large-eruption data base, to scientists interested in the environmental impact of explosive volcanism, and to petrologists, who study how magma is generated within the Earth. Basically we want to know 'How big is big?', or at least to know how to better approach making estimates of the size of past eruptions.

The Greenland Ice Sheet (GrIS) has been losing mass over the past three decades and is now a significant contributor to global sea-level rise. In recent decades, the ice sheet's rate of mass (or ice) loss has accelerated, driven by a warming climate and substantial increases both in: 1) the flow speed and retreat rate of many large glaciers that drain the ice sheet and terminate in the ocean; and 2) the surface melt rates and area of the ice sheet experiencing summer melting. However, a critical area of future potential dynamic change and ice-mass loss, which is unaccounted for in our current model projections of the Greenland Ice Sheet's future evolution, concerns the influence of ice-marginal (or proglacial) lake formation on the dynamic stability of outlet glaciers. It is well known from numerous observations elsewhere, that glaciers which terminate in proglacial lakes typically flow much faster than similar sized glaciers that terminate on land. It is now also clear that the number and size of proglacial lakes around the margins of the GrIS are increasing and that trend will continue in to the future. There is therefore the clear potential for the development of more lake-terminating glaciers affecting the ice-sheets' ice-dynamics and long-term stability with the possibility of a dramatic (or 'catastrophic') acceleration in ice-mass loss from these hitherto slowly changing ice-margins. Greenland's land-terminating ice-sheet margins currently flow rather slowly (~100 m/yr) and their mass loss is controlled almost entirely by surface-melt processes. Since the climate is warming, these land-terminating glaciers are thinning and retreating slowly. However, in numerous glaciated regions around the globe, glacier termini are accelerating (by a factor of 2 or more) where glaciers terminate in lakes as opposed to adjacent land-terminating glaciers. This occurs because when a glacier terminates in a lake, it experiences processes which lead to glacier calving, thinning and acceleration. These processes lead to enhanced ice mass loss from the terminus calving and retreat but also through the glacier acceleration which brings ice more rapidly from higher to lower elevations on the ice-sheet thereby exposing the ice to warmer temperatures that promote increased surface melt. As such, a rather simple change in glacier terminus morphology can have a dramatic impact on the glaciers' ice dynamics and mass loss. This project will determine the extent to which these developing proglacial lakes will impact future ice-sheet mass loss, and thus contribute to sea-level rise, over the coming century. We have already undertaken a proof-of-concept study revealing contrasting behaviour at two adjacent lake- and land-terminating glaciers in SW Greenland. Using satellite data to derive glacier velocities, our study shows that ice-motion at the lake-terminating margin more than doubled between 2017-2021 (to ~200 m/yr); by contrast, the neighbouring land-terminating glacier decelerated over the same time-period. We now aim to determine the extent to which these observations of recent acceleration are typical at Greenland's numerous lake terminating margins and more importantly, investigate how important ice-marginal lake terminating glacier dynamics will become in the future for ice-sheet mass loss. In order to achieve this broad aim, the project will use a range of satellite data in conjunction with surface mass balance and ice-sheet modelling to determine: i) how glacier terminus position, motion and surface elevation have changed, both at the ice-margin and inland, in recent decades in response to glacier termination in proglacial lakes; ii) what processes are driving these observed changes in terminus behaviour; and iii) the impact of proglacial lake-induced ice-margin acceleration, thinning and retreat, on the Greenland Ice Sheet's sea level rise contributions, under projected climate warming over the next century.

Pyroclastic density currents (PDCs) are hot avalanches of volcanic rock, pumice, ash and gas that descend the flanks of volcanoes. They can destroy and bury 100's km2 of terrain. Their high temperatures, inherent mobility and unpredictable nature render them one of the most hazardous volcanic phenomena. Since 1600AD, pyroclastic flows have resulted in over 90,000 deaths, 33% of all volcanic fatalities recorded, making them the single biggest cause of death at volcanoes. Forecasting the flow paths and the extent of inundation by pyroclastic density currents at a given volcano depends on our understanding of (i) the flow mechanisms involved (ii) developing models that can faithfully capture the dynamic nature of those flows and accurately simulate past events, and (iii) applying those models probabilistically, so that all possible future scenarios at a given volcano can be considered in order to generate probabilistic hazard maps. Here we will tackle (i) and (ii), but our track history in (iii) demonstrates our longer-term intention. The rationale for this research therefore stems from both a strong end-user defined need, as well as motivation to advance the science of these complex multiphase (particle and gas) natural flows. The aim of this research is therefore to improve the capability of forecasting pyroclastic density current inundation zones around volcanoes by making breakthroughs in understanding the interplay between flow behaviour and how the rheological nature of the flow changes as it propagates. During flow, pyroclastic density currents progressively develop regions that vary in their physical nature and flow mechanisms. Typically, the flows develop high particle concentrations at the base, with frictional or collisional contacts between the particles. An overriding ash cloud develops above this, where particle concentration is low and most particles are supported by turbulent convection of hot gases. As the flows propagate over topography, these upper and lower regions respond differently to changes in slope and valley confinement. Acceleration, deceleration and spreading of the upper and lower units occur at different points, and flow separation can be induced. The propensity for these upper ash clouds to separate from the parent basal flow and travel in unexpected directions often results in lethal consequences. This research will focus on understanding the rheological variations in the basal granular flow and will consider how it may, in turn, modulate mass flux into the overriding ash cloud. We will test the hypothesis that variations in the basal undercurrent rheology, in part induced by topography, result in pore fluid pressure fluctuations that feed the generation and separation of upper turbulent ash clouds from their parent undercurrents. We will achieve this by integrating data obtained from complementary field, geomorphological, experimental and computational studies, in particular utilising cutting-edge modelling tools developed for engineering applications. We will build on important new advances in the understanding of industrial granular flows to characterise how flow rheology varies (through time and space), and what controls those variations. Our results will form the basis for a new constitutive rheology description, providing a fundamental step forward by allowing advance from flow-averaged rheology laws currently employed in flow simulation tools used for hazard quantification. Extensions of this work, in particular the application of the new generation simulation tools will produce hazard maps that have lower associated uncertainties. Using methods we have already developed for probabilistic hazard mapping, we will quantify that degree of improvement. The project is timely and will benefit from synergy with a major Edinburgh-based initiative on industrial granular flows, as well as ongoing research by project partners.

The future of energy-efficient computing will increasingly move from being compute-centric to being memory-centric. There is a huge-energy cost of storing and moving data, which is much higher than computing it. Indeed, memory dominates compute energy (>4X) in data-intensive applications. New ultralow power non-volatile memory (NVM) is central to all aspects of computing, from stand-alone, storage class memory (SCM) for use in data centres, to embedded non-volatile memory (e-NVM) for IoT, the automotive industry, etc, to new forms of computing. The area is growing hugely, along with the associated energy consumption, e.g. data centers will use >10% of global electricity by 2030 with a market growing ~10% per year, to >$150 billion by 2023. Such efficiency cannot come from processing as Moore's law reaches an end and new processor technologies are not yet established. The biggest performance and energy saving gains will be in memory. The replacement of standard memory with high performance memory NVM could reduce power usage by more than 60%. Of the many candidate NVM forms under intense investigation, oxide resistive RAM (RRAM) has the greatest potential in terms of cost, density, simplicity and potential for 3D integration. However, several challenges currently exist, notably the need for a forming voltage, poor uniformity, scaling, and endurance. The aim of this project is to overcome these challenges. It will be done by adopting our ground-breaking results from an ideal system to an industry platform. So far, in the ideal system, we have demonstrated that a) precise and non-random conducting channels can be engineered into films to eliminate the need for a high voltage forming process; b) high and controlled oxygen vacancy concentrations lead to highly and reproducible on-off ratios; c) eliminating use of transition metals produces low leakage and strongly reduces variabilities from film to film. The industry platform we will explore in this project is doped HfO2, grown by sputtering and atomic layer deposition. An internationally leading team with more than 15 years of very strong collaboration in the area of the proposal will undertake the work. First, growth of VAN films using pulsed laser deposition (PLD) will be undertaken at Purdue University. PLD is the simplest way to make the most perfect metal oxide films in a rapid way. These will enable us to understand the RS processes more fully and will provide information on how to grow the films by the industrially scaleable processes. Both Purdue and Cambridge will be involved in the HfO2 nanostructure film design for PLD. The knowledge from the PLD growth will then be translated to the sputtering and ALD approaches undertaken at the University of Cambridge. The effort at the University at Buffalo will focus on the fabrication and testing of prototype memristors and RRAMs using the RS films deposited by Purdue University and University of Cambridge. State-of-the art (some in-operando) characterisation tools will also be central to materials understanding and device optimisation and these will be used at Purdue and Cambridge. A very strong interaction between the groups, with regular sample and knowledge transfer will take place. Our ultimate goal is a forming free device, with on/off ratio~104, endurance >1012, <10pJ per switch, uniformity of few %, scaled to 20 nm. In terms of training, we will educate graduates in materials sciences and electronic engineering. We will train more than 3 early career researchers in world-leading research environments in the US and UK, with several companies involved (small to large), including the Cambridge company ARM who are very active, both in the UK and US, in the memory area.