Microscopy with neutral helium atoms: A wide-ranging new technique for delicate samples

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Microscopy is vitally important across a wide range of scientific and technological fields. However, despite the multitude of techniques available, there are many materials that are inaccessible to conventional tools: conventional light microscopy is limited to around micron length-scales; electron microscopy often leads to sample damage or charging; and scanning probe methods (such as atomic force microscopy) are limited to small areas on predominantly flat surfaces. Such problems are particularly acute in the case of delicate materials: for example, organic electronic thin films that are damaged by high-energy electrons, or fine polymer structures, where charging obscures the image.The main aim of this proposal is to develop a revolutionary new technique - Scanning Helium Microscopy (SHeM) - that generates images using a low-energy beam of neutral atoms and so obviates the above problems. The new technique has great potential, but it is essential to improve its spatial resolution and to make it possible for non-specialists to perform helium microscopy easily. The applicants are ideally positioned to lead these developments, by exploiting the technology they developed. The research programme is designed to firmly establish helium microscopy as a cutting-edge research tool. The main themes are:1. To develop a new high resolution microscope that will achieve nanoscale resolution and an imaging rate comparable with scanning probe techniques. The new microscope will make possible a wide range of new experiments. It will be suitable for use by non-specialists and made available to users through a facility-like access model.2. To establish and promote the nascent field of helium-microscopy by performing a broad range of collaborative experiments, spanning multiple applications. These will establish applicability of the technique, and help to develop the imaging modalities required to optimise image contrast arises from a variety of atom-surface scattering mechanisms.3. To develop advanced image collection and reconstruction methods, including making use of the compressibility of natural images, to minimise acquisition time and maximise the information content that can be obtained during any given experimental period. By applying such cutting-edge algorithms to a low-signal scanned probe microscopy for the first time, we anticipate the impact of this theme extending far beyond the present project.The programme is inherently collaborative: the new microscope will be developed and constructed at the Cavendish Laboratory (Physics, Cambridge), supported by nano-fabrication of key components in the Materials Physics group, Glasgow. Researchers in Applied Maths (Cambridge) will develop accelerated imaging methods, while a further series of international collaborators have agreed to provide samples, time and expertise, to explore helium imaging in a diverse range of fields.Microscopy with helium will have impact across a wide range of scientific and technological fields, wherever it is difficult to image delicate samples. Applications that are already foreseen include semiconductor devices, composite materials, organic films and the high aspect-ratio structures used in MEMS devices; but the scope for this new microscopy has yet to be fully explored. Success in the project will lead to the commercialisation of a new imaging technology, the impact of which the UK is uniquely positioned to exploit.