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

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.

WHO?
Microscopy has a huge range of applicability and a new form of microscopy has the potential to contribute to active research across the whole spectrum physical and biological sciences, leading in the longer term to both societal and economic impact. In addition to the previous academic beneficiaries, we confidently anticipate impact in the following industrially-relevant fields.

- Semiconductors, electronics and materials for energy: Fabrication is notoriously difficult and delicate. SHeM will provide new opportunities for metrology, including in-situ applications, even during growth. Delicate organic devices in particular can be imaged without destroying functionality; we therefore envisage new approaches to correlating structure with response, ultimately improving the development cycle.

- New polymers and composites: The materials science community will benefit when characterising insulating, charge sensitive and optically active materials, ultimately leading to more sophisticated new materials. Micro-machined polymers, plastics and composites will benefit in particular, especially when involving structures spanning nano- to micron length-scales.

- Device technology: It will be possible to image micro- to nanoscale devices whose structures are difficult to resolve. These include photonic assemblies, devices with quantum functionality, MEMS structures, microfluidic devices and even polymeric medical structures; these typically cannot be conductively coated to enable imaging with charged particles without altering their fundamental characteristics.

- 'Soft' technologies, including biological materials, ices, and waxes that are vacuum compatible can be imaged without preparation or coating. Hence, melting or other damage is avoided without masking surface structure.

- High value samples: Imaging of extremely valuable samples is often avoided due to the risk of damage. SHeM avoids any possibility of beam-induced degradation, mitigating perceived risks and permitting access to unusual specimens such as archaeological artefacts, meteorites, or other irreplaceable items.

- Technology generated will have impact well beyond the immediate field of SHeM. Most notably, the accelerated acquisition and reconstruction methods will benefit the microscopy, remote sensing, image analysis and optical reconstruction.

HOW?
We will engage with as wide a range of potential end-users as possible. Direct collaboration is integral to our strategy: academic groups help showcase the new microscopy, while setting up the proposed microscope as a user-facility extends the audience even further. Academic dissemination will be directed towards conferences and publications with a broad audience: e.g. conferences with delegates from across the sciences. Industrial interest will be nurtured through contributions to community and trade magazines.

Direct links with industry are proposed. We include letters from Element 6, Hitachi and NILT, and will conduct research with them, contributing directly to their R&D. A major goal is to develop a commercial prototype (TRL 6), which will provide much greater access to the technology, benefitting the international scientific community and the UK high-tech economy in general. Cambridge Enterprise will handle IP aspects, and will help establish the most effective route to market, either by licencing, or through an independent spin-out company.

People impacts are also expected. The programme will support training at the undergraduate, postgraduate and postdoctoral levels in both the Universities of Cambridge and Glasgow. Teaching material will be developed for incorporation into courses and student research projects at all levels, leading to long term impact, as individuals develop into future leaders of research. There will be further impact through educational outreach to schools, leveraging our many existing outreach programmes, and drawing on the visual appeal of microscopy.