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

Lead Research Organisation: University of Cambridge
Department Name: Physics

Abstract

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.

Planned Impact

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.

Publications

10 25 50
 
Description Visiting Professorship - Professor Paul Dastoor
Amount £37,202 (GBP)
Funding ID VP1-2018-027 
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2019 
End 01/2020
 
Title Helium Microscope 
Description The award aims to develop the technique of helium microscopy; we are developing a new instrument while the existing microscope is available for use by others. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? Yes  
Impact In progress. 
 
Title Data supporting A ray tracing method for predicting contrast in atom beam imaging 
Description A ray-tracing method for predicting contrast in atom beam imaging ================================================================= A data-set supporting the publication "A ray tracing method for predicting contrast in atom beam imaging". The experimental data was taken in 2016 as part of an exercise to calibrate the instrument and the simulated data was generated between August 2017 and January 2018. The raw experimental data was gathered by direct digital acquisition from the hardware in Matlab and the simulated data was generated by the code at: https://doi.org/10.5281/zenodo.1228079. MolFlow+ was also used to generate one data set: Molflow+ is a Monte Carlo code developed at CERN by R. Kersevan and M. Ady, website: cern.ch/molflow. The data is split into three parts in three folders: - the experimental data - the simulated data for the images of a tick mark - the simulated data looking at the transmission probability of the detector cone This data packet supports 'A ray tracing method for predicting contrast in neutral atom beam imaging', S.M. Lambrick et. al. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Title Dataset supporting "Multiple scattering in scanning helium microscopy" 
Description The data pack provides helium atom microscope image data for a test sample of FIB-ed trenches in silicon and of an Alvetex scaffold along with simulated ray tracing images for the same test sample. Optical profiler and SEM images are also provided that were used to measure the depth of the trenches. Text description files are included within the archive. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact The data supported the publication "Multiple scattering in scanning helium microscopy", DOI: 10.1063/1.5143950 
 
Title Dataset supporting "Observation of diffraction contrast in scanning helium microscopy" 
Description The data pack provides helium atom microscope image data for lithium fluoride surfaces, demonstrating observation of diffraction contrast. A description of the data format is included within the archive. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact The dataset supports the publication "Observation of diffraction contrast in scanning helium microscopy", DOI: 10.1038/s41598-020-58704-1 
 
Description Collaboration with CNTech Ltd. 
Organisation C N Technical Services
Country United Kingdom 
Sector Private 
PI Contribution We performed neutral helium imaging of samples of metal on silicon substrates and of a silicon sample with trenches milled in to develop a model for potential chemical sensitive contrast in helium microscopy and investigate other contrast mechanisms such as depth sensitivity.
Collaborator Contribution CNTech worked on characterising samples with techniques able to probe the surface roughness on various length scales including white light interferometry, optical profilometry and atomic force microscopy to determine the surface states of the various parts of the sample.
Impact So far images have been included in our publication "Multiple scattering in scanning helium microscopy", DOI: 10.1063/1.5143950
Start Year 2019
 
Description Collaboration with University of Newcastle, Australia 
Organisation University of Newcastle
Country Australia 
Sector Academic/University 
PI Contribution We have established an ongoing collaboration with Prof. Paul Dastoor's group in the University of Newcastle Australia, following on from historic collaboration dating back to development of an initial version of a helium microscope in 2011. The two groups have worked collaboratively to understand contrast in helium images, and to establish applications of helium microscope technology. We were able to support Prof Dastoor in performing helium imaging and atom scattering experiments in Cambridge, to help him understand several existing measurements performed in Newcastle. In addition, we led a major public engagement event at the Royal Society Summer Science exhibition involving both the Cambridge and Newcastle research groups. We supported a programme of public and scientific talks designed to further develop and promote interest in the field of helium microscopy, involving Prof. Dastoor.
Collaborator Contribution During 2019 Newcastle provided extensive contributions in the form of Prof Dastoors direct involvement in Cambridge activities during his year long sabatical visit. Prof Dastoor engaged with a range of ongoing activies, experiments and publications, providing expert scientific expertise and advice. In support of the Royal Society Summer Science exhibition, Newcastle provided direct support of a local postdoctoral researcher for several months, as well as several months of time from a number of Newcastle staff and students, both in Newcastle, and during the exhibition itself in London. Prof Dastoor also supported our activities through a series of public and scientific talks promoting our field.
Impact Several publications have arisen from the longstanding collaboration (listed separately). A commercialisation opportunity is being discussed as a result of the collaboration (details are confidential for now). The collaboration is multidisciplinary, as the technique of helium microscopy can be applied in many areas of science, including physics, chemistry, materials science and biology.
Start Year 2018
 
Description Imaging Diamond Samples 
Organisation De Beers Group
Department Element Six
Country Luxembourg 
Sector Private 
PI Contribution Helium imaging of samples of industrial diamond.
Collaborator Contribution Supply of samples of industrial diamond.
Impact Series of images which will contribute to better understanding of diamond surfaces and diamond wear.
Start Year 2018
 
Description Imaging biological scaffolds 
Organisation Durham University
Department Department of Biosciences
Country United Kingdom 
Sector Academic/University 
PI Contribution We performed neutral helium imaging of biological scaffolds of interest to researchers in the Department of Biosciences at Durham university. We provided those images back to Durham university, thus providing a mechanism for them to image the actual scaffolds of interest in their experimental work, rather than representative samples.
Collaborator Contribution Our partners provided a series of samples, as well as advice on the requirements of their area of research. They also helped draft a paper that includes helium images of the scaffold structure.
Impact So far scaffold images have been included as an example within a related paper, "Multiple scattering in scanning helium microscopy", published in 2020.
Start Year 2019
 
Description Girlguiding Cambs East STEM Day 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact STEM Activity Day organised by Girlguiding Cambridgeshire East. The day consisted of one hour timed sessions, we had a presentation about imaging through history leading to microscopy and the importance of knowing how a sample is affected by the measuring process. We made pinhole cameras using kits that we made in advance and each girl made their own camera and used it to look at bright objects in the environment before taking it home with them. We provided printed and online educational material to link to the GCSE and A-level physics through Isaac Physics and did an augmented reality exercise with the girls using our Augmented reality app. Many of the girls had visible reactions to seeing the effect of light on a sample and understood the principle of the measurement effecting the experiment and thus the result. The connection with being able to make something "that works" connected science and engineering to something that they could do themselves connecting them with cameras and microscope technologies in their lives.
Year(s) Of Engagement Activity 2020
URL http://www.seeingwithatoms.com
 
Description Physics at Work 2018 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Physics at Work is a Department of Physics event, bringing over 2000 students in to experience physics related activities. As part of this award we ran one of the twenty exhibits that students circulate around. Students interest was sparked, engaging them with physics for the future.
Year(s) Of Engagement Activity 2018
URL http://outreach.phy.cam.ac.uk
 
Description Physics at Work 2019 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Physics at Work is a Department of Physics event, bringing over 2000 students in to experience physics related activities. As part of this award we ran one of the twenty exhibits that students circulate around, based on our 2019 Royal Society Summer Science Exhibition stand. Students interest was sparked, engaging them with physics for the future.
Year(s) Of Engagement Activity 2019
URL http://outreach.phy.cam.ac.uk
 
Description Royal Society Summer Science Exhibition 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact The Royal Society Summer Science Exhibition is a major public engagement event run annually in central London, showcasing the best science from UK universities and research organisations. Places at the exhibit are competetively awarded, based on a formal application the year before. Our exhibition showcased the emerging technology of the scanning helium microscope (SHeM) and how it can be applied, including hands on demonstrations, augmented reality exhibits, and live-linkups with researchers in the SHeM labs in Cambridge, UK and Newcastle, Australia. Learning materials were developed in collaboration with Isaac Physics, enabling us to engage directly with teachers and the student curriculum, to consolidate our educational impact. The event enabled us to engage with thousands of students, individually and in school groups, sparking their interest, and providing them with the resources to build upon that spark.
Year(s) Of Engagement Activity 2019
URL http://www.seeingwithatoms.com