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Rich Nonlinear Tomography for advanced materials

Lead Research Organisation: University of Cambridge
Department Name: Materials Science & Metallurgy

Abstract

Abstracts are not currently available in GtR for all funded research. This is normally because the abstract was not required at the time of proposal submission, but may be because it included sensitive information such as personal details.
 
Description The Cambridge part of the grant (PI is at the University of Manchester) has focussed on the development of strain tomography using electron diffraction. We have developed a software suite that has identified some of the key aspects for successful tomographic reconstruction using electron diffraction - and the need for precession electron diffraction - which eliminates out of plane strain and enables the use of the 'transverse ray transform'. Phantoms (simulations) have guided us to establish the optimum workflow for the electron tomography and towards the end of the grant experimental data was acquired and analysed using the workflow developed. That analysis is now being finalised and we plan to submit a definitive paper in the next few months.
Exploitation Route There's no doubt that there remains a pressing need to have methods to determine strain in materials in 3D across many different lengthscales. The Cambridge contribution has been to investigate how electron diffraction can reveal 3D strains at the nanoscale. We have shown how with the correct protocol in place robust and accurate results are possible. Such nanoscale results could be of great benefit to those in the aerospace and manufacturing sectors where disorder and defects are introduced deliberately to generate strain in materials, improving mechanical properties. In the semiconductor industry strain is introduced to alter the electron mobility (in e.g. transistors) and an accurate 3D nanoscale 'map' of the strain in semiconductor structures would be of great value.
Sectors Aerospace

Defence and Marine

Digital/Communication/Information Technologies (including Software)

Electronics

Energy

Environment

Manufacturing

including Industrial Biotechology

Transport
 
Title Research data supporting "Local Nanoscale Phase Impurities are Degradation Sites in Halide Perovskites" 
Description Understanding the nanoscopic chemical and structural changes that drive instabilities in emerging energy materials is essential for mitigating device degradation. The power conversion efficiency of halide perovskite photovoltaic devices has reached 25.7% in single junction and 29.8% in tandem perovskite/silicon cells1,2, yet retaining such performance under continuous operation has remained elusive3. Here, we develop a multimodal microscopy toolkit to reveal that in leading formamidinium-rich perovskite absorbers, nanoscale phase impurities including hexagonal polytype and lead iodide inclusions are not only traps for photo-excited carriers which themselves reduce performance4,5, but via the same trapping process are sites at which photochemical degradation of the absorber layer is seeded. We visualise illumination-induced structural changes at phase impurities associated with trap clusters, revealing that even trace amounts of these phases, otherwise undetected with bulk measurements, compromise device longevity. The type and distribution of these unwanted phase inclusions depends on film composition and processing, with the presence of polytypes being most detrimental for film photo-stability. Importantly, we reveal that performance losses and intrinsic degradation processes can both be mitigated by modulating these defective phase impurities, and demonstrate that this requires careful tuning of local structural and chemical properties. This multimodal workflow to correlate the nanoscopic landscape of beam sensitive energy materials will be applicable to a wide range of semiconductors for which a local picture of performance and operational stability has yet to be established. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
URL https://www.repository.cam.ac.uk/handle/1810/342320
 
Title Research data supporting 'Precipitate nanostructuring that enhances lattice compatibility in a Ti-Fe-Al alloy' 
Description Data includes: Microscope images and a 2D TEM DP (.tif files), X-ray diffraction data (.xy files), STEM data (both image and EDX) (.ser files), and SED data which is a .zspy file contained within a .zip file. 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://www.repository.cam.ac.uk/handle/1810/348562