Optical signal from FIB-prepared cross-sections of perovskite thin films
Felix Utama Kosasih a, Giorgio Divitini a b, Jordi Ferrer Orri a c, Elizabeth M Tennyson c, Gunnar Kusch a, Rachel A Oliver a, Samuel D Stranks c d, Caterina Ducati a
a Department of Materials Science & Metallurgy, University of Cambridge, Charles Babbage Road, 27, Cambridge, United Kingdom
b Electron Spectroscopy and Nanoscopy, Istituto Italiano di Tecnologia, 16163 Genova, Italy
c Cavendish Laboratory, Department of Physics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom
d Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
Poster, Giorgio Divitini, 029
Publication date: 3rd April 2023

A strong promise for applications has led hybrid perovskites, beginning from methylammounium lead iodide, to a huge spotlight in global research, leading to a broad variety of chemical compositions. This array of materials yields results competitive with established technologies for solar cells and light emitting devices [1]. The macroscopic properties are strongly influenced by the nanoscale structure, including the morphology, quality of the layers and chemical distribution, which can all be tweaked during synthesis. As devices age, degradation is often triggered due to environmental factors or to operation, and those properties can change further; the understanding of such phenomena is crucial on the quest to viable, robust commercial applications.

Study of the nanoscale properties of hybrid perovskites is often carried out in a transmission electron microscope. To investigate the materials, it is then necessary to prepare them in a suitable format - i.e. as a thin foil up to a few hundred nms in thickness. The process is often carried out using focused ion beam (FIB) milling. [2]. The FIB process is known to significantly affect the sample on the surface and underneath in the case of other materials through amorphisation, implantation of Ga+ ions and local heating, and such effects need to be taken into account for an insightful characterisation. The presented poster [3], reports an evaluation of induced changes by using optical emission as a proxy for the local properties that are relevant to the operation of an optoelectronic device. We carry out spectrally-resolved cathodoluminescence on FIB-prepared lamellae inside an eletron microscope, and correlate the effect of FIB preparation on the surviving luminescent properties of the film.

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