Electron Microscopy

Electron microscopy techniques, including scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), are indispensable tools in materials science. They enable detailed characterization of microstructures, interfaces, crystallographic orientations, and chemical composition across a wide range of length scales—from the microscale down to the atomic level. This multiscale insight is crucial for understanding the structure–property relationships that govern the performance of functional materials and for guiding the design of advanced materials for technological applications.

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Electron microscopy technology available at Jožef Stefan Institute

At the Department for Advanced Materials, we have access to several advanced SEMs and TEMs within Center for Electron Microcopy and Microanalysis (CEMM) at Jožef Stefan Institute:

Jeol JSM-7600F: FEG-SEM with detectors for secondary and backscatter electrons, EDS and EBSD.
Thermo Fisher Verios 4G HP: advanced FEG-SEM with detectors for secondary and backscatter electrons, EDS and STEM.
Thermo Fisher Quanta 650 ESEM: large chamber environmental SEM for work under low vacuum conditions; equipped with detectors for secondary and backscatter electrons and EDX system.
Jeol JEM-2100: conventional TEM, suitable for imaging of nanoparticles, diffraction experiments and in-situ analyses using heating/cooling holders.
Jeol ARM 200CF (located at the National Institute of Chemistry): aberration-corrected STEM with cold FEG, annular detectors for HAADF/ABF imaging, and EELS/EDS for atomic-scale chemical analyses.
Thermo Fisher Spectra 300: state-of-the-art aberration-corrected STEM with a high-brightness electron source, monochromator, advanced detectors for simultaneous HAADF/ABF/BF imaging, segmented detector for iDPC, pixelated detector for 4D-STEM, and integrated EELS and EDS systems for atomic-scale chemical and electronic structure analysis.

Preparation of Samples

Preparation of samples is vital for good results with electron microscopy. At our department, we have expertise for preparation of polished cross-sections for SEM and preparation of electron transparent samples for (S)TEM, from simple application of powders to carbon-coated grids to conventional preparation of ceramics samples by thinning – dimpling and ion-milling to preparation of TEM lamellae using focused ion beam (FIB).

Two microscopes are available for preparation of FIB lamellae:

Helios Nanolab650 (FEI) and
Thermo Fisher Helios 5 UC.

Examples of investigations of various functional materials, where characterization with electron microscopy played a crucial role

Few examples of investigations of various functional materials, where characterization with electron microscopy played a crucial role, are described in the continuation:

1. Transformation mechanism of precursor Bi4Ti3O12 platelets to SrTiO3 platelets for photocatalytic water splitting
2. Correlation between the atomic structure and functional properties of thin films based on relaxor ferroelectrics
3. Microstructure development in lithium lanthanum titanate solid electrolyte

1. Transformation mechanism of precursor Bi4Ti3O12 platelets to SrTiO3 platelets for photocatalytic water splitting

Precursor Bi4Ti3O12 (BIT) platelike nanoparticles prepared by molten salt are transformed into perovskite SrTiO3 platelets under hydrothermal conditions. We used electron microscopy for characterization of precursor particles and products after different stages of transformation. The particles were characterized from microscale to the atomic scale.

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References:

A. Čontala, M.M. Kržmanc, D. Suvorov: Plate-like Bi4Ti3O12 particles and their topochemical conversion to SrTiO3 under hydrothermal conditions. Acta Chimica Slovenica 65 (2018) 630–637. https://doi.org/10.17344/acsi.2018.4286.

M. Maček Kržmanc, N. Daneu, A. Čontala, S. Santra, K.M. Kamal, B. Likozar, M. Spreitzer: SrTiO3/Bi4Ti3O12 Nanoheterostructural platelets synthesized by topotactic epitaxy as effective noble-metal-free photocatalysts for pH-neutral hydrogen evolution. ACS Applied Materials and Interfaces 13 (2021) 370–381. https://doi.org/10.1021/acsami.0c16253

A. Čontala, N. Daneu, S. Gupta, M. Spreitzer, A. Meden, M. Maček Kržmanc: Hydrothermal topotactic epitaxy of SrTiO3 on Bi4Ti3O12 nanoplatelets: understanding the interplay of lattice mismatch and supersaturation. Nanoscale Advances 5 (2023) 3005–3017. https://doi.org/10.1039/d2na00741j

Related projects:

M-Era.Net HarvEnPiez: Innovative nano-materials and architectures for integrated piezoelectric energy harvesting applications. 2017-2020. PI: Marjeta Maček Kržmanc.

M-Era.Net SunToChem: Engineering of perovskite photocatalysts for sunlight-driven hydrogen evolution from water splitting. 2019-2022. PI: Marjeta Maček Kržmanc

Slovenian Research Agency project no. J1-9177: Nanoscale investigations of diffusion controlled topotaxial phase transformations in rutile-corundum host systems. 2018-2022. PI: Nina Daneu.

Responsible researchers:

Dr. Marjeta Maček Kržmanc, Assoc. Prof. Dr. Nina Daneu (STEM analyses)

2. Correlation between the atomic structure and functional properties of thin films based on relaxor ferroelectrics

We have investigated thin films based on Sm-doped Pb(Mg1/3Nb2/3)O3–30PbTiO3 (Sm-PMN-30PT) on TbScO3 substrate with SrRuO3 electrode prepared by pulsed lased deposition (PLD), presented in Figure Xa. These partially strained films exhibit ultra-high energy density of 116 J/cm3 and an efficiency of 73%, along with excellent thermal stability and fatigue-free energy storage properties. The superior properties originate from gradual strain relaxation across the film thickness and strongly disordered slush-like domain structure, consisting of interconnected rhombohedral and tetragonal polymorphic nanodomains around 2–5 nm in size with inclined ‘‘head-to-tail’’ polarization between neighboring domains, as shown by quantitative analysis of atomic-scale HAADF-STEM images.

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Another system that we investigated at our department involves lead-free films based on Sn-doped BaTiO3 on SrTiO3 substrate and LaNiO3 electrode, which represent environmentally friendly alternative to the lead-based materials (Fig. Xb). These films achieve 105 J/cm3 energy density and 80 % efficiency. Also in this system, polar nanodomains (1-3 nm) with slush-like polar structures were confirmed by quantitative evaluation of HAADF-STEM images, whereas the formation and behavior of the slush domains under the influence of local electric field was analyzed by phase field modelling.

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Recently, we also investigated epitaxial strained PMN-PT films on SrTiO3 with SrRuO3 electrode. These films exhibit ultra-high energy storage properties, which were achieved using a synergistic strategy involving large polarization, a giant built-in potential/imprint (five times higher than the coercive field), and AFE like behavior. The structural, chemical, and electrical investigations revealed that these achievements mainly arise from the effects of strain, dipole defects, and chemical composition.

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