NANOscientific
Forum Europe 2026

Electrochemical Strain and Strain Waves in Mixed Ionic–Electronic Conductors

Materials exhibiting mixed ionic–electronic conductivity play a central role in emerging technologies, including energy storage, bioelectronic interfaces, and neuromorphic computing. In this talk, I will discuss advanced atomic force microscopy (AFM) techniques for probing coupled ionic and electronic transport processes in these materials under operando conditions.

A key phenomenon in mixed conductors is the generation of local electrochemical strain arising from changes in ionic and electronic concentrations. AFM-based methods are uniquely suited to detect these minute strain responses with high spatial sensitivity, as demonstrated by electrochemical strain microscopy (ESM). I will present representative examples spanning conducting polymers as well as battery cathode and anode materials.

Beyond conventional ESM, I will introduce advanced approaches that combine nanoscale strain measurements with electrochemical impedance spectroscopy, enabling direct access to transport kinetics and dynamic material responses. Finally, I will present the concept of strain wave microscopy, which allows visualization of ionic and electronic transport along mixed-conducting thin films and wires. Together, these methods provide powerful tools for investigating transport phenomena in functional materials across multiple length and time scales. [1–3]

Figure: Schematic illustration of electrochemical strain waves (ESWs) generated in the channel of an electrochemical transistor. ESWs propagate into the device channel through combined charge transport and swelling.

References:

[1] F. Bonafè, J. Ji, S. Fabiano, B. Fraboni, T. Cramer, Small 2025, 10345, 1.

[2] F. Bonafè, M. Bazzani, B. Fraboni, T. Cramer, Nat. Commun. 2025, 16, 2499.

[3] S. Daboss, T. Cramer, N. Franke, B. Fraboni, C. Kranz, J. Microsc. 2025, 1.

2D MoS2-based hybrid materials: structural, electronic and catalytic properties revealed by scanning probe microscopy

The absence of surface dangling bonds in two-dimensional crystals makes the controlled attachment of nanostructures, molecules or atoms particularly challenging. Conventional functionalization strategies often rely on extensive defect creation or harsh chemical treatments to provide anchoring sites; however, these approaches compromise the structural and electronic integrity of the host crystal. In this talk, I will present our recent efforts to develop synthesis strategies that enable the stable functionalization of 2D MoS₂ crystals while preserving their intrinsic properties. These approaches either exploit pre-existing defect sites or allow defect-free attachment of nanostructures and molecules on the MoS₂ surface. The resulting hybrid systems exhibit new structural and electronic features, giving rise to novel properties with potential relevance for catalysis and electronic applications. We employ a combination of scanning probe microscopy techniques, including atomic force microscopy (AFM) and scanning tunneling microscopy (STM), to characterize the atomic and electronic structure of these materials. In addition, scanning electrochemical cell microscopy (SECCM) is employed to map their catalytic activity with spatial resolution down to approximately 100 nm. Together, these techniques can provide a detailed nanoscale picture of how surface functionalization, local structure and electronic properties govern the catalytic behavior of MoS₂-based hybrid materials.

Electrochemistry in a Cage: How Steps, Defects and Molecular Confinement Drives the Solid–Liquid Interface Reactions

Electrochemistry is usually described through macroscopic observables: current, potential, charge transfer and reaction rates. Yet the elementary events that decide whether an electrode remains stable, reconstructs, corrodes, intercalates ions or activates catalytic pathways often take place in a far less ideal world: atomic steps, defects, nanocavities, molecular cages and buried interfacial regions. In this talk, I will argue that nanoscale physical confinement is not a geometrical detail of the electrode surface, but an active variable of electrochemical processes .

Starting from in situ and operando scanning probe microscopy studies at electrified solid–liquid interfaces, I will discuss how EC-AFM, EC-STM and complementary spectroscopies can reveal local transformations that are invisible to spatially averaged electrochemical measurements. Highly oriented pyrolytic graphite will be presented as a model system where anion intercalation, gas evolution, blister formation and subsurface oxidation challenge the classical picture of uniform and reversible graphite intercalation. The same conceptual framework will then be extended to vicinal metal surfaces and molecularly modified electrodes, where steps and terraces can be used to separate chemical driving forces from physical confinement effects.

The broader message is that the next generation of interface science should move beyond simply “imaging electrochemistry” toward engineering the local boundary conditions under which electrochemistry occurs . By combining nanomicroscopy, spectroscopy and controlled interfacial architecture, solid–liquid interfaces can become laboratories where reactivity, degradation and protection are not only observed, but spatially programmed.

Complementary C-AFM/XPS characterisation platform for battery-related materials

M. Hývl ¹, E.Tchernycheva ², R.Dominko ², M.Ledinský ¹

¹ Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Prague 6, Czech Republic

² Kemijski Inštitut, Hajdrihova 19, p.p. 660. SI-1001 Ljubljana, Slovenija

Abstract:

Li-ion batteries (LIBs) and other Li-based battery types (all-solid-state LiS-batteries – LS-SSB) are central to the ongoing energy transition, serving as critical energy storage solutions across various applications. For their further development, however,  the electrode-electrolyte interfaces (EEI) and interphases and their crucial role in battery performance must be further studies and understood. The interphase's development is influenced by charge transfer reactions occurring at the EEI, which can trigger various degradation processes. While there is considerable understanding of anode-electrolyte interphases (SEI), the mechanisms behind cathode-electrolyte interphases (CEI) are less explored. This knowledge gap is partly due to the lack of effective techniques for characterizing CEI properties at different scales and conditions. The stability of cathode active materials at the EEI in the selected electrolyte directly correlates with battery cell performance and its cycle life. With most current applications relying on liquid electrolytes and emerging alternatives featuring solid polymer electrolytes, achieving a more comprehensive understanding of the CEI formation processes at micro- and nanoscales is crucial for making progress towards more stable battery performance.

X-ray photoelectron spectroscopy (XPS), has been heavily utilized to study both SEI and CEI due to its ability to detect both chemical composition and chemical oxidation states of the elements present at the very surface and up to the thickness of ~10 nm, with the spatial resolution from ~1 mm to ~10 microns. At its highest resolution, it can overlap with Atomic Force Microscopy (AFM). AFM techniques, such as C-AFM and C-AFM Topography, have enabled substantial advances in understanding the tight relationship between surface topography, electric current and mechanical properties.

In my presented research, I will demonstrate the results and lessons learned from the process of establishing the complementary C-AFM/XPS characterization platform. AFM measurements taken in the protective Argon atmosphere can be correlated with XPS measurements in order to access additional information not available by other characterization techniques, providing much-needed tool for multi-scale in-depth analysis of the EEI.

Beer–Lambert Law at the Nanoscale via Quantitative Infrared Nanospectroscopy

Masbah Ul Hakim,¹ Francesco Simone Ruggeri,¹

¹Physical Chemistry and Soft Matter, Wageningen University & Research – Wageningen, The Netherlands (masbah.hakim@wur.nl, simone.ruggeri@wur.nl)

Abstract:

Quantifying molecular properties of materials at the nanoscale is essential for understanding functional interfaces, where small variations in film thickness, molecular organization and surface coverage can strongly influence material properties. Infrared spectroscopy is widely used for chemical analysis, identifying chemical groups through their characteristic vibrations. At the macroscopic scale, the Beer–Lambert law extends this capability to quantification by relating absorbance to the amount of absorbing material [1]. At the nanoscale, however, this scaling remains untested, because conventional infrared spectroscopy lacks the spatial resolution and sensitivity to probe molecular islands only a few nanometres thick. This leaves a fundamental open question: does Beer–Lambert scaling hold for molecular films of nanometre thickness? Answering this question is essential, because it determines whether nanoscale infrared spectroscopy can move beyond chemical identification toward quantitative measurement of local molecular content.

Here, we test whether Beer–Lambert law persists at the molecular scale by quantifying the infrared response of supramolecular films of well-defined nanometre heights. As a model system, we use self-assembled C16-benzene-1,3,5-triscarboxamide (C16-BTA) molecular films, which form laterally homogeneous crystalline islands with discrete molecular heights [2], as independently determined by atomic force microscopy. Using infrared absorption nanospectroscopy (AFM-IR), which combines molecular specificity with nanometre spatial resolution down to single-molecule sensitivity [3,4], we probe C16-BTA assemblies of different molecular heights. The integrated AFM-IR response exhibits a linear dependence on molecular film height across the investigated nanometre range, supporting Beer–Lambert law at the nanoscale. We further demonstrate how this height-calibrated response can be used to estimate effective surface concentrations within individual nanoscale domains.

These findings demonstrate that AFM-IR can move beyond chemical identification toward quantitative nanoscale spectroscopy of molecular thin films. This work provides a route toward quantitative chemical analysis of functional molecular interfaces at length scales inaccessible to conventional infrared spectroscopy.

References

[1]T. G. Mayerhöfer, S. Pahlow, and J. Popp, ChemPhysChem 21, 2029–2046 (2020).

[2]E. Weyandt, F. S. Ruggeri, E. W. Meijer, and G. Vantomme, J. Polym. Sci. 62, 2208–2214 (2024).

[3]F. S. Ruggeri, B. Mannini, R. Schmid, M. Vendruscolo, and T. P. J. Knowles, Nat. Commun. 11, 2945 (2020).

[4]X. Li, S. P. Pujari, J. van der Gucht, H. Zuilhof, and F. S. Ruggeri, Nat. Commun. 16, 6761 (2025).

Noise diagnostics of memristive samples: full cycle noise measurements and AFM-based local fluctuation spectroscopy

Resistive switching systems (aka memristors) are two-terminal electronic devices whose conductance state can be tuned in an analog fashion using voltage pulses above a threshold, while at subthreshold voltages the conductance state is preserved.  In addition to the low power consumption, fast operation, and potentially sub-nanometer-scale active region of memristive devices, their analog programmability makes them particularly promising candidates for use as synaptic weights in hardware neural networks.

The inherent fluctuations in the active volume of memristive devices fundamentally determine their operation characteristics, for instance the device noise imposes severe constraints on the weight resolution in hardware neural network applications [1,2]. However, some probabilistic computing approaches require intentionally enhanced, and tunable noise levels [3,4]. Furthermore, the understanding of the noise properties also aids the understanding of the fluctuation sources and the optimizations of device fabrication [5].

Here, we present a comprehensive noise measurement methodology, which goes beyond the measurement of steady-state readout noise levels and tracks the voltage-dependent noise characteristics all along the resistive switching I(V) curves. This approach allows the detection of enhanced noise levels due to voltage-induced fluctuations, which may act as a precursor of the switching process [2]. We also discuss the implementation of this methodology as a local probe method, i.e. the possibility of noise measurement with a conductive AFM tip.

[1] Rao, M., Tang, H., Wu, J., Song, W., Zhang, M., Yin, W., ... & Yang, J. J. (2023). Thousands of conductance levels in memristors integrated on CMOS. Nature, 615(7954), 823–829.

[2] Nyáry, A., Balogh, Z., Sánta, B., Lázár, G., Jimenez Olalla, N., Leuthold, J., ... & Halbritter, A. (2025). Benchmarking stochasticity behind reproducibility: Denoising strategies in Ta₂O₅ memristors. ACS Applied Materials & Interfaces, 17(17), 25654–25662.

[3] Cai, F., Kumar, S., Van Vaerenbergh, T., Sheng, X., Liu, R., Li, C., ... & Strachan, J. P. (2020). Power-efficient combinatorial optimization using intrinsic noise in memristor Hopfield neural networks. Nature Electronics, 3(7), 409–418.

[4] Fehérvári, J. G., Balogh, Z., Török, T. N., & Halbritter, A. (2024). Noise tailoring, noise annealing, and external perturbation injection strategies in memristive Hopfield neural networks. APL Machine Learning, 2(1), 016107.

[5] Balogh, Z., Mezei, G., Pósa, L., Sánta, B., Magyarkuti, A., & Halbritter, A. (2021). 1/f noise spectroscopy and noise tailoring of nanoelectronic devices. Nano Futures, 5(4), 042002.

Seeing Phase-Change Materials Locally: Imaging Ellipsometry from Anisotropy to Reversible Optical Switching

Low-loss phase-change chalcogenides such as Sb₂S₃ and Sb₂Se₃ are emerging as key materials for reconfigurable photonics because they combine large refractive-index tunability with negligible absorption across the visible and near-infrared. Yet their performance is not determined only by the average dielectric function. At the device scale, polycrystallinity, grain orientation, and local optical anisotropy can strongly affect phase accumulation, switching thresholds, and reproducibility.

In this keynote, I will discuss how imaging spectroscopic ellipsometry, imaging Mueller matrix polarimetry, and spatially resolved optical modeling can uncover the local dielectric response of these materials beyond conventional area-averaged measurements. Using Sb₂Se₃ thin films as a first example, I will show how differently oriented crystalline domains produce strong birefringence and dichroism and yield measurable refractive-index variations at telecommunication wavelengths. I will then extend this picture to Sb₂S₃, where anisotropy and polycrystalllinity have direct consequences for reversible laser-induced phase switching, including variations in amorphization thresholds and access to partial recrystallization states.

Together, these results show that controlling crystallographic texture is as important as minimizing optical loss. Imaging ellipsometry therefore offers a powerful bridge between local structure, dielectric function, and functional performance in next-generation programmable photonic devices

Spectroscopic ellipsometry as a characterisation technique for vdW materials

One of the earliest applications of ellipsometry was to measure the thickness of thin dielectric layers on a bulk substrate, most notably silicon dioxide on silicon. Later, spectroscopic ellipsometry provided important insights into the dielectric functions of semiconductors including gallium arsenide and silicon. Research on van der Waals (vdW) materials involves the study of materials that are sometimes are only one atom or unit cell thick. Initially such samples were exclusively produced by the exfoliation of flakes from bulk crystals. Such flakes, e.g. molybdenum disulfide, can be smaller than 50 microns x 50 microns in area, making imaging spectroscopic ellipsometry a powerful method of measuring the optical properties of the flakes. In recent years researchers have been directly growing vdW materials onto substrates using semiconductor epitaxial growth techniques. In Nottingham we are growing vdW materials using molecular beam epitaxy (MBE). For example, high temperature molecular beam epitaxy (HT-MBE) has been used to grow hexagonal boron nitride (hBN) on both highly oriented pyrolytic graphite (HOPG) and sapphire substrates [1]. The HT-MBE hBN can be grown with controlled amounts of dopants e.g. carbon [2]. By measuring the optical constants of exfoliated flakes of hBN using an Accurion EP4 imaging spectroscopic ellipsometer we can compare the properties of large areas ( ~ cm2) of hBN, grown by HT-MBE on sapphire, with those of flakes exfoliated from bulk grown material. We find that the exfoliated flakes have sharper band edge transitions than HT-MBE material and that ellipsometry can be used as a fast, non-destructive, characterisation technique to assist in the optimisation of growth parameters. iSE can also measure the local optical properties of HT-MBE grown hBN in the presence of inhomogeneities introduced onto the substrate. More recently MBE has been employed to grow gallium selenide (GaSe) on sapphire [3]. A potential application for GaSe is as a deep ultra-violet (DUV) photodetector. Spectroscopic ellipsometry can provide both the dielectric functions of the grown layer, which can be compared to theoretical predictions, and the extinction coefficients of the films in the DUV, helping to inform the photodetector design.

References:

1. T.S. Cheng, et al, J. Vac. Sci. Technol. B 36 (2) 02D103 (2018).

2. N. Mendelson, et al, Nature Materials 20 (3) 321 (2021).

3. M. Shiffa, et al, Small 20 (7) 2305865 (2024).

Spectroscopic imaging ellipsometry for spatially resolved mapping of layer-by-layer oxidation in WSe2

F. Abualnaja^1,2, G. Chu¹, X. Lin¹, H.-Y. Chen³, J.-J. Lin³, H. J. Joyce¹, S. Hofmann¹, L. W. Smith³, J.A. Alexander-Webber^1,4

¹Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA, UK

²Department of Electrical Engineering, King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia

³Department of Physics, National Cheng Kung University, Tainan 701, Taiwan

⁴Department of Materials, Loughborough University, Loughborough, UK

Tungsten diselenide is a prominent candidate for nanoscale electronics and complementary metal–oxide–semiconductor technology due to its controllable p-type and n-type doping that is achievable through selective oxidation. However, characterizing the resulting oxide quality often relies on destructive or slow metrology. In this work, we demonstrate spectroscopic imaging ellipsometry (SIE) as a noninvasive technique to characterize the oxidation state of two-dimensional materials, providing spatially resolved measurements of layer thickness and uniformity [1,2,3]. We apply this method to compare few-layer WSe2 after thermal or plasma-based oxidation treatments. We show that plasma oxidation enables a highly controllable conversion of individual WSe2 layers into uniform sub-stoichiometric tungsten oxide (WOx), whereas thermal oxidation in atmospheric conditions yields a rough interface characterized by non-uniform oxide formation and blistering. Using SIE, we quantify a layer-by-layer conversion ratio, where a single WSe2 monolayer transforms into ∼1.6 nm of WOx during plasma oxidation. These findings, corroborated by atomic force microscopy, highlight the capability of SIE to resolve dielectric evolution and interface quality in layered semiconductors.

[1] Abualnaja et al. Applied Physics Letters, https://doi.org/10.1063/5.0320605 (2026)

[2] Potočnik et al. Nano Letters, Nano Letters 23, 5506 (2023)

[3] Potočnik et al. Small Methods 10, 2500437 (2025)

Figure 1: (a) Schematic crystal structure of multilayer WSe2. (b) Map of Δ across a 1-, 2-, 3-, and 4- layer oxidised WSe2 flake. Point by point fitted thickness of (c) WSe2 and (d) WO3 after oxidation.

Spatial dispersion in optical properties of square lattices of plasmonic particles revealed by Müller matrix ellipsometry

E. Bortchagovsky^a,c, F. Dai^b, M. Fleischer^b, D.R.T. Zahn^c,d

^a V.E.Lashkaryov Institute of Semiconductor Physics of NAS of Ukraine, Kyiv, 03028, Ukraine

^b Institute for Applied Physics and Center LISA+, Eberhard Karls Universität Tübingen, D 72076 Tübingen, Germany

^c Semiconductor Physics, Chemnitz University of Technology, D-09107 Chemnitz, Germany

^d Center for Materials, Architectures, and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, D-09107 Chemnitz, Germany

We demonstrate both experimentally and theoretically that spatial dispersion plays important role in the determination of optical properties of layers of plasmonic (interacting) nanoparticles. It results in the dependence of effective optical properties of such structures on the angle of incidence of the exciting light what is usually not considered in common treatment of data measured at different incidence. Additionally, we demonstrate that optical response of ordered lattices is the function of the mutual orientation of the lattice in relation to the plane of incidence despite formally such lattices are isotropic. Both effects can not be described by any standard dielectric tensor and demands the inclusion of the spatial dispersion.

Illumination of square lattice of circular symmetrical particles along any of four planes of symmetry (along rows or diagonal) produces no cross-polarization independently on the used wavelength keeping effective birefringence at inclined incidence due to elliptical shape of Fresnel zones. Such a birefringence is fixed by the plane of incidence, so effective optical constants along two orthogonal axes replace each other at the rotation of the lattice by 90°. At other non-symmetrical orientations cross-polarization arises what is well seen in measured Müller matrix. Such a behavior is shown in the Figure with color coded value of m13 element of the Müller matrix for the lattice of disc-like particles with the diameter 260 nm and the period 350 nm versus the orientation angle of the lattice in relation to the plane of incidence and the used wavelength. Spectra of ellipsometric angles measured along rows (0°) and along columns (rotated by 90°) also shown in the Figure coincide completely and demonstrate total coincidence of the resonance positions with the non-zero values of cross-polarization but gap mode when all field is concentrated between particles and their image in the substrate and no cross-talk of particles exists. It is the additional argument supporting the creation of the effective birefringence and spatial dispersion as the collective effect of interacting particles.

Color coded value of m13 element of the Müller matrix for the square lattice with the period 350 nm of gold discs with the diameter 260 nm versus the orientational angle and ellipsometric spectra measured at the orientation along the side of squares. Dotted line is the spectrum of the clean substrate.

Electrochemical variable angle spectroscopic ellipsometry of conducting polymer films at varied electrochemical doping

Duško Čakara

Centre for Micro- and Nanosciences and Technologies(NANORI)

University of Rijeka, Croatia

dcakara@uniri.hr

Conducting polymers (CP) films are the main workhorse of organic electronics, rapidly bringing new materials to the technological fields of bioelectronic devices and organic solar cells. The conductivity of CP originates from delocalized charge carriers (in most cases holes) in the phonon-coupled electronic band structure, where the concentration of mobile electrons or holes is regulated by the oxidation (or “doping”) state of these molecules [1]. The optoelectronic properties of CP films, such as their refractive index dispersion, absorption spectrum and electronic conductivity may be derived from the (complex) dielectric function, fitted from the experimental ellipsometric spectra. The presentation brings forward such an experimental assessment for two archetypal CP film (PEDOT:PSS and p(g2T-T)) electrodes in contact with an aqueous ionic solution, under varied equilibrium electrochemical potential [2]. The fitting of the ellipsometric spectra and the deconvolution of the dielectric function was achieved by applying a Drude and several Lorentz terms, enabling the decomposition of the optical absorption in terms of electrons in the bound states, from those responsible for the hole-type conductivity. A possibility for modelling such experimental data is discussed in terms of a simple Nernstian redox isotherm.

[1] Kim E.-G., Bredas J.-L., Electronic Evolution of Poly(3,4-ethylenedioxythiophene) (PEDOT): From the Isolated Chain to the Pristine and Heavily Doped Crystals (2008) Journal of the American Chemical Society, 130, 16880–16889.

[2] Pathak G., Krasińska-Krawet Z., Szyk-Warszyńska L., Čakara, D., Doping of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) films studied by means of electrochemical variable angle spectroscopic ellipsometry (2018) Thin Solid Films, 651, 31-38.

Interphases in Modern Battery Materials

LiNi 0.5 Mn 1.5 O 4 (LNMO) is a promising cathode material owing to its high operating potential of 4.75 V vs Li⁺/Li. However, the high potential triggers electrolyte oxidation. A mechanically robust cathode–electrolyte interphase (CEI) is essential for maintaining structural integrity of high-voltage lithium-ion batteries. The CEI layer functions as a protective barrier that suppresses parasitic reactions under high-voltage conditions. CEI layers are thin (< 20 nm). Therefore assessing their elastic properties is challenging. We applied the scanning force microscopy method which enablinges quantitative mechanical characterization of thin CEI layers on rough composite electrodes surfaces. The pristine crystalline LNMO surface exhibited an elastic modulus of approximately 126±20 GPa, whereas the binder/carbon (b/c) regions had a modulus of 1.9±0.1 GPa. After 200 charge discharge cycles, the elastic modulus became homogeneous with the moduli on the LNMO and b/c regions reaching≈4 GPa.

This mechanical convergence is supported by a convergence in chemical composition of the interphase between the LNMO and b/c regions. This work provides understanding of interfacial stability and establishes a robust and reproducible framework for quantifying the elastic modulus of interphase layers within composite electrodes, providing insights for the design of stable high-voltage battery systems.

Reservoir-free batteries are designed without a traditional anode material in the manufacturing process. Instead, a current collector is used. When the battery is charged for the first time, lithium deposits onto this collector effectively forming the anode in place. We investigated interface and interphase of the solid electrolyte and current collector materials with operando Kelvin Probe Force Microscopy (KPFM) [2], [3].

These examples that illustrate Scanning Force Microscopy methods are versatile and beneficial for characterizing and understanding batteries and their components.

References:

[1] X. Shi, F. Weber, H.-J. Butt1, R. Berger, Mechanical Properties of Cathode Electrolyte Interphase Layers in High-Voltage Lithium-Ion Batteries, Journal of Materials Chemistry A 2026, doi:10.1039/d5ta09458e.

[2] F. Weber, Till Fuchs, S. Kobayashi, X. Shi, L. Shen, T. Hitosugi, J. Janek, R. Berger, submitted for publication 2026.

[3] F. Weber, C. Zhu, S. Kobayashi, T. Fuchs, T. Hitosugi, J. Janek, R. Berger, Interpretation of Kelvin Probe Force Measurements in Solid-State Electrochemical Cells. ACS Applied Materials & Interfaces 17 (42), pp. 58825 - 58836 (2025).

Quantitative advanced SPM data processing with Gwyddion

To make a SPM measurement quantitative, we need to focus on different aspects:

to choose suitable calibration samples, to operate the instrument the right way and to process the data obtained from the set of measurements appropriately. With advent of novel measurement regimes that extend SPM capabilities in measurement of complex mechanical, electrical, thermal magnetic or optical properties, the complexity of all the three tasks only grows.

This talk will focus on tools that can be used within Gwyddion open source software to make at least parts of it easier. This includes methods for reducing uncertainty of measurements by proper choice of scan area and resolution with respect of the measured surface topography, by choice of reference samples and by use of methods for processing and further using the data from reference samples in different SPM modalities.

Talk will also focus on processing advanced data obtained in novel measurement regimes, like individual force-distance curves coming from off-resonance tapping regimes, high-speed image stacks or volume data representing some field distribution above the sample surface, demonstrating Gwyddion capabilities in this direction and comparing the benefits and drawbacks of storing and post-processing the complex datasets instead of their real-time analysis.

Diving into the Atom – 40 years of AFM

Franz J. Giessibl

Experimental and Applied Physics, University of Regensburg, 93053 Regensburg, Germany

franz.giessibl@ur.de

When Binnig and Rohrer provided stunning images of the atoms of the silicon 7x7 reconstructed surface with the scanning tunneling microscope (STM) [1], it came as a surprise and many initially believed they were fake. STM relies on a quantum effect, electron tunneling, with its exponential increase at a factor of ten per Å (100 pm) between two biased conductive electrodes. The strong increase of current with distance reduction is key to the high spatial resolution of STM and its monotonicity facilitates distance feedback. In 1986, Binnig, Gerber and Quate introduced atomic force microscopy (AFM) [2], a method that also images samples by probing the atomic surface arrangement of a sample with, ideally, the single front atom of a sharp tip. Richard Feynman believed that the atomic hypothesis (“…attracting each other when they are a little distance apart, but repelling upon being squeezed into one another”) contains the most scientific information in the fewest words and started chapter 1 of his Feynman Lectures on Physics [3] with this statement. The AFM uses exactly these properties of atoms to create images – it senses a surface with a sharp tip mounted on a cantilever. The challenge is that this sensor needs to be able to probe forces small enough such that neither the tips front atom nor the sample are damaged on an atomic level. The silicon 7x7 surface was first resolved by AFM in a noncontact mode [4], where the frequency shift of an oscillating cantilever was used as a feedback mechanism [5]. Further progress was enabled by the invention of the qPlus sensor, a quartz cantilever that is self sensing and oscillates at sub-Angstrom amplitudes [6]. Outfitting its tip with a CO molecule allows to image organic molecules at unprecedented resolution [7]. To our knowledge, today AFM provides the greatest spatial resolution of all microscopes by resolving structures within single atoms [8,9]. The quantum corral, introduced by Crommie, Lutz and Eigler in 1993 [10], was revisited by AFM in 2021, showing that the 102 electrons that the corral contains can be viewed as the shell of a two-dimensional atom with similar bonding properties to AFM tips as a natural atom [11]. AFM is now a powerful tool for the surface science of insulators in ultrahigh vacuum [12]. By far the most applications of AFM are in ambient conditions. Therefore, we trust that Park Systems new microscope NX1, an ambient AFM that can also use the qPlus sensor based on our Orpheus II microscope [13] will enable many new discoveries.

A qPlus sensor. B AFM image of a Fe trimer next to a Fe dimer on Cu(111). C AFM image of a single Fe atom on Cu(111)2^,6. D Quantum corral with one perturbing atom.⁷

References

1. G. Binnig et al., Phys. Rev. Lett. 50 120 (1983).

2. G. Binnig et al., Phys. Rev. Lett. 56 930 (1986).

3. R. P. Feynman et al., The Feynman Lectures on Physics, Addison Wesley 1963.

4. F. J. Giessibl, Science 267, 68 (1995).

5. T. R. Albrecht et al., J. Appl. Phys. 69, 668 (1991).

6. F. J. Giessibl, Rev. Sci. Instrum. 90, 011101 (2019).

7. L. Gross et al., Science 325 1110 (2009).

8. M. Emmrich et al., Science 348 308 (2015).

9. F. Huber et al., Science 366 235 (2019).

10. M.F. Crommie, Science 2623 218 (1993).

11. F. Stilp et al., Science 372 1196 (2021).

12. J. Hütner et al., Science 385 1241 (2024).

13. K. Pürckhauser et al., Rev. Sci. Instrum. 91, 083701 (2020).

Feeling the Lattice: AFM as a Real-Space Probe of Charge Transport in Organic Semiconductors

Organic semiconductors are prized for their mechanical flexibility, which raises a basic question: does softness limit how well they transport charge? The link turns out to be more intimate than it first appears. Macroscopic stiffness is the long-wavelength, zero-frequency limit of the acoustic phonon response, and the low-energy phonons it reflects are precisely those implicated in charge transport. Mechanics and electronics are therefore not separate properties of these materials but two readings of the same underlying structure.

Atomic force microscopy is the natural tool for probing this link directly, because it captures both molecular order and nanomechanics in real space — on the same

surface, under ambient conditions — as a real-pace counterpart to the reciprocal-space picture from X-ray scattering. I will show how higher-eigenmode imaging resolves polymer packing below one nanometre [1], while force-distance based nanomechanical mapping charts local stiffness across the same regions. Across semicrystalline polymers, nanoscale stiffness tracks structural order [2] — and, more tellingly, stiffness tracks carrier mobility. In the polymer PBTTT, nanomechanical texture evolves across amorphous, terraced, and ribbon phases. In a series based on small-molecule crystals of alkylated DNTT, side chains that expand the unit cell soften the crystal out of plane yet stiffen it in plane, in step with mobility [3].

Taken together, these results point to a common structural origin for mechanics and electronics in molecular materials and establish nanomechanical AFM as a tactile complement to scattering — reading structure in real space, where it matters most for transport.

References

[1] I. Dobryden, V. V. Korolkov, … D. Venkateshvaran, Nature Communications 13, 3076 (2022)

[2] S. Cristofaro D. Brandt, … Y. Olivier et al., Journal of Materials Chemistry C 13, 15506 (2025)

[3] K.-H. Hwang, D. Brandt, … D. Venkateshvaran, Nature Communications 17, 1621 (2026)

Phase nanoengineering in condensed matter for nanoelectronic applications

Phase nanoengineering enables the nanoscale tailoring of the physical properties of condensed matter systems using highly localized heating with focused lasers or thermal probes. Here, we summarize this approach through three examples: the control of spin waves in magnetic oxides, the patterning of magnetization textures in metallic multilayers, and the tuning of superconductivity in cuprate thin films.

In magnetic oxides such as YIG, laser-induced phase modification produces confined three-dimensional changes in the magnetic properties, enabling the engineering of the spin-wave band structure, and the realization of complex integrated magnonic circuits.

In metallic multilayers we show the grayscale tuning of the magnetic properties, leading to the creation of hidden magnetic information storage patterns and “moiré magnetic textures”.

In YBCO, a prototypic high-temperature cuprate superconductor, direct laser writing locally modifies superconducting properties, including critical temperature and current density, through thermally driven oxygen redistribution.

In all these examples nanoscale characterization tools such as scanning probe microscopy and optical methods provide direct access to the magnetic, electronic, and transport properties of the engineered phases.

The direct manipulation of the physical properties of condensed matter, beyond conventional nanofabrication, opens up unforeseen possibilities for the design of new advanced materials and functionalities in nanoelectronics.

Characterizing functional paper and paper fibers with the atomic force microscope

Robert Stark

Technische Universität Darmstadt, Institute of Materials Science, Peter-Grünberg-Str. 16, 64287 Darmstadt

Paper is one of the most widely used and sustainable materials in modern society. Produced primarily from renewable resources such as wood, it combines high recyclability with complete biodegradability. Owing to its unique fluidic, mechanical, and interfacial properties, paper is indispensable in applications including printing, packaging, and hygiene products. Beyond these conventional uses, it also offers considerable potential for advanced technologies, including lightweight materials for mobility, medical sensors, and 4D-printed soft robots ("paperbots"). Realizing these applications requires a deeper understanding of how functionalization, aging, recycling, and environmental conditions influence the mechanical properties of individual fibers, fiber joints, and small fiber networks. The atomic force microscope (AFM) is well suited to address these questions by linking fiber structure, chemistry, and mechanics at the nanoscale.

AFM provides complementary characterization methods: high-resolution imaging reveals the distribution of polymers and the effects of functionalization, while indentation experiments quantify local mechanical properties. Nanoindentation with sharp tips enables surface and near-surface characterization of cellulosic fibers at nanometer resolution, whereas colloidal probe measurements capture mechanical heterogeneities over larger length scales. These nanomechanical measurements provide key parameters for numerical models that predict the behavior of fibers and paper networks. Furthermore, AFM studies under controlled humidity offer valuable insights into moisture-dependent mechanics and the actuation mechanisms of paper-based actuators. Nevertheless, the hierarchical, heterogeneous, and highly compliant structure of cellulose fibers presents significant challenges for quantitative nanoscale characterization.