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Organic semiconductors (OSC) are attracting much interest for (opto)electronic applications, such as photovoltaics, LEDs, sensors or solid state lasers. In particular, crystals formed by small π-conjugated molecules have shown to be suitable for constructing OSC devices. However, the (opto)electronic properties are complex since they depend strongly on both the mutual orientation of molecules as well as the perfection of bulk crystal surfaces. Hence, there is an urgent need to control nano-topographic OSC features in real space. Here we show that friction force microscopy in water is a very suitable technique to image the free surface morphology of an OSC single crystal (TDDCS) with sub-nanometer resolution. We demonstrate the power of the method by direct correlation to the structural information extracted from combined single crystal (SC-) and specular (s-) XRD studies, which allows us to identify the pinning centers encountered in the stick-slip motion of the probing tip with the topmost methyl groups on the TDDCS surface.
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http://dx.doi.org/10.1088/0953-8984/28/13/134002 | DOI Listing |
Structure
September 2025
Institute of Anatomy, University of Bern, 3012 Bern, Switzerland. Electronic address:
Cryo-electron tomography (cryoET) provides 3D datasets of organelles and proteins at nanometer and sub-nanometer resolution. However, locating target proteins in live cells remains a significant challenge. Conventional labeling methods, such as fluorescent protein tagging and immunogold labeling, are unsuitable for small structures in vitrified samples at molecular resolution.
View Article and Find Full Text PDFMicroscopy (Oxf)
August 2025
International Center for Quantum Materials, and Electron Microscopy Laboratory, School of Physics, Peking University, Beijing, China.
Scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) has emerged as a state-of-the-art characterization modality in materials science, undergoing transformative advancements over the past decade. Revolutionary developments in monochromator technology have pushed EELS energy resolution into the sub-10 meV regime, enabling investigations of low-energy excitations such as phonons, excitons, plasmons, and polaritons at nanometer and sub-nanometer scales, in addition to traditional core-loss spectroscopy. Besides to the high spatial resolution and high energy resolution, the coherent nature of STEM electron probes now allows momentum-resolved spectral information to be acquired, providing an ideal platform for correlating nanoscale structural features with functional properties at the nanometer and atomic level.
View Article and Find Full Text PDFMicrosc Microanal
July 2025
Department of Materials Science and Engineering, Hearst Memorial Mining Building, University of California, Berkeley, CA 94720, USA.
Irradiation produces a distribution of defect sizes in materials, with the smallest defects often below one nanometer in size and approaching the scale of a single unit cell in metals. While high-resolution scanning transmission electron microscopy (STEM)-based imaging can directly image structures at this level, techniques such as four-dimensional STEM (4D-STEM) enable characterization of materials across large fields of view, capturing a more representative volume that can be valuable for quantifying defects, their distributions, and the associated strain fields. Here we present a combined HRSTEM and 4D-STEM approach to study the model system of He bubble implantation in an Au thin film.
View Article and Find Full Text PDFAs optical systems evolve toward larger apertures, higher precision, and broader frequency bands, sub-nanometer accuracy and sub-millimeter resolution residual birefringence metrology play a crucial role in the preparation and manufacturing of large-aperture optical materials. Traditionally, polarization errors in optical elements are evaluated using specialized instruments based on the photoelastic effect. However, these high-precision instruments are expensive, have slow testing speeds, and restrict the resolution and aperture size.
View Article and Find Full Text PDFHolographic vibrometry is a family of interferometric methods for contactless, full-field vibration measurements. Harmonic surface vibrations with high frequencies (hertz to upper megahertz regime) and low displacements (sub-nanometer to micrometer) as found in micro-electromechanical systems can be characterized. Using frequency shifting, it is possible to obtain static interference or low-frequency beats between the reference arm and one of the sidebands generated by the vibration in the object arm.
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