Seznam abstraktů 2024: SEKCE E - POKROČILÉ METODY PŘÍPRAVY A CHARAKTERIZACE NANOSYSTÉMŮ

Atomic force microscopes (AFM) enable characterization of surfaces at nanometer resolution, including the topography as well as electrical properties, such as surface charges, where in KPFM a feedback applies a DC-offset for measuring the local surface charges. However, this DC-bias may cause limitations for imaging in aqueous solutions as well as in electronic applications.
Recently various novel electrical AFM measurement modes have been developed that enable operation without DC-bias voltage. In AC-KPFM multiple AC-signals are applied to the AFM tip that enable compensation-based surface potential measurements in aqueous solutions. An extension towards simultaneous excitation of the AFM tip electrically as well as mechanically results in a heterodyne detection that renders the measurement independent of the lift-height, reduces influence of the cantilever cone structure, and results in a better spatial resolution and measurement accuracy. In AC-EFM an amplitude-modulated signal in the MHz-range is applied to the AFM tip that additionally enables surface potential measurements in solutions of high ionic concentration.
In a second step a new AFM system is developed for measurements at radio-frequencies (RF) up to several GHz, which converts the AFM into a RF-probing station on the sub-micrometer scale. This allows characterization of integrated circuits directly on the device during operation and is demonstrated by measurement of the voltage distribution in active RF-devices. This AFM-based system in combination with a vector-network-analyzer and a conventional probing station enables characterization of RF-circuits during operation directly on the device and wafer-level at frequencies up to 90 GHz with sub-micrometer spatial resolution.

Transition Metal Dichalcogenides have attracted immense interest due to their unique properties and potential applications in electrical and optoelectronic devices. Among these, MoS2 has drawn great attention due to its indirect to direct bandgap transition at 1.9 eV exhibiting extremely high excitonic photoluminescence in the visible range. In this work, we synthesized MoS2 on Si/SiO2 substrate using a single-step atmospheric pressure chemical vapor deposition process. We successfully obtained mono- to few-layer MoS2 films. The thickness dependence of the as-grown MoS2 layers was analyzed from the peak energy difference (Δ) between the in-plane (E2g) and out-of-plane (A1g) phonon modes in the Raman spectra (Δ value of 19 cm-1 for monolayer; 22 - 26 cm-1 for few layers; and > 26 cm-1 for bulk). Additionally, Raman analysis also allowed us to correlate the layer thickness with photoluminescence spectra. Analyses of the photoluminescence spectra reveal that the excitonic peak in MoS2 is red-shifted from mono- to few-layer MoS2 by approx. 0.04 eV. Moreover, we also observed thickness-dependent trion peak energy at room temperature. These findings provide insights into the relationship between layer thickness and quasi-particle excitations, which are useful for MoS2 based optoelectronic applications.

In actual work, the self-assembly process of low molecular weight (240 kDa) alginate (Alg) polysaccharide with cationic surfactants from the family of trimetylammonium bromide (TAB) derivatives was examined at wide polysaccharide/surfactant molar ratio range through the interpretation of the formation of non-aggregated colloidal complexes. Firstly, the critical micelle concentration (cmc) values of the investigated TAB surfactants with different chain length (C12-C18) were determined and published for the first time in phosphate buffer solution. In addition to the applied conventional measurement procedures like calorimetry, tensiometry, light scattering and equilibrium dialysis, the applicability of streaming potential technique was also demonstrated for the first time for these types of systems to gain a deeper insight into the formation process of the complexes built up by biocompatible polysaccharides and cationic surfactants. With the interpretation of the change of the streaming potential curves as a function of surfactant concentration it was clearly highlighted that both the individual and cooperative binding process of the surfactants can be clearly identified which process is followed by the aggregation of the polysaccharide-surfactant colloidal complexes and the formation of surfactant micelles in the bulk dispersion. Moreover, surfactant dependent studies revealed that the presence of the polysaccharide impacts the characteristics of the longer the chain length surfactants more than that of shorter ones.
ACKNOWLEDGEMENT: Project no TKP2021-EGA-32 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-EGA funding scheme.

Due to its accuracy and reliability in determining nm-thick overlayers on Si, XPS has been utilized as a metrology technique for many years. It has become more challenging to perform surface sensitive XPS with a soft X-ray source because the interfaces of interest are frequently hidden beneath metal electrodes or oxide layers. Higher energy X-ray probe beams have made it possible to gather photoelectron signals from further deep in the material thanks to the development of lab-based hard X-ray spectrometers (HAXPES). New options for routine application for the qualification of the procedures and components utilized in technologically significant devices are thus made available. In this talk, we will discuss the current state of the art and possible future directions for integrating hard X-ray photoelectron spectroscopy (HAXPES) and soft X-ray photoelectron spectroscopy (XPS) in the study of semiconductors and nanoelectronics. We'll discuss the benefits of employing Hard X-ray sources on a lab-based high throughput fully automated spectrometer. This includes analysis of buried interfaces, such as electronic layers below a surface capping layer, and compositional studies in the bulk of materials and interfaces below the sampling depth of soft X-rays. Reduced surface contamination's impact on the photoelectron signal is another benefit of deeper sampling. For precisely the same reason, a deeper sample depth of the Cr source enables one to explore past the potential depth of ion sputtering-induced damage. Another crucial benefit is eliminating the overlap between Auger and major photoemission peaks. This is particularly important for transistor devices based on GaN technology, for which quantification using XPS is impossible due to the overlap between Ga Auger peaks and N 1s photoelectron peaks. Thin films of various types are critical components of modern microelectronic products. Conducting films form the interconnect layers in all chips, and dielectric films provide electrical insulation. Angle-resolved or angle-dependent XPS and HAXPES(ADXPS/ADHAXPES) is a powerful, non-destructive method that provides a quantitative chemical composition depth profile for thin film structures with thicknesses within the XPS sampling depth - under 5-10 nm for an Al K alpha soft X-ray source and ~15-30nm for a Cr K alpha hard X-ray source. We will describe the use of the software StrataPHI for metrological applications in devices to estimate the structure of thin-film stacks from angle-dependent and spectral XPS and HAXPES data.

In this presentation I will highlight the different areas of research I am involved with. The areas I will introduce are the synthesis of nano-materials, nano-bio studies, nano-materials in ion insertion batteries and finally electron beam materials science. A common aspect of much of the work is to explore ways to correlate structure - property relationships, for example, the chiral dependence of single wall carbon nanotubes with respect to their electrical properties or biological cell response with respect to nanomaterial type, size and morphology.
A key feature of my research is to develop a transmission electron microscope (TEM) into an atomic-scale laboratory to fabricate, modify and characterize samples so that crucial structure property studies and synthesis studies can be conducted in high spatial resolution and high temporal resolution. Thus, the core of this presentation will look at a variety of electron beam driven chemical reactions and electron beam engineering techniques in which we can fabricate and manipulate nano-materials at the atomic level.

The presented work focuses on advanced nanoindentation techniques for measuring the mechanical properties of thin films with complex topography and structure.
Advanced nanoindentation techniques were applied to nano-composite thin films with a plasma polymer structure. These films were deposited on silicon substrates in a capacitively coupled radiofrequency discharge from a mixture of monomer hexamethyldisiloxane (HMDSO) and oxygen as the carrier gas. The power supply of the CCP and the flow rates of both HMDSO and oxygen were chosen to grow thin films under dusty plasma conditions. The deposition time was in the range of tens of minutes to achieve sufficient thicknesses (1-15 micrometers) and suppress the influence of the substrate.
To select suitable places for individual nanoindentation tests, surface topography was visualized via indentation tip scanning, and the distribution of mechanical properties was acquired via high-speed mechanical property mapping beforehand. This approach allows distinguishing between the matrix and dust particles and performing targeted measurements at specific locations.
To obtain extensive information about the mechanical properties, the studied samples underwent measurements by various indentation methods, such as nanoscale dynamic mechanical analysis (nanoDMA) with different oscillation frequencies, loading profiles, loading rates, and other parameters. Partial unloading tests were performed to obtain a depth profile of mechanical properties, with variations in the duration of individual segments, loading/unloading rates, and other indentation parameters. Additionally, creep tests were conducted to analyze the viscoelastic properties of the studied materials at various locations on the sample and using different indentation parameters such as loading/unloading profiles and the duration of the creep segment.
ACKNOWLEDGEMENTS: This research has been supported by projects LM2018097 and LM2023039 funded by the Ministry of Education, Youth and Sports of the Czech Republic and by Czech Science Foundation under project GA23-06263S.

This study presents a comprehensive characterization approach to gain deeper insights into the relationship between boron concentration, film quality, and electrochemical performance of boron-doped diamond electrodes. Advanced methodologies were employed to precisely detect and quantify boron concentration in diamond films grown as a function of Trimethylborane (TMB) in the feed gas mixture of methane and hydrogen. Surface and bulk, chemical, and electronic analytic techniques were utilized to accurately quantify boron content and its incorporation into diamond films over a wide range from 10E+15 to 10E+21 cm-3. The surface morphologies were investigated by scanning electron microscopy that has revealed a microcrystalline nature, with an inverse correlation between average grain size and increasing boron contents. Moreover, the crystallinity was confirmed by grazing incident X-ray diffraction results with the presence of (111) and (220) peaks. X-ray Photoelectron Spectroscopy, sensitive to a depth of max. 10 nm, demonstrated a linear increase in atomic percentage B (~1%) with increasing TMB. As well as linear dependence was found by Nuclear Reaction Analysis, which revealed concentrations from 10E+18 to 10E+21 cm-3 over the whole film bulk. Finally, Hall effect measurements identified electrically active carrier concentrations within the range of 10E+17 to 10E+21 cm-2.
The practical significance of controllable B concentration was demonstrated through a comprehensive study on the dependence of the electrochemical stability window (ESW), which showed a maximum ESW of 3.5 V for a boron concentration of 10E+17 cm-2 as confirmed by Hall measurements.

Despite the importance of [7]-helicene as a small chiral molecule, its interactions with zinc oxide (ZnO) nanomaterials that are prospective in photocatalysis have not yet been sufficiently explored. Here the impact of surface polarity of different ZnO facets on P/M-[7]-helicene adsorption is studied both experimentally by atomic force microscope (AFM) and theoretically by force field molecular dynamics (FFMD) and density functional tight binding simulations (DFTB). Nonpolar ZnO surfaces cause self-assembly into layered nanoislands with characteristic 4 nm layer thickness. Polar O-faced ZnO surface causes the formation of similar nanoislands, while polar Zn-faced ZnO surface is practically clean with few circular objects. Theoretical simulations show the impact of surface dipole electric field orientation and magnitude, surface chemistry and solution on helicene self-assembly. The results thus also show a way for controlling the assembly of [7]-helicene and other molecular nanomaterials for diverse applications.

Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is a scanning probe approach to optical microscopy and spectroscopy bypassing the ubiquitous diffraction limit of light to achieve a spatial resolution below 10 nanometer. s-SNOM employs the strong confinement of light at the apex of a sharp metallic AFM tip to create a nanoscale optical hot-spot. Analyzing the scattered light from the tip enables the extraction of the optical properties (absorption, reflectivity) of the sample directly below the tip and yields nanoscale images simultaneous to mechanical properties. In addition to optical nanoscopy the technology has been advanced to enable hyperspectral, nanoscale Fourier-transform spectroscopy (nano-FTIR) using broadband radiation. Equipping s-SNOM systems with IR tunable light sources, nanoscale chemical mapping can be performed at time scales of 30-300s per image. Use of material-selective frequencies in the mid-IR spectral range can be exploited to fully characterize biomaterials, polymer blends or phase change polymers with nanometer-scale domains.
New Single widely tunable laser wOPO: 1.4 - 18.4 µm (7 140 - 540 cm-1) will be discussed and broad range of applications of the s-SNOM technology for biological materials, inorganics and 2D materials research, will be presented.

In 2025 ISO and CEN international standards committees on nanotechnology will celebrate 20 years of tireless efforts in developing terminology, characterisation, safety and material specifications for all aspects of nanoparticles and nanomaterials. This talk will take us on the journey of the last 20 years with more than 100 international standard documents published and more in the pipeline. We also look at the trends in the industry, the rise and fall of wonder materials and will look ahead into future developments and global priorities and their driving forces.

It was recently proposed that agglomeration of (H2O)AgH forms the seeds of Ag0-NPs formed via Creighton’s procedure (borohydride reduction).1 Furthermore, it was shown that when Ag0-NPs are formed via Creighton’s procedure in D2O their sizes are considerably larger than that of those formed in H2O.2 We synthesized Ag0-NPs in water and heavy water, D2O, from two different precursors, silver sulfate and silver nitrate, and studied the nucleation and growth processes. The diameters of nanoparticles formed using water and D2O for Ag2SO4 and AgNO3 are 4, 9 nm, and 9, 6 nm, respectively. These measurements indicate that the solvents affect the size of the Ag0-NPs formed from sulfate and nitrate salts in opposite directions. It was proposed that the isotope effect in the reduction of Ag2SO4 is due to different hydrogen bonding of (H2O)AgH and (D2O)AgH. TEM, UV-Vis, and XPS analyses demonstrate that the nanoparticle production process varies depending on the solvent used for each precursor. In the presence of H2O as a solvent, the Ag0-NPs generated from silver sulfate are small. In the case of silver nitrate, the nitrate is reduced to ammonia during the process, which slows down the Ag0-NPs formation and, therefore, results in larger nanoparticles. Using D2O as a solvent, XPS confirmed that nitrate was only partially converted to ammonia, i.e., the kinetic isotope effect reduces the competition of the nitrate reduction process with the Ag0-NPs formation. As a result, the sizes of the formed nanoparticles decrease. This work allows a better understanding of the mechanism underlying the solvent and anion influence on nanoparticle development.
1. T. Mondal, A. Sermiagin, D. Meyerstein, T. Zidki, H. Kornweitz, Nanoscale, 12, 1657-1672, 2020.
2. A. Sermiagin, Ph.D. Thesis, Ariel University, 2021.

Molybdenum oxides form a large group of materials resulting from the ability of Mo to possess different formal oxidation states and local coordinations, which may give rise to mixed-valency oxides indispensable for energy storage, gas sensing, electrochromic or catalytic applications. Nanostructuring and doping molybdenum oxides with foreign elements or mixing with similar or dissimilar metal oxides may theoretically substantially advance the properties of the individual oxide, although such an approach typically requires exceptionally high temperatures, high vacuum, and high-budget equipment. In this work, we present an alternative approach to creating arrays of molybdenum oxide mixed with niobium oxide nanostructures via a simple, self-organized, room-temperature electrochemical anodizing of thin Al layers superimposed on thin Mo-Nb metal-alloy layers of variable component concentrations prepared by the magnetron sputter-deposition. Anodizing was carried out in sulfuric or oxalic acid solutions, resulting in the formation of porous anodic alumina (PAA), followed by PAA-assisted oxidation of the alloy underlayers, and finishing with selective dissolution of the PAA overlayers. Detailed XPS analysis of Nb 3d and Mo 3d narrow-scan spectra revealed that the highest amount of Mo in the nanostructures’ surface was 93 at.% (Mo+Nb = 100%). The dominating molybdenum-oxide component comprised Mo cations with various oxidation states (Mo6+, Mo5+, Mo4+, and Mo3+), whereas the niobium-oxide inclusion was entirely stoichiometric Nb2O5. The success of preparing and analyzing the Mo-Nb mixed-oxide nanostructures is vital for understanding the formation-structure-morphology relationship and exploring the functional properties of the novel nanoarrays. This research was supported by GACR grant no. 23-07848S.

Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT) nanofiber-based materials represent advanced solutions for application in wearable electronics due to their biocompatibility, lightweight, permeability and improved sensitivity related to their large surface area. Since PEDOT is a conductive polymer, the electrospinning process for manufacturing thin, flexible nonwovens made of homogeneous nanofibers is not well-studied yet. In this research, we have investigated the fabrication and characterization of electrospun conductive nanofibers composed of varying concentrations of PEDOT mixed with poly(ethylene oxide) (PEO). The electrospinning technique was employed to produce these conductive nonwovens, and their morphological properties were evaluated using scanning electron microscopy (SEM). To enhance the water resistance of nanofibers, a thermal treatment was applied to remove excess PEO. The resulting samples demonstrated significant improvements in water stability, whereas untreated samples dissolved in pure water almost immediately. Electrical characterization of conductive nonwovens was performed, revealing resistivity in several hundreds of Ohm•m. To further investigate the electrical response and electrochemical behavior of the material when in contact with specific compounds, we conducted electric impedance spectroscopy (EIS) and cyclic voltammetry (CV). The EIS measurements provided insights into the impedance characteristics, while the CV analysis elucidated the redox properties and a purely resistive behavior. Our findings suggest that the optimized PEDOT/PEO nanofibers exhibit promising electrical and electrochemical properties, making them suitable for applications in flexible electronics and wearable sensors. This study contributes to the understanding of the relationship between the fabrication process, structural morphology, and functional performance of electrospun conductive nonwovens with the potential to significantly impact the wearable technology field.