arXiv subjects

Maxim Sokol

Publications and source records attributed to Maxim Sokol.

6 recordsLinked to original sources

arXiv2026

Near-Atomic-Scale Compositional Complexity in a 2D Transition Metal Oxide

2D materials hold transformative promise for next-generation nanoelectronics. However, successfully integrating these materials from laboratory-scale discoveries into real-world devices depends on precisely controlling their properties, which are fundamentally determined by their composition. Detailed characterisation using atom probe tomography of 2D Ti0.87O2, a candidate high-$\kappa$ dielectric, reveals deviations from its commonly assumed stoichiometry. Compositional analysis and comparison with the bulk K0.8[Ti1.73Li0.27]O4 precursor evidences an oxygen deficit indicative of oxygen vacancy formation in the 2D material, as well as the retention of low concentrations of alkali metals that were presumed to be removed during synthesis. Such deviations from stoichiometry indicate a reconstruction mechanism that mitigates the effect of the characteristic, negatively charged vacancies on the titanium sublattice, thereby influencing the local electronic structure and, consequently, functional properties. These findings underscore the importance of a detailed compositional analysis in both understanding and optimizing the extraordinary functional properties of 2D materials, opening pathways to tailored functionalities in next-generation nanoelectronics.

cond-mat.mtrl-sci↗

arXiv2025

Self-supported bulk MXene electrodes for electrochemical hydrogen applications

MXenes are promising candidates for electrochemical applications due to their high conductivity, tunable surface chemistry, and catalytic potential. However, their use in bulk electrode form remains unexplored despite advantages such as higher current density and improved mechanical integrity. Herein, we present a methodology for the fabrication of self-supported vdW solid Ti3C2Tz MXene electrodes, produced by cold compaction followed by vacuum heat treatment at 600 {\deg}C, which effectively removes interlayer confined water and stabilizes the bulk 3D structure. The resulting binder-free electrodes exhibit enhanced mechanical robustness along with structural and chemical stability in various electrolytes. The MXene electrodes demonstrate adequate HER activity while maintaining electrochemical stability over time, with minimal oxidation or changes in termination surface chemistry. This approach is scalable and cost-effective, overcoming limitations of nanoscale MXene architectures in electrochemical environments and offering a practical pathway toward MXene-based materials for sustainable hydrogen energy technologies.

cond-mat.mtrl-sci↗

arXiv2023

Facilitating Atom Probe Tomography of 2D MXene Films by In Situ Sputtering

2D materials are emerging as promising nanomaterials for applications in energy storage and catalysis. In the wet chemical synthesis of MXenes, these 2D transition metal carbides and nitrides are terminated with a variety of functional groups, and cations such as Li+ are often used to intercalate into the structure to obtain exfoliated nanosheets. Given the various elements involved in their synthesis, it is crucial to determine the detailed chemical composition of the final product, in order to better assess and understand the relationships between composition and properties of these materials. To facilitate atom probe tomography analysis of these materials, a revised specimen preparation method is presented in this study. A colloidal Ti3C2Tz MXene solution was processed into an additive-free free-standing film and specimens were prepared using a dual beam scanning electron microscope / focused ion beam. To mechanically stabilize the fragile specimens, they were coated using an in situ sputtering technique. As various 2D material inks can be processed into such free-standing films, the presented approach is pivotal for enabling atom probe analysis of other 2D materials.

cond-mat.mtrl-sci↗

arXiv2023

Near-Atomic Scale Perspective on the Oxidation of Ti$_3$C$_2$T$_x$ MXenes: Insights from Atom Probe Tomography

MXenes are a family of 2D transition metal carbides and nitrides with remarkable properties and great potential for energy storage and catalysis applications. However, their oxidation behavior is not yet fully understood, and there are still open questions regarding the spatial distribution and precise quantification of surface terminations, intercalated ions, and possible uncontrolled impurities incorporated during synthesis and processing. Here, atom probe tomography analysis of as-synthesized Ti$_3$C$_2$T$_x$ MXenes reveals the presence of alkali (Li, Na) and halogen (Cl, F) elements as well as unetched Al. Following oxidation of the colloidal solution of MXenes, it is observed that the alkalies enriched in TiO$_2$ nanowires. Although these elements are tolerated through the incorporation by wet chemical synthesis, they are often overlooked when the activity of these materials is considered, particularly during catalytic testing. This work demonstrates how the capability of atom probe tomography to image these elements in 3D at the near-atomic scale can help to better understand the activity and degradation of MXenes, in order to guide their synthesis for superior functional properties.

cond-mat.mtrl-sci↗

arXiv2021

Ti$_3$C$_2$T$_x$ MXene Enabled All-Optical Nonlinear Activation Function for On-Chip Photonic Deep Neural Networks

Neural networks are one of the first major milestones in developing artificial intelligence systems. The utilisation of integrated photonics in neural networks offers a promising alternative approach to microelectronic and hybrid optical-electronic implementations due to improvements in computational speed and low energy consumption in machine-learning tasks. However, at present, most of the neural network hardware systems are still electronic-based due to a lack of optical realisation of the nonlinear activation function. Here, we experimentally demonstrate two novel approaches for implementing an all-optical neural nonlinear activation function based on utilising unique light-matter interactions in 2D Ti$_3$C$_2$T$_x$ (MXene) in the infrared (IR) range in two configurations: 1) a saturable absorber made of MXene thin film, and 2) a silicon waveguide with MXene flakes overlayer. These configurations may serve as nonlinear units in photonic neural networks, while their nonlinear transfer function can be flexibly designed to optimise the performance of different neuromorphic tasks, depending on the operating wavelength. The proposed configurations are reconfigurable and can therefore be adjusted for various applications without the need to modify the physical structure. We confirm the capability and feasibility of the obtained results in machine-learning applications via an Modified National Institute of Standards and Technology (MNIST) handwritten digit classifications task, with near 99% accuracy. Our developed concept for an all-optical neuron is expected to constitute a major step towards the realization of all-optically implemented deep neural networks.

physics.optics↗

arXiv2019

Bonding and oxidation protection of Ti${_2}$AlC and Cr${_2}$AlC for a Ni-based Superalloy

Alumina forming, oxidation and thermal shock resistant MAX phases are of a high interest for high temperature applications. Herein we report, on bonding and resulting interactions between a Ni-based superalloy, NSA, and two alumina forming MAX phases. The diffusion couples Cr${_2}$AlC/Inconel-718/Ti${_2}$AlC were assembled and heated to 1000 or 1100°C in a vacuum hot press under loads corresponding to stresses of either 2 MPa or 20 MPa. The resulting interfaces were examined using X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Good bonding between Cr${_2}$AlC and NSA was achieved after hot pressing at 1000°C and a contact pressure of only 2 MPa; in the case of Ti${_2}$AlC a higher temperature (1100°C) and pressure (20 MPa) were needed. In both cases, a diffusion bond was realized with no evidence of interfacial damage or cracking after cooling to room temperature. Twenty thermal cycles from room temperature to 1000°C showed that Ti${_2}$AlC is a poor oxidation barrier for Inconel-718. However, in the case of Cr${_2}$AlC no cracks, delamination nor surface degradation were observed, suggesting that this material could be used to protect Inconel-718 from oxidation.

cond-mat.mtrl-sci↗