V.E. Lashkaryov Institute of Semiconductor Physics

Abstract The emergence of artificial intelligence and neuromorphic computing has revealed the importance of two-dimensional (2D) layered materials in the field of non-volatile memory technologies. Based on the available literature, this is the very first report demonstrating the integration of 2D Transition Metal Carbide MXenes, i.e. Titanium Carbide (Ti 3 C 2 T x ) and Vanadium Carbide (V 2 CT x ) with MoS 2 from the Transition Metal Dichalcogenide family for memristor devices. The nanoscale Ti 3 C 2 T x and V 2 CT x MXene were employed as the bottom electrodes (as independent as well as bi-electrode combination) deposited uniformly on the substrate, along with the successful transfer of Chemical Vapor Deposition grown few-layers MoS 2 onto the nano-ranged sheets of MXene with Ag utilized as the top electrode. Raman analysis and Optical microscopy images indicated the fabrication of the novel best-yielding device Ti 3 C 2 /V 2 C/MoS 2 /Ag structure with high fidelity. Additionally, current-voltage (I-V) analysis showcased bipolar resistive switching phenomena comprising of an efficiently low SET voltage of 0.6 V, endurance of up-to 3000 cycles and retention of over 10 3 seconds, extrapolated over million seconds. The stability of SET/RESET voltages, cycle-to-cycle and device-to-device reproducibility is demonstrated by 18 devices for a memristor array of (5 ×5), emphasizing the unexplored potential of MXene and MoS 2 based memristors for the scalable and large-area integration of devices in future memristors. Furthermore, Ti 3 C 2 /V 2 C/MoS 2 /Ag memristor also exhibited synaptic features of potentiation and depression showcasing potential to be employed in neuromorphic computing techniques.

Films of nanosized titanium dioxide doped with 0.1–10 mol. % of tungsten ions (hereinafter referred to in the text as W/TiO2) using titanium tetraisopropoxide Ti(OiPr)4 and (NH4)10W12O41·nH2O were obtained by the sol-gel method using non-ionic amphiphilic triblock copolymer Pluronic (P123) as a templating agent. The samples were investigated by XRD, Raman, UV-Vis and FTIR spectroscopy. W/TiO2 dispersions with the same chemical composition have been prepared via gelation of the solution of films precursors, after their drying at room temperature and calcination at 500 °C. Crystalline anatase phase was registered in XRD and Raman spectra of W/TiO2 films up to 10 % tungsten content with a minimum disturbance of the anatase-type structure. XRD patterns of W/TiO2 powders showed anatase (20–25 nm) and rutile (35–40 nm) nanocrystalline phases. The formation of tungsten oxide phases was fixed at its 10 % content. The photocatalytic activity of the films was examined in the photoreduction reaction of Cr(VI) ions to Cr3+ under UV irradiation in the presence of Na2EDTA as an electron donor. Films doped with 5–7 mol. % tungsten ions have higher photocatalytic activity compared to non-doped ones and demonstrated stable activity during 8–10 cycles. The addition of tungsten ions to titania matrix significantly improved its photocatalytic behavior. Tungsten ions doping promotes efficiency of the charge pair separation by trapping of photogenerated electrons with W5+ formation and preventing the charge recombination. When the dopant concentration was increased to 10 %, the photocatalytic efficiency a little decreased. To increase the photocatalytic activity of the coatings, the bare TiO2 and W/TiO2 samples were irradiated in a plasma mixture of hydrogen and argon (1 : 1). The efficiency of undoped TiO2 films has been increased 16 times, and W/TiO2 only by 2 times as the results of tungsten ions affecting the recombination processes.

The blue shift of surface plasmon resonance (SPR) peak of ZnO/Ag nanocomposites due to magnetic field pre-treatment was detected. Observed features were attributed to the ZnO refractive index changes due to magnetization. with MiePlot 4.16 Software were carried out to obtain information about principal possibility of localized surface plasmon resonance (LSPR) peak position changing due to changing of ZnO nanoparticles refractive index due to magnetization in external magnetic field. Obtained results are in good agreement with experiment. Possible applications of detected phenomenon were presented.

Purely electrical control of the Dzyaloshinskii-Moriya interaction (DMI) without any external magnetic field is explored in a magnetic Weyl semimetal (WSM). The underlying mechanism for the DMI in the WSM is the recently identified asymmetrical indirect spin-spin interaction compatible with the inversion symmetry of the structure. While the necessary imbalance in the fermion population of opposite chirality is normally achieved with non-orthogonal external electric and magnetic fields (i.e. the axial anomaly), it is found that the intrinsic axial magnetic field characteristic to an inhomogeneous magnetic texture can play the role of the magnetic field. When applied to the magnetic domain walls as specific examples, our theoretical analysis clearly illustrates that the resulting DMI is pinned by and can in turn significantly affect the wall textures. As the appearance and strength of the DMI can be solely controlled by the applied electric field, this mechanism enables electrical modulation of magnetic domains including their excitation in the WSMs. Numerical calculations highlight significant advantages of the WSM over the conventional magnetic materials in spintronic applications such as the racetrack memory.

Abstract Asymmetric sulfur‐terminated compounds (STC) and allyl‐terminated compound 2‐(4‐butoxyphenyl)‐1,3‐dimethylcyclo‐hepta[c]pyrrole‐6(2H)‐thione (ATC) dyes are deposited by evaporation in vacuum (PVD) on glass and gold (Au) substrates. Au is deposited by PVD on a rotating glass disk as a thin layer of nanoparticles (NPs), which exhibited a plasmon band at 600 nm. The influence of the dye chemical structure and the substrate with and without gold NPs on the optical properties of the system is studied using in situ optical spectroscopy. A significant difference in the evolution of transmission spectra and morphology of the same dye deposit; however, deposited on glass and Au surfaces is investigated. At the beginning of condensation, molecules of several dyes on the Au surface cause a redshift of the plasmon band. Increasing the number of condensed molecules results in new weak absorption bands in the near infrared region and a redshift of the strong absorption bands corresponding to the absorption of dyes molecules.