arXiv subjects

Alexei Tolstik

Publications and source records attributed to Alexei Tolstik.

3 recordsLinked to original sources

arXiv2026

Composition-Driven Tunable Optical and Electrical Properties in Van der Waals Ferroelectric NbOI2-xClx Alloys

Layered niobium oxide dihalides NbOX2 (X = I, Cl), as a new family of Van der Waals (vdW) ferroelectrics, have attracted extensive attention, while achieving non-volatile modulation of their optical and electrical properties remains challenging, thereby limiting their integration into next-generation nanoelectronics and optoelectronics. Here, we report the controlled fabrication of highly crystalline NbOI2-xClx vdW alloys with composition-driven tunable optical and electrical properties via a chemical vapor transport method. Comprehensive experimental characterization combined with first-principles calculation shows that the crystal lattices, phonon modes, and band structures of NbOI2-xClx can be well tailored, which are distributed between NbOI2 and NbOCl2. Both the amplitude and polarization of second harmonic generation optical signal in NbOI2-xClx exhibit pronounced compositional dependence, offering optical evidence for tunable in-plane ferroelectric characteristic. Moreover, field-effect transistors based on NbOI2-xClx display robust n-type semiconducting behavior, with threshold voltage and carrier mobility precisely modulated through adjustment of I/Cl molar ratio. Furthermore, 2D NbOI2-xClx photodetectors across all compositions exhibit exceptional gate-tunable current on/off ratio and strong polarization-sensitive photo-response. This study thus provides a new vdW ferroelectric material platform with tunable optical and electrical properties, paving the path for its implementation in modern nanophotonics and nanoelectronics.

cond-mat.mtrl-sci↗

arXiv2025

Phase Topology Stability of an Optical Vortex via an Electrically Controlled Twist-Planar Oriented Liquid Crystal Fresnel Lens

Optical vortices (OVs) have emerged as a revolutionary concept in modern photonics, offering a unique method of manipulating light beyond conventional Gaussian beams. Despite their vast potential, phase topology stability remains unaddressed, limiting their widespread adoption and performance in real-world environments. Here, we reveal the missing link to assessing the stability of optical vortices using an electrically tunable twist-planar liquid crystal (LC) Fresnel lens. The proposed LC-based lens leverages the birefringence and voltage-controlled reconfigurability of liquid crystals to dynamically probe the phase topology of singular beams. By modulating the LC orientation with an applied voltage, we restructure the optical phase in real-time without requiring modifications to the optical setup. The 3V and 35V voltage supply allows for the switch between the "topological charge detection" and "optical singular beam propagation" modes. This eliminates the need for additional optical elements, significantly simplifying the detection and characterization of vortex beams. Experimental and theoretical investigations demonstrate that the vortex topology can be unambiguously identified from the intensity profile observed in the Fourier plane of a lens. Furthermore, the designed device features low power consumption, compact form factor, and seamless integration potential, making it a promising candidate for scalable vortex-based photonic systems.

physics.optics↗

arXiv2025

Observation of Intrinsic and LED Light-Enhanced Memristor Performance in In-Plane Ferroelectric NbOI2

Two-dimensional (2D) layered ferroelectrics, as an emerging area of research, have attracted extensive attention, while memristors based on new 2D ferroelectric materials have yet to be fully explored, thereby limiting their applications in modern nanoelectronics. In this work, we report the observation of intrinsic memristive behavior in a newly discovered 2D in-plane ferroelectric material, NbOI2, and the giant enhancement of the memristive performance using LED visible light. The results show that NbOI2 exhibits intrinsically strong memristive response with a current on/off ratio of up to 10^4 and stable switching cycles, which is independent of back-gate voltage. Under LED visible light illumination, the current on/off ratio in NbOI2 is over one order of magnitude higher than that without light, meanwhile, the coercive field is significantly reduced to less than 1.22 kVcm-1, much lower than other 2D ferroelectric material-based memristors. Interestingly, both the intrinsic and the light-enhanced resistive switching phenomena only occur along the in-plane b-axis direction, indicating that the memristive behavior in NbOI2 is driven by electric field-induced and optical field-enhanced ferroelectric polarization switching mechanisms, as evidenced by a combined orientation-dependent electrical/optoelectrical measurement and sweep cycle-induced structural evolution analysis. Our study not only provides a materials strategy based on new 2D ferroelectrics for designing memristor applications, but also offers a simple optical method to enhance its performance, paving the path for its implementation in novel nanoelectronics and optoelectronics.

cond-mat.mtrl-sci↗