Ilya A. Zavidovskiy

Two-dimensional MoS2 is a promising channel material for beyond-silicon memory devices, but its chemically inert van der Waals surface makes the direct atomic layer deposition (ALD) of continuous high-k and ferroelectric gate stacks highly challenging in technologically relevant top-gate architectures. Here, we demonstrate an ultrathin sputtered HfOx seed layer as a scalable surface-functionalization strategy enabling the conventional H2O-based ALD of ferroelectric Hf0.5Zr0.5O2 (HZO) on near-monolayer metalorganic chemical vapor deposition-grown MoS2. The HfOx seed layer strongly improves HZO uniformity, while Raman spectroscopy and x-ray photoelectron spectroscopy indicate no significant structural degradation and only limited oxidation of the ultrathin MoS2 channel. Using this seed-assisted integration scheme, we realize top-gate MoS2 ferroelectric field-effect transistors with low gate leakage currents, efficient channel modulation, and nonvolatile memory operation. These results establish sputtered HfOx seed-layer functionalization as an effective route for the scalable integration of ferroelectric HZO with two-dimensional MoS2 channels in top-gate memory devices.

Selecting photothermal nanofluids requires balancing solar absorption against nanoparticle demand and material cost. We compare Ag, Au, Cu, MoS₂, WS₂, TaS₂, TiN, and Ti₃C₂ using a common Mie-theory framework for homogeneous spherical particles in water. Calculations over 300–2500 nm and particle radii of 2–200 nm relate spectral absorption and scattering to nanoparticle loading. Solar-weighted absorptance is combined with a minimum-loading criterion for prescribed absorption targets and a cost-normalized absorbed power metric. Under the adopted optical and price assumptions, MoS₂, WS₂, TiN, and Ti₃C₂ show favorable cost-normalized responses, whereas the assigned price penalizes TaS₂, illustrating why high optical absorption alone does not determine material selection. The absorption metric represents the combined water–particle system and should not be interpreted as evaporation or device efficiency. Its cost normalization includes only screening-level nanoparticle material cost and does not account for synthesis, purification, size selection, surface modification, colloidal stabilization, equipment, lifetime replacement, or water production costs. It also does not isolate nanoparticle-induced heating from absorption by water. The framework therefore provides a material-level screening tool for direct solar absorbers relevant to steam generation, rather than a prediction of device performance or industrial desalination cost.

Vanadium oxides are known for a large diversity of crystalline phases with different interesting physical and chemical properties and a wide range of applications. However, due to the close stoichiometric composition of these phases, the growth parameters should be carefully adjusted for each VOx phase. In this work, we propose a method of vanadium oxide thin films phase engineering: growth of amorphous VOx in an oxygen atmosphere at room temperature, followed by vacuum annealing. Our method enables target synthesis of VO2, V4O9, V3O7, and V2O5 phases. A desired phase in a polycrystalline thin-film form can be obtained by finely tuning oxygen pressure during room temperature deposition while keeping other parameters constant. The synthesized thin films can be utilized for various applications: neuromorphic hardware, supercapacitors, sensors, and catalysis.

The development of nanophotonics is hindered by a fundamental trade‐off between a material's refractive index ( n ) and its electronic bandgap ( E _g ), which severely restricts the choice of materials for short‐wavelength applications. This challenge is particularly acute in the visible and ultraviolet (UV) spectra, where high‐performance devices require materials that are simultaneously highly refractive and transparent. Here, we report on the van der Waals (vdW) crystal cadmium phosphorus trisulfide (CdPS ₃ ) as a solution to this long‐standing problem. Through comprehensive optical and structural characterization, we show that CdPS ₃ possesses an anomalously high in‐plane refractive index across the visible spectrum approaching three in the near‐UV, combined with a wide indirect bandgap. This combination of properties is validated by first‐principles calculations and direct near‐field imaging of highly confined waveguide modes. These findings establish CdPS ₃ as a leading material for UV–visible photonics, opening a new pathway for the development of high‐density integrated circuits and metasurfaces.

Molybdenum blue dispersions were synthesized via an ion-exchange approach using hydroquinone and glucose as reducing agents to clarify the influence of reductant chemistry on redox evolution and colloidal stability. Electrolyte-free conditions enabled controlled self-assembly of reduced polyoxomolybdate clusters. UV–Vis spectroscopy revealed characteristic absorption bands at ~750 and ~1100 nm associated with intervalence charge transfer in mixed-valence Mo⁵⁺/Mo⁶⁺ clusters, with hydroquinone stabilizing more deeply reduced clusters, while glucose-derived systems demonstrated a higher degree of reduction with a higher ratio of reducing agent to metal. Time dependence of oxidation–reduction potential and optical density measurements demonstrated prolonged redox equilibration and gradual self-organization over several weeks. Dynamic light scattering confirmed the formation of nanoclusters with comparable hydrodynamic diameters of approximately 3.5 nm for both reducing agents. Raman and FT-IR spectroscopy indicated structurally similar polyoxomolybdate frameworks. In contrast, electrokinetic measurements revealed pronounced differences in surface chemistry and stability: hydroquinone-derived dispersions exhibited robust, pH-independent electrostatic stabilization, whereas glucose-derived systems showed weaker, pH-dependent stabilization and rapid electrolyte-induced aggregation. These results demonstrate that the nature of the reducing agent has an impact on the synthesis and colloidal behavior of molybdenum blue dispersions synthesized by the ion-exchange route.