Crystal Layer Research Articles

Layered heterogeneous structures integrated device for multiplication, division arithmetic unit and multiple-physical sensing

A layered heterogeneous structure (LHS), consisting of silver, liquid crystal, and nonlinear dielectric layers, is proposed to realize functions of computing and sensing. By leveraging the optical Tamm state, the intrinsic absorption principle of liquid crystal, and nonlinear effects, the design of an integrated device capable of passive multiplication and division operations, along with high-performance multi-physical quantity sensing functionalities, is achieved. The given LHS exhibits Janus properties, with different physical functions manifested depending on the direction of electromagnetic wave (EW) propagation. During forward propagation of EWs, the LHS displays high and sharp absorptivity peaks at 774.8 and 1517.6 nm. The relationship between the two peaks approximates a frequency multiplication factor of 1.960, enabling signal multiplication. Furthermore, the two absorptivity peaks at different wavelengths facilitate the sensing of serum creatinine solution concentration and external pressure, with sensitivity (S), quality factors (Q), and figure of merit (FOM) of 266.76 μmol L−1/nm and 213.33 GPa/nm, as well as 248.76 and 348.22, 84.1 L (μmol)−1 and 49.06 GPa−1, respectively. During backward propagation of EWs, absorptivity peaks with distinct resolutions are observed at 1423 and 2809 nm, with a multiple relationship between them of 1.974, enabling frequency doubling for signal division. Additionally, the absorptivity curve facilitates temperature sensing over a wide range from 257 to 347 K. Owing to the unique temperature S of liquid crystal, different sensitivities and resolutions are observed at 257 to 297 K and 307 to 347 K, with S of 1.015 and 0.686 K/nm, and corresponding Q and FOM of 21.57 and 12.576, 0.076 K−1 and 0.003 04 K−1, respectively.

Liquid-Phase Exfoliation of 3D Metal-Organic Frameworks into Nanosheets.

Traditionally, the acquisition of 2D materials involved the exfoliation of layered crystals. However, the anisotropic bonding arrangements within 3D crystals indicate they are mechanically reminiscent of 2D counterparts and could also be exfoliated into nanosheets. This report delineates the preparation of 2D nanosheets from six representative 3D metal-organic frameworks (MOFs) through liquid-phase exfoliation. Notably, the cleavage planes of exfoliated nanosheets align perpendicular to the direction of the minimum elastic modulus (Emin) within the pristine 3D frameworks. The findings suggest that the in-plane and out-of-plane bonding forces of the exfoliated nanosheets can be correlated with the maximum elastic modulus (Emax) and Emin of the 3D frameworks, respectively. Emax influences the ease of cleaving adjacent layers, while Emin governs the ability to resist cracking of layers. Hence, a combination of large Emax and small Emin indicates an efficient exfoliation process, and vice versa. The ratio of Emax/Emin, denoted as Amax/min, is adopted as a universal index to quantify the ease of mechanical exfoliation for 3D MOFs. This ratio, readily accessible through mechanical experiments and computation, serves as a valuable metric for selecting appropriate exfoliation methods to produce surfactant-free 2D nanosheets from various 3D materials.

Preparation of polymer dispersed liquid crystal doped with bilayer nanofiber membranes and phase‐change microcapsule coating for enhanced infrared modulation

AbstractThe effective manipulation and regulation of infrared (IR) radiation represent significant advancements in the realm of liquid crystal applications. In this investigation, the synergistic integration of nanofiber membranes and phase change microencapsulated film with polymer dispersed liquid crystal (PDLC) layers was employed for IR modulation. To obtain the excellent electro‐optical properties of PDLC composite films, the ratio of the PDLC system, the thickness of the nanofiber membrane, and the concentration of phase‐change microcapsules were meticulously regulated, and the polymer network morphology of the PDLC films was analyzed to achieve a high contrast ratio (162.72) of PDLC composite films. The fabricated PDLC composite devices show excellent IR shielding efficiency of 15% in the presence of doped nanofiber membranes and phase change microencapsulated films. Notably, patterned nanofiber layers and phase‐change microcapsule coating were obtained by template electrospinning, resulting in patternable PDLC composite film devices.

Molecular dynamics study on phase change properties and their nano-mechanism of sugar alcohols: Melting and latent heat

Sugar alcohol phase change materials have gained considerable attention for heat storage in recent years owing to their higher thermal conductivity and larger latent heat compared to traditional paraffin materials. However, knowledge about the reason of large latent heat and latent heat difference among diverse sugar alcohols as well as the mechanism of melting process remains elusive. In this study, molecular dynamics simulation was employed to investigate the melting process and latent heat of four sugar alcohols (glycerol, erythritol, arabinitol, and mannitol). Melting points and latent heat of fusion were determined first, different melting temperatures were observed under different one-dimensional heat conduction directions in several sugar alcohols. It was found that the strength of intermolecular interactions within molecular crystal layers has a positive correlation with the anisotropic melting tendencies, which can be more intuitively reflected by the difference in the number of hydrogen bonds within the molecular layers. In addition, the decomposition of the latent heat of fusion revealed that the latent heat is mainly composed of van der Waals and Coulombic contributions, where the interaction between hydroxyl groups accounts for a major part. Hydrogen bond analysis demonstrated that the latent heat of fusion is partly due to the breakage of hydrogen bonds during the phase transition of melting. It was also noted that the differences in the hydrogen bonding lifetimes between different sugar alcohols may be related to the magnitude of latent heat of fusion. Erythritol and mannitol which coincidentally happened to have an even number of carbon atoms can fulfill the properties of better PCMs compared to glycerol and arabinitol, which have an odd number of carbons. Those results will pave the way for better design optimization and performance evaluation of sugar alcohols as phase change materials.

Adipic acid-mediated hydrogen bonding network allocation for efficient proton conduction in water-stabilized lamellar MOF membranes

The poor water-stability and cross-layer proton transfer property pose a challenge to the lamellar metal–organic frameworks (MOFs) membrane when acting as a promising proton exchange membrane. Herein, we report an adipic acid-mediated strategy to improve the water-stability and the cross-layer proton conductivity of CuTCPP lamellar MOF membrane, which achieves a maximum power density and current density of 112.6 mW cm−2 and 424.4 mA cm−2, respectively. Adipic acid with extra functional groups (–PO3H2, –COOH) stably bridges the adjacent crystal layers via the terminal carboxylic acid anchoring Cu sites. In particular, the extra functional groups introduced into the adipic acid regulate the allocation of hydrogen bonding networks in an umbrella-shape around adipic acid with copper-porphyrin structures as external margin, enriching the coherence of hydrogen bonding network on the proton transport path. Benefiting from the regular pore structure of MOF, the optimized hydrogen bonding networks in adjacent crystal layers construct a more abundant through-plane transfer pathway. The resultant through-plane proton conductivities of CuTCPP-PO3H2/–COOH membranes are up to 108/89 mS cm−1 at 80 °C and 100 % RH, which is ∼ 6-fold higher than that of the pristine CuTCPP membrane (13 mS cm−1), with a conductivity attenuation of < 5 % during a humidity cycling test for 12 times.

Extending the operational limit of a cooled spatial light modulator exposed to 200 W average power for holographic picosecond laser materials processing

The phase range of a Spatial Light Modulator (SLM) requires full 2π response for accurate phase modulation of the incident laser wavefront to create the desired structured intensity distribution. While cooled SLM’s allow increased power exposures, degradation in performance occurs with average powers P>100 W in a Gaussian beam due to residual absorption and consequent heating of the liquid crystal (LC) layer which seriously limits the phase stroke and diffraction efficiency. By introducing a refractive flat top intensity generator ahead of a cooled SLM, we have extended the phase range to Δφ = 2π at incident power P=210 W with only a small light field depolarisation. The operational limit has therefore been extended significantly, allowing efficient, parallel laser materials processing with a high-power picosecond laser. The calculation and implementation of binary Damman gratings for multi-beam laser processing is also shown to be useful at high power exposure.

In-situ repair of failed LiFePO4 cathode using residual Li- and C-containing impurities from active material separation process

Effectively recovering spent lithium-ion batteries can reduce resource waste and environmental pollution. LiFePO4 (LFP) batteries have been widely used in new energy vehicles. The main reason for the performance degradation of LFP cathodes is the loss of Li, oxidation of Fe, and the destruction of crystal structure and surface carbon layer. Here, an in-situ repair strategy of high-temperature calcination, using impurities remaining in cathode blackmass (e.g., LiPF6, LiPO3, Fe2O3, acetylene black, binder, and electrolyte) as raw materials, was proposed. During the calcination process, the residual LiPF6 is converted into Li, acting as a lithium source to fill the vacancies. The residual binder and electrolyte are pyrolyzed into amorphous carbon and carbon nanotubes, which deposit on the LFP particles to repair the missing carbon layer and enhance the conductivity of the electrode material. The pyrolytic carbon and residual acetylene black can provide a reducing atmosphere, converting Fe3+ to Fe2+. Additionally, the residual LiPO3 and Fe2O3 impurities undergo recrystallization forming new LFP. The failed LFP was restored to the same level as commercial LFP by calcining at 750 °C for 3 h. This in-situ repair strategy reduces the input of raw materials, providing a valuable reference for large-scale recycling of lithium batteries.

Silver-induced layer exchange and crystallization of a-Si films investigated using in situ scanning transmission electron microscopy

Silver-induced layer exchange and crystallization of a-Si films investigated using <i>in situ</i> scanning transmission electron microscopy

Friends not Foes: Exfoliation of Non-van der Waals Materials.

ConspectusTwo-dimensional materials have been a focus of study for decades, resulting in the development of a library of nanosheets made by a variety of methods. However, many of these atomically thin materials are exfoliated from van der Waals (vdW) compounds, which inherently have weaker bonding between layers in the bulk crystal. Even though there are diverse properties and structures within this class of compounds, it would behoove the community to look beyond these compounds toward the exfoliation of non-vdW compounds as well. A particular class of non-vdW compounds that may be amenable to exfoliation are the ionically bonded layered materials, which are structurally similar to vdW compounds but have alkali ions intercalated between the layers. Although initially they may have been more difficult to exfoliate due to a lack of methodology beyond mechanical exfoliation, many synthesis techniques have been developed that have been used successfully in exfoliating non-vdW materials. In fact, as we will show, in some cases it has even proven to be advantageous to start the exfoliation from a non-vdW compound.The method we will highlight here is chemical exfoliation, which has developed significantly and is better understood mechanistically compared to when it was first conceived. Encompassing many methods, such as acid/base reactions, solvent reactions, and oxidative extractions, chemical exfoliation can be tailored to the delamination of non-vdW materials, which opens up many more possibilities of compounds to study. In addition, beginning with intercalated analogues of vdW materials can even lead to more consistent and higher quality results, overcoming some challenges associated with chemical exfoliation in general. To exemplify this, we will discuss our group's work on the synthesis of a 1T'-WS2 monolayer ink. By starting with K0.5WS2, the exfoliated 1T'-WS2 nanosheets obtained were larger and more uniform in thickness than those from previous syntheses beginning with vdW materials. The crystallinity of the nanosheets was high enough that films made from this ink were superconducting. We will also show how soft chemical methods can be used to make new phases from existing compounds, such as HxCrS2 from NaCrS2. This material was found to have alternating amorphous and crystalline layers. Its biphasic structure improved the material's performance as a battery electrode, enabling reversible Cr redox and faster Na-ion diffusion. From these and other examples, we will see how chemical exfoliation of non-vdW materials compares to other methods, as well as how this technique can be further extended to known compounds that can be deintercalated electrochemically and to quasi-one-dimensional crystals.

Defect characterizations of N-rich GaNAs ternary alloys

This paper presents a comprehensive analysis of defects in As-diluted GaN alloys. GaNAs crystal layers with an arsenic content of 1.8, 2.9, 4.1, and 5.5 % are grown on GaN buffer layers using the metalorganic vapour-phase epitaxy (MOVPE) method. Since these alloys have potential in electronics due to the modification of the electronic structure caused by As, it is extremely important to determine their quality. Complementary techniques for the characterization of the alloys are used. Densities of screw and edge dislocations are obtained using X-ray diffraction measurements performed, respectively, from the surface and edge of samples. In turn, a population of vacancies is determined by Doppler broadening variable energy positron annihilation spectroscopy (DB-VEPAS) and variable energy positron lifetime positron annihilation spectroscopy (VEPALS), which provide the distribution of vacancies as a function of depth. An increase in dislocation density is observed accompanied by a rise in the concentration of vacancy agglomerations and reduction in Ga-vacancy-hydrogen associates in the function of As-content.

Liquid-Crystalline Photonic Sandwich: Electroresponsive Colloids of Clay Nanosheets Loading Photofunctional Dyes.

Colloidal clay nanosheets obtained by the delamination of layered crystals of smectite-type clay minerals in water form liquid crystals because of their shape anisotropy. Loading of organic dyes onto the liquid crystalline clay nanosheets will enable novel photonic materials, where photofunctions of the loaded dye are controlled by the liquid crystallinity of the clay nanosheets. However, adsorption of organic dyes onto the nanosheets renders the nanosheet surfaces hydrophobic, and consequently, colloidal stability of the nanosheets is lost. In this study, this drawback is overcome by sandwiching cationic stilbazolium dyes between a pair of synthetic fluorohectorite nanosheets. This is realized by the preparation of stilbazolium-clay second-stage intercalation compounds characterized by intercalation of dye cations into every other interlayer space of the hectorite clay, where nonintercalated interlayer spaces are occupied by Na+ ions. The second-stage intercalation compounds are obtained by partial ion exchange of mother clay mineral incorporating Na+ ions in all of the interlayer spaces and delaminated from the Na+-containing interlayer spaces to form clay nanosheets sandwiching the dye molecules. Aqueous colloids of the dye-sandwiching clay nanosheets form colloidal liquid crystals, and the dye-sandwiching liquid crystalline clay nanosheets respond to an applied AC electric field to be aligned parallel to the electric field. The assembled structure of the dye-sandwiching clay nanosheets under the electric field is characterized by aligned discrete clay platelets, which is somewhat different from that of a colloidal liquid crystal of clay nanosheets without dye loading characterized by macroscopic liquid crystalline domains up to submillimeters. The electric alignment of the clay nanosheets induces alteration of light absorption of the sandwiched stilbazolium molecules, which verifies a strategy of constructing stimuli-responsive photonic materials of clay-organic hybrids.

Crystal layer growth with embedded carbon-based particles from effervescent tablet-based nanofluids

Crystallization occurs as dissolved substances gradually solidify into crystal layers within a liquid, which can increase the capability of fluids to transfer heat. In this study, the growth of crystal layer in nanofluids produced from carbon-based effervescent tablets was examined. The tablets were fabricated by combining multi-walled carbon nanotubes (MWCNTs), sodium dodecyl sulfate (SDS), sodium phosphate monobasic (NaH2PO4), and sodium carbonate (Na2CO3). The effervescent tablets were formulated with MWCNTs, NaH2PO4, and Na2CO3 at a weight ratio of 1:5.1:2.26, respectively. These tablets were then immersed in distilled water (DW) and seawater (SW) to produce 0.05 vol.% to 0.15 vol.% MWCNT suspensions. Then, the dispersion stability, thermal conductivity, and crystal layer growth of the nanofluids were characterized. The results showed that the DW-based nanofluids were more stable than their SW-based counterparts. Additionally, the 0.05 vol.% DW-based suspension exhibited greater long-term stability than those of the 0.15 vol.% suspensions, whereas the SW-based nanofluid exhibited the opposite behaviour. The greatest increases in thermal conductivity were 3.29% and 3.13% for 0.15 vol.% MWCNTs in DW and SW, respectively. The crystallization process occurred in nanofluids that contained more than 0.05 vol.% MWCNTs and exhibited a greater growth rate in SW-based suspensions with high effervescent agent concentrations.

High-Q film bulk acoustic resonator with high quality AlN film based on transfer method

Thin film bulk acoustic resonator (FBAR) with high quality factor (Q) is preferred for many communication applications. AlN film deposited in conventional FBAR fabrication process is poor, resulting in unsatisfactory device performance. This study demonstrated the comparison of two Si-substrate FBARs, adopting the same AlN deposition process by physical vapor deposition (PVD) method, however using different device fabrication method. Instead of depositing AlN film on Mo/SiO2/Si substrate in existing fabrication process, we deposited AlN directly on Si substrate by PVD to get better crystal quality piezoelectric layer of the FBAR. The full width at half maximum (FWHM) of rocking curve and surface roughness of AlN directly deposited on Si substrate are 1.4° and 1.96 nm, while those of AlN deposited on Mo/SiO2/Si substrate are 8.5° and 5.54 nm, respectively, indicating AlN deposited directly on Si substrate has a better crystal quality than that on Mo/SiO2/Si substrate. The dielectric loss of FBAR using AlN developed on Si substrate decreases from 0.4 Ω to 0.11 Ω leading to the increase of Q m from 470 to 830. By preserving the high quality AlN deposited on Si substate with film transfer method, the FBAR device enjoys an increasing of Q-values as high as 76%.

The nontrivial effects of annealing on superconducting properties of Nb single crystals

The effect of annealing on the superconducting properties of niobium single crystals was studied using optical, magnetic, and scanning tunneling microscopy (STM) methods. Pieces of the same crystal boule were studied before and after the annealing at 800 ∘C , 1400 ∘C , and near the melting point of niobium (2477 ∘C ). The initial samples had a high hydrogen content and low-temperature imaging revealed large hydrides (hundreds of micrometers) appearing below 190 K. The formation of these large precipitates is already completely suppressed by annealing at 800 ∘C . However, the overall superconducting properties of the annealed samples did not improve and, in fact, worsened. In particular, the superconducting transition temperature decreased, the upper critical field increased, and the pinning strength increased. In the STM study, the sample was annealed initially at 400 ∘C , measured, annealed at 1700 ∘C , and measured again. The STM revealed a ‘dirty’ superconducting gap with a significant spatial variation in tunneling conductance after annealing at 400 ∘C . The clean gap was recovered after annealing at 1700 ∘C . This is likely due to oxygen redistribution near the surface, which is always covered by oxide layers in as-grown crystals. Our results indicate that vacuum annealing at least up to 1400 ∘C , while removing a large percentage of hydrogen, introduces additional nanosized defects, likely hydride precipitates, that act as efficient pair-breaking and pinning centers. The dimensionless scattering rate is estimated to have increased from Γ=0.2 to about Γ=0.4 after annealing at 1400 ∘C . These results on single crystals differ drastically from those obtained in polycrystalline bulk niobium (i.e. cut from superconducting radio-frequency cavities), where annealing is known to have a significant positive effect that is attributed to the improvement of the crystalline structure masking the more subtle influence of the hydrides.

Versatile Method for Preparing Two-Dimensional Metal Dihalides.

Ever since the ground-breaking isolation of graphene, numerous two-dimensional (2D) materials have emerged with 2D metal dihalides gaining significant attention due to their intriguing electrical and magnetic properties. In this study, we introduce an innovative approach via anhydrous solvent-induced recrystallization of bulk powders to obtain crystals of metal dihalides (MX2, with M = Cu, Ni, Co and X = Br, Cl, I), which can be exfoliated to 2D flakes. We demonstrate the effectiveness of our method using CuBr2 as an example, which forms large layered crystals. We investigate the structural properties of both the bulk and 2D CuBr2 using X-ray diffraction, along with Raman scattering and optical spectroscopy, revealing its quasi-1D chain structure, which translates to distinct emission and scattering characteristics. Furthermore, microultraviolet photoemission spectroscopy and electronic transport reveal the electronic properties of CuBr2 flakes, including their valence band structure. We extend our methodology to other metal halides and assess the stability of the metal halide flakes in controlled environments. We show that optical contrast can be used to characterize the flake thicknesses for these materials. Our findings demonstrate the versatility and potential applications of the proposed methodology for preparing and studying 2D metal halide flakes.

A recyclable, interchangeable optical switch with a PDLC-PVA-PSCLC structure and a low-voltage drive system

ABSTRACT Polymer dispersed liquid crystals (PDLC) and polymer stabilised cholesteric liquid crystals (PSCLC) are an indispensable class of electrically switchable materials, which have been widely applied in the fabrication of efficient and systematic smart windows. And doping nanoparticles in PDLC films can greatly improve their properties. In this study, PDLC films doped with zirconia nanoparticles were prepared by polymerisation-induced phase separation (PIPS) method, PSCLC films with nematic liquid crystals as the main part (reflecting wavelengths in the range of 400–600 nm) were prepared by UV curing method, and a novel optical switch was developed by combining these two liquid crystal films. The optimal bilayer sample was developed through a comparative analysis of properties among samples with varying formulations for each liquid crystal layer. This study represents a novel advancement in PSCLC and nanoparticle-doped PDLC bilayer structures, showcasing fully actuatable properties in the visible wavelength range. These structures exhibit excellent electro-optical properties and demonstrate stable, sustainable performance that can be regenerated. The findings underscore the potential of PDLC and PSCLC for applications in smart curtains and flexible materials, opening up new avenues for innovative technological applications.

Long-Range Self-Hybridized Exciton-Polaritons in Two-Dimensional Ruddlesden-Popper Perovskites.

Lead halide perovskites have emerged as platforms for exciton-polaritonic studies at room temperature, thanks to their excellent photoluminescence efficiency and synthetic versatility. In this work, we find proof of strong exciton-photon coupling in cavities formed by the layered crystals themselves, a phenomenon known as the self-hybridization effect. We use multilayers of high-quality Ruddlesden-Popper perovskites in their 2D crystalline form, benefiting from their quantum-well excitonic resonances and the strong Fabry-Pérot cavity modes resulting from the total internal reflection at their smooth surfaces. Optical spectroscopy reveals bending of the cavity modes typical for exciton-polariton formation, and absorption and photoluminescence spectroscopy shows splitting of the excitonic resonance and thickness-dependent peak positions. Strikingly, local optical excitation with energy below the excitonic resonance of the flakes in photoluminescence measurements unveils the coupling of light to in-plane polaritonic modes with directed propagation. These exciton-polaritons exhibit high coupling efficiencies and extremely low loss propagation mechanisms, which are confirmed by finite difference time domain simulations. Thus, we prove that mesoscopic 2D Ruddlesden-Popper perovskite flakes represent an effective but simple system to study the rich physics of exciton-polaritons at room temperature.

Evolution of macromolecular structure during coal oxidation via FTIR, XRD and Raman

The analysis of the macromolecular structure and morphology in coal during oxidation is the basis to explore the mechanism of spontaneous combustion. To explore the evolutionary rules of coal macromolecular structure during oxidation, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Raman Spectroscopy (Raman) were employed to analyze the coal samples with different oxidation degrees. The results revealed that the oxidation action led to the decrease of the aliphatic structures and aromatic hydroxyl groups in coal, while promoting the formation of oxygen-containing functional groups and aromatic structures. It also led to a relative increase of free hydroxyl groups linked to hydrogen bonds. The aromatic layer spacing (d002) decreased with increasing oxidation degree, while the microcrystal stacking height (Lc), the aromatic layer diameter (La), the average number of crystal stacking layers (n) generally increased. It indicated that small aromatic ring molecules in coal could undergo continuous polymerization during oxidation to form a single aromatic layer structure. The variation of Raman spectrum parameters exhibited a consistent decreasing trend in WD/WG, ID/IG, AD/AG, and A(GR+SL)/AG value, indicating an increase in the vibration of sp2 hybridization carbon atoms within the lattice structure of coal. Conversely, PG-D, AS/AD and A(GR+VL+VR)/AD value increased overall, suggesting that small aromatic rings decreased in content during oxidation while polymerizing into larger aromatic rings. The coal structure underwent a brief stage of disordered evolution during oxidation, followed by removal of impurity structures and condensation of aromatic structures due to increasing oxidation temperatures, ultimately leading to a highly ordered crystalline state. The oxidation process significantly influenced the development of coal's aromatic structure, particularly in less metamorphic coal. The research findings provide a theoretical basis for analyzing the underlying mechanism behind spontaneous combustion induced by coal oxidation.

In Situ Visual Observation of Surface Energy-Controlled Heterogeneous Nucleation of Metal Nanocrystals.

Electrochemical growth of metal nanocrystals is pivotal for material synthesis, processing, and resource recovery. Understanding the heterogeneous interface between electrolyte and electrode is crucial for nanocrystal nucleation, but the influence of this interaction is still poorly understood. This study employs advanced in situ measurements to investigate the heterogeneous nucleation of metals on solid surfaces. By observing the copper nanocrystal electrodeposition, an interphase interaction-induced nucleation mechanism highly dependent on substrate surface energy is uncovered. It shows that a high-energy (HE) electrode tended to form a polycrystalline structure, while a low-energy (LE) electrode induced a monocrystalline structure. Raman and electrochemical characterizations confirmed that HE interface enhances the interphase interaction, reducing the nucleation barrier for the sturdy nanostructures. This leads to a 30.92-52.21% reduction in the crystal layer thickness and a 19.18-31.78% increase in the charge transfer capability, promoting the formation of a uniform and compact film. The structural compactness of the early nucleated crystals enhances the deposit stability for long-duration electrodeposition. This research not only inspires comprehension of physicochemical processes correlated with heterogeneous nucleation, but also paves a new avenue for high-quality synthesis and efficient recovery of metallic nanomaterials.

Acoustically driven ferromagnetic resonance in YIG thin films

Acoustically driven ferromagnetic resonance (ADFMR) is a platform that enables efficient generation and detection of spin waves via magnetoelastic coupling with surface acoustic waves (SAWs). While previous studies successfully achieved ADFMR in ferromagnetic metals, there are only few reports on ADFMR in magnetic insulators such as yttrium iron garnet (Y3Fe5O12, YIG) despite more favorable spin wave properties, including low damping and long coherence length. The growth of high-quality YIG films for ADFMR devices is a major challenge due to poor lattice-matching and thermal degradation of the piezoelectric substrates during film crystallization. In this work, we demonstrate ADFMR of YIG thin films on LiNbO3 (LNO) substrates. We employed a SiOx buffer layer and rapid thermal annealing for crystallization of YIG films with minimal thermal degradation of LNO substrates. Optimized ADFMR device designs and time-gating measurements were used to enhance the ADFMR signal and overcome the intrinsically low magnetoelastic coupling of YIG. YIG films have a polycrystalline structure with an in-plane easy direction due to biaxial stresses induced during cooling after crystallization. The YIG device shows clear ADFMR patterns with maximum absorption for H ≈ 160 mT parallel to SAW propagation, which is consistent with our simulation results based on existing theoretical models. These results expand possibilities for developing efficient spin wave devices with magnetic insulators.