Within the phase-field framework, matrix cracking and interfacial debonding in composites are simultaneously captured by introducing dual phase-field variables. To smooth a sharp interface, an interface-related phase-field variable is defined, and equivalent material parameters are formulated using interpolation functions that depend on the interface phase-field distribution. On the basis of the phase-field cohesive zone model, a crack phase-field variable is employed to capture material failure, enabling the characterization of various interfacial failure modes and quantification of the effect of interface strength on fracture behavior. Numerical results demonstrate that the interpolation function order significantly affects structural response: higher-order interpolations expand the low-fracture-energy region near the interface, reduce the predicted peak load, and promote a transition in the crack path from interfacial debonding to matrix cracking. This transition is attributed to the smoother variations in the local stiffness and fracture resistance introduced by higher-order interpolations. Moreover, increasing the interface strength enhances the load-bearing capacity and drives the fracture mode toward matrix-dominated cracking. For fiber-reinforced composite cases, the results obtained from higher-order interpolations closely match those derived from cohesive element models, validating the proposed approach. This framework offers a robust computational tool for investigating the interaction between interfacial debonding and matrix cracking, and provides deeper understanding of how interface parameterization influences fracture behavior in composites.

Development of a new THINC/WLIC method based on a separate evaluation of the geometrical fidelity and the interface sharpness

VOF and sharp interface CFD analyses of a liquid methane self-pressurization experiment in 1 g and microgravity

As dynamic random-access memory continues to scale down, the feasible physical thickness of the capacitor dielectric layer continuously decreases, thus, controlling the low-k interfacial layer formed at the ZrO2 dielectric/TiN electrode interface is becoming crucial. The interfacial layer reduces the capacitance density and increases the leakage current density, and both of them contribute to the degradation of the overall properties of the capacitor. In this study, two precursors were compared: the commonly used Cp-based Zr precursor, Cp-Zr(NMe2)3 [Cp-Zr] and the novel MePrCp-Zr(NMe2)3 [MePrCp-Zr] precursor, with the two terminal hydrogens of the Cp ligand substituted with Me and Pr groups. MePrCp-Zr was confirmed to suppress the formation of low-k interfacial layers such as TiOx or TiOxNy at the initial ZrO2 growth stage, owing to its higher reactivity than Cp-Zr. Furthermore, analysis of oxidation behavior using TiN and Ru bottom electrodes clearly revealed that the application of MePrCp-Zr led to improved interfacial sharpness compared to Cp-Zr. Electrical properties also confirmed enhanced interfacial properties, indicating that the equivalent oxide thickness decreased by 0.38 nm with the MePrCp-Zr precursor compared to Cp-Zr. This ligand-engineering strategy provides a scalable approach to achieving ultrathin high-k dielectrics with stable interfaces, enabling reliable capacitor integration for next-generation DRAM and advanced logic technologies.

An analytical model for the nucleation of edge misfit dislocations in cylindrical core-shell nanowires with a diffuse interface boundary is developed. The model is formulated within the framework of linear isotropic elasticity theory and accounts for the interplay between the nanowire’s geometry, interface diffuseness, and lattice mismatch. By evaluating the total energy change associated with dislocation formation, we systematically analyze the dependence of energetic favorability of dislocation nucleation on the core/shell radius ratio, diffuse interface width, and misfit parameter. The results demonstrate that sharp interfaces maximize the energy gain from dislocation formation, whereas diffuse interfaces suppress it, particularly in nanowires with thin cores. The optimal dislocation nucleation site is primarily governed by geometry features and only weakly influenced by misfit parameter. A critical misfit parameter is identified, above which the nanowire coherent state becomes unstable. The analysis reveals that while broader diffuse interfaces reduce the tendency for relaxation process, increased lattice mismatch promotes it.

AlGaN-based deep-ultraviolet vertical-cavity surface-emitting lasers (DUV VCSELs) have shown a great application potential in optical atomic clocks, maskless photolithography, etc. Nevertheless, the uncontrolled cavity length-induced detuning issue, i.e., the difference between the resonance wavelength and gain peak, severely impairs the device performance. Herein, a DUV-VCSEL strategy featuring the uniform nanometer-class control of the cavity length in a 4-in wafer is proposed in the DUV framework based on GaN templates, which ensures the wafer-scale removal of sapphire substrates by laser lift-off, and then provides space for the subsequent deposition of dielectric distributed Bragg reflector (DBR). It is more significant that the strategy brings about a GaN/AlGaN sharp interface with an Al composition difference up to 80%, whereby self-terminated etching with an ultrahigh selectivity of 100:1 is achieved. The cavity length is hence accurately determined by epitaxy itself instead of the fabrication process, so as to minimize the detuning. As such, 285.6-nm optically pumped DUV VCSELs with double dielectric DBRs are fabricated, exhibiting a record low threshold of 0.38 MW cm-2 and a narrow linewidth of 0.11nm. What's more, the lasing wavelength varies within 1.9nm across the 4-in wafer, indicating a cavity length variation of only 0.81%.

Polymer multilayer films with functional tie layers are used in a variety of applications. The layer adhesion in these multilayer films is known to degrade upon stretching of the multilayer structure, which is required for certain applications. Although the loss of adhesion strength is empirically observed, the molecular basis or mechanism of this adhesion loss is unknown. In this research, we investigated buried interfaces of polymer multilayer thin films with and without stretching, in situ, to understand the reason for adhesion loss using sum frequency generation (SFG) vibrational spectroscopy. The unstretched film exhibits no SFG signals in the C═O stretching frequency region at the ethylene-vinyl alcohol copolymer/maleic anhydride (MAH) grafted polyethylene interface, indicating disordered interfacial C═O groups. This is because the C═O groups are randomly orientated at the interface due to the interfacial diffusion and interfacial chain entanglement of the two polymer materials, leading to a "diffused" interface instead of a distinct or sharp interface. For the 3× and 6× stretched films, SFG C═O stretching signals could be easily detected from the buried interfaces. Analysis of the SFG spectra collected from orthogonal directions showed that the azimuthal orientations of interfacial C═O groups were randomly distributed without a preferred alignment along the stretching direction. Further analysis of the SFG results suggests that the loss of physical entanglement at the interface, rather than interfacial chemical bond breaking, was the reason for the adhesion decrease in stretched films. This research provides important insights into future polymer thin-film material design and performance improvements.

Abstract In this work, we develop a novel technique for reconstructing images from projection-based nano- and microtomography.
Our contribution focuses on enhancing reconstruction quality, particularly for specimen composed of homogeneous material phases connected by sharp edges. This is accomplished by training a neural network to identify edges within subpictures. The trained network is then integrated into a mathematical optimization model, to reduce artifacts from previous reconstructions. To this end, the optimization approach favors solutions according to the learned predictions, however may also determine alternative solutions if these are strongly supported by the raw data. Hence, our technique successfully incorporates knowledge about the homogeneity and presence of sharp edges in the sample and thereby eliminates blurriness. Our results on experimental datasets show significant enhancements in interface sharpness and material homogeneity compared to benchmark algorithms. Thus, our technique produces high-quality reconstructions, showcasing its potential for advancing tomographic imaging techniques.

Kinetic multiphase flow solvers have recently demonstrated exquisitely complex and turbulent fluid phenomena involving splashing and bubbling. However, they require full simulation of both the liquid phase and the air to capture a large spectrum of fluid behaviors. Moreover, they rely on diffuse interface tracking to properly account for the interfacial forces involved in fluid-air interactions. Consequently, simulating visually appealing fluids is extremely compute intensive given the required resolution to capture small bubbles, and foam simulation is unattainable with this family of methods. While water simulation involves density and viscosity differences between the two phases so large that one can safely ignore the dynamics of air, so-called kinetic free-surface solvers that only consider the liquid motion have been unable to reproduce the full gamut of turbulent fluid behaviors, being often unstable for even moderately complex scenarios. By revisiting kinetic solvers using sharp interfaces and incorporating recent advances in single-phase and multiphase LBM solvers, we propose a free-surface kinetic solver, which we call HOME-FREE LBM, that not only handles turbulence, glugging, and bubbling, but even foam where bubbles stick to each other through surface tension. We demonstrate that our fluid simulator allows for fast and robust bubble growth, breakup, and coalescence, at a fraction of the computational time that existing CG fluid solvers require.

Sharp interface CFD analysis of noncondensable gas effects on 1g and microgravity tank self-pressurization and pressure control

Nanofluids are widely applied in spray cooling, combustion, and coating processes, where nanoparticle dispersion modifies base fluid rheology and influences atomization behavior. Accurate modeling requires computational fluid dynamics (CFD) approaches that capture gas–liquid interactions, nanoparticle transport, and sub-grid effects including interphase momentum exchange, particle collisions, and Brownian motion. This study presents a novel three-phase solver developed in OpenFOAM based on multiphase mixture theory, incorporating the volume of fluid (VOF) method enhanced with isoAdvection for sharp interface reconstruction, adaptive mesh refinement (AMR) for high-resolution atomization, and closures for gravity, buoyancy, centrifugal forces, turbulent and shear-induced diffusion, van der Waals forces, and particle collisions. Nanoparticle rheology is modeled via kinetic theory. Validation was conducted in two stages. Sedimentation simulations for nanoparticle mass fractions of 1–7 wt. % predicted base fluid–nanofluid (B-N) interface and sediment height with maximum relative errors of 2.03% and 3.06%, respectively, and experimental relative standard deviations below 0.93% (B-N interface) and 3.87% (sediment height). Water primary atomization simulations benchmarked the isoAdvection-based solver against the standard OpenFOAM interIsoFoam solver and a multidimensional universal limiter for explicit solution (MULES)-based solver. Key performance parameters, including spray cone angle, liquid film thickness, and breakup length, were accurately captured, with maximum errors of 3.98% (isoAdvection) and 3.40% (interIsoFoam), outperforming MULES (7.79%). Overall, the developed solver demonstrates robust, quantitative agreement with experiments, accurately capturing nanoparticle transport, sedimentation dynamics, and primary atomization features in free-surface nanofluid flows under atmospheric and isothermal conditions.

Analogous to the pivotal SiO2/Si junction in modern electronics, the β-Bi2SeO5/Bi2O2Se architecture has been demonstrated to enhance the performance of electronic devices. However, its potential to improve the optoelectronic properties of Bi2O2Se, such as responsivity and detectivity, remains unexplored. The photodetection performance of Bi2O2Se is primarily limited by intrinsic selenium vacancies at its surface, which lead to low photocurrent and instability. To address this, a defect-engineered β-Bi2SeO5/Bi2O2Se heterojunction is constructed with an atomically sharp interface via a developed UV-assisted oxidation strategy. This heterostructure successfully suppresses surface vacancies while enabling dual functionality-surface passivation and photoactive charge separation, resulting in substantially enhanced optoelectronic performance. First-principles calculations confirm a stable type-II band alignment with interfacial transitions enabling efficient carrier dissociation. The visible-near-infrared transparency and high-k of β-Bi2SeO5 further enable top-gated phototransistors with dynamically tunable photoresponse, achieving the largely improved metrics of responsivity (1.2 × 104 A W-1), detectivity (1.5×1013 Jones), and on/off ratio (2.3× 106). Additionally, by using thermal scanning probe lithography, a high-resolution (pixel pitch = 6.5 µm) β-Bi2SeO5/Bi2O2Se phototransistor array is fabricated and its imaging capabilities are demonstrated. The results establish an effective defect-engineered strategy with in situ large-area growth capability of β-Bi2SeO5 and high-resolution device patterning, making β-Bi2SeO5/Bi2O2Se a promising photoresponsive platform for advanced optoelectronic devices.

Abstract The development of highly efficient semiconducting materials is essential for achieving the high‐yield and stable hydrogen and/or oxygen evolution reactions (HER/OER) in photoelectrochemical (PEC) water splitting reactions. The SrTiO 3 ‐TiO 2 eutectic compound has recently emerged as a perspective material with extraordinary activities in the PEC field due to the unique crystallographic and electronic properties caused by the large number of oxygen vacancies in the bulk. In the present study, different experimental techniques (XPS, SEM/EDX, TEM/EDX) are used to provide a detailed investigation of the changes in the structural and electronic properties of the SrTiO 3 ‐TiO 2 eutectic upon annealing under various gaseous environments (in vacuum, air, oxygen, argon). These results demonstrate that thermal annealing in different environments significantly enhances the formation of a sharp interface between the two crystalline phases and allows to control the concentration of the oxygen vacancies within the eutectic material.

Abstract The Cahn–Hilliard model with reaction terms can lead to situations in which no coarsening is taking place and, in contrast, growth and division of droplets occur which all do not grow larger than a certain size. This phenomenon has been suggested as a model for protocells, and a model based on the modified Cahn–Hilliard equation has been formulated. We introduce this equation and show the existence and uniqueness of solutions. Then, formally matched asymptotic expansions are used to identify a sharp interface limit using a scaling of the reaction term, which becomes singular when the interfacial thickness tends to zero. We compute planar solutions and study their stability under non-planar perturbations. Numerical computations for the suggested model are used to validate the sharp interface asymptotics. In addition, the numerical simulations show that the reaction terms lead to diverse phenomena such as growth and division of droplets in the obtained solutions, as well as the formation of shell-like structures.

High-quality epitaxial GeSn films grown directly on Si substrates are highly desirable for integrated photonics applications, as eliminating the intermediate buffer layer simplifies device fabrication. A ∼1 μm thick, epitaxial Ge0.95Sn0.05 film was grown directly on a (001) Si substrate by remote plasma-enhanced chemical vapor deposition using a two-step process: an ultra-thin GeSn initiation layer was first deposited at 421 °C for 1 min, followed by the main film deposition at 330 °C for 85 min. Here, we analyze the detailed microstructure of the GeSn film using atomic force microscopy, Raman spectroscopy, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The Ge0.95Sn0.05 film exhibits a hill and valley-like surface morphology and a sharp interface with the substrate. It consists of a ∼150 nm bottom epilayer containing characteristic twin structures, and an ∼850 nm upper epilayer composed of dense, vertically oriented columnar structures with lateral dimensions ranging from approximately 200–300 nm. These columns are bounded by vertically aligned interfaces composed of straight threading dislocations that extend from near the substrate interface through the film to the surface. The Burgers vectors of the threading dislocations were identified as 1/2[110] and/or 1/2[−110]. The columnar boundaries, rich in strain, are responsible for the development of the observed rugged, hill and valley-like surface topography. The formation of the threading dislocations is likely attributed to local fluctuations in Sn content. The observed microstructure offers valuable insight into the growth mechanism, which can be leveraged to optimize the process for enhanced film quality suitable for device applications.

We introduce an unfitted Nitsche finite element method with a new ghost-penalty stabilization based on local projection of the solution gradient. The proposed ghost-penalty operator is straightforward to implement, ensures algebraic stability, provides an implicit extension of the solution beyond the physical domain, and stabilizes the numerical method for problems dominated by transport phenomena. This paper presents both a sharp interface version of the method and an alternative diffuse interface formulation designed to avoid integration over implicitly defined embedded surfaces. A complete numerical analysis of the sharp interface version is provided. The results of several numerical experiments support the theoretical analysis and illustrate the performance of both variants of the method.

Co-existence of planar and non-planar traveling waves in a sharp interface model

Abstract In this study, we propose a parametric finite element method for a degenerate multi-phase Stefan problem with triple junctions. This model describes the energy-driven motion of a surface cluster whose distributional solution was studied by Garcke and Sturzenhecker. We approximate the weak formulation of this sharp interface model by an unfitted finite element method that uses parametric elements for the representation of the moving interfaces. We establish existence and uniqueness of the discrete solution and prove unconditional stability of the proposed scheme. Moreover, a modification of the original scheme leads to a structure-preserving variant, in that it conserves the discrete analogue of a quantity that is preserved by the classical solution. Some numerical results demonstrate the applicability of our introduced schemes.

The paper is devoted to the study of the two-phase free boundary problem for nonlinear partial differential equations describing the evolution of a foam drainage in the one dimensional case which was proposed by Goldfarb et al. in 1988 in order to investigate the flow of a liquid through channels (Plateau borders) and nodes (intersections of four channels) between the bubbles, driven by gravity and capillarity. In a series of papers, the authors have already solved the same problems without free boundary and with free boundary situated at the lower and the upper parts in the foam column, respectively. In this paper it is shown that the free boundary problem for the foam drainage equations with a sharp interface between dry and wet foams admits a unique global-in-time classical solution; this is done by a standard classical mathematical method, the maximum principle, and the comparison theorem. Moreover, the existence of the steady solution and its stability are shown.

We study locomotion of a model crawler corresponding to a deforming upper boundary of finite length above a thin Newtonian fluid film whose viscosity varies spatially. We first derive a general locomotion velocity formula with fluid viscosity variations via the lubrication theory. For further analysis, the surface of the crawler is described by a combination of transverse and longitudinal traveling waves and we find that under a uniform viscosity a transverse wave results in a retrograde crawler, while a longitudinal wave leads to a direct crawler. We then analyze the time-averaged locomotion behaviors under two scenarios: (i) a sharp viscosity interface and (ii) a linear viscosity gradient. Using the asymptotic expansions of small surface deformations and the method of multiple timescale analysis, we derive an explicit form of the average velocity that captures nonlinear, accumulative interactions between the crawler and the spatially varying environment. (i) In the case of a viscosity interface, the time-averaged speed of the crawler is always slower than that in the uniform viscosity, for both the transverse and longitudinal wave cases. Notably, the speed reduction is most significant when the crawler's front enters a more viscous layer and the crawler's rear exits from the same layer. (ii) In the case of a viscosity gradient, the crawler's speed becomes slower for the transverse wave, while for the longitudinal wave, the locomotion speed does not change significantly. Our analysis illustrates the fundamental importance of interactions between a locomotor and its environment, and separating the timescale behind the locomotion.