Abstract Phase selection among competing stoichiometric compounds during nonequilibrium vapor-phase growth remains a fundamental challenge because experimentally accessible growth parameters ultimately influence phase formation through both thermodynamic driving forces and atomic-scale kinetic processes. Here, we investigate phase selection between SnSe and SnSe2 during low-pressure chemical vapor deposition (CVD) by integrating systematic growth experiments, first-principles thermodynamic calculations, and ab initio molecular dynamics (AIMD) simulations. Systematic regulation of the relative Sn/Se chemical environment and growth temperature establishes distinct SnSe- and SnSe2-dominant growth regimes. Thermodynamic calculations show that SnSe is preferentially stabilized under Sn-rich conditions with low Se chemical potential, whereas increasing the Se chemical potential shifts the thermodynamic preference toward SnSe2. Complementary atomistic simulations reveal that increasing Se availability progressively promotes SnSe2-like local coordination, while elevated temperature enhances Sn−Se interdiffusion and redistributes Se toward more spatially dispersed, locally Se-deficient configurations. Building on the established phase-selective growth conditions, we further demonstrate independent thickness tunability through growth-time control, with SnSe and SnSe2 film thicknesses spanning 15−123 and 13.5−120 nm, respectively. Together, these results show that stoichiometry-dependent phase competition under nonequilibrium growth conditions reflects the combined effects of thermodynamic stability and atomic kinetics, while film thickness can be adjusted through growth-time control. These results provide insight into the relationship between growth conditions, phase selection, and film thickness in compositionally related layered chalcogenides.
Two-dimensional (2D) magnetic skyrmions hold great promise for next-generation high-density information storage, yet their low-dimensional behavior and controllable size remain challenging. Here, combining first-principles calculations and Monte Carlo simulations, we identify monolayer CrGaTe3, derived from the Ga2S3 structure, as a ferromagnetic half-metal and a robust platform for hosting topological spin textures. The system exhibits a substantial Dzyaloshinskii−Moriya interaction (DMI) of 2.36 m V, arising from intrinsic inversion asymmetry and strong spin−orbit coupling, alongside sizable Kitaev exchange and magnetic anisotropy. At zero field, the ground state adopts a Néel-type cycloid state, which evolves into stable skyrmion phases under moderate external magnetic fields. Remarkably, beyond field tuning, we find that biaxial strain not only modulates the skyrmion size but also induces skyrmion states under tensile conditions, offering an additional degree of freedom for topological phase engineering. Furthermore, our parameter-resolved analysis reveals that while DMI is pivotal for skyrmion nucleation, the Kitaev interaction and magnetic anisotropy collectively govern the size and density of the skyrmion lattice. These findings establish monolayer CrGaTe3 as a promising candidate for sub-10 nm spintronic devices and demonstrate that the synergy between intrinsic symmetry breaking and external stimuli provides a generalizable strategy for designing functional 2D magnets.
Directional charge transport is essential for efficient photocatalysis, yet carrier transfer in semiconductor nanocrystals is often random and limited by recombination. Although electron−phonon coupling strongly influences carrier dynamics, phonons are more commonly associated with energy dissipation than with enhanced charge transport. Here, we construct a ZnO vacancy homojunction composed of donor-type oxygen vacancies and acceptor-type zinc vacancies, establishing an intrinsic pathway for directional charge transfer. The resulting n−p junction introduces both an internal electric field and asymmetric lattice distortion, enabling phonon-assisted directional carrier transport under ultrasonication and leading to significantly enhanced photocatalytic performance in methylene blue degradation compared with conventional ZnO. Combined spectroscopic measurements, radical-trapping experiments, and density functional theory calculations reveal a phonon-enhanced directional charge-transfer mechanism. These findings provide a general strategy for regulating directional charge transport through lattice dynamics.
Abstract Dual-band electrochromic smart windows, capable of independently regulating visible and near-infrared solar radiation, offer an effective route toward reducing building/vehicle energy consumption. However, their practical implementation is often limited by slow switching kinetics, insufficient bistability, as well as challenges in fabricating polychromatic, uniform, and scalable electrochromic films with efficient ion and charge transport. Here, we report an interfacial self-assembly strategy to fabricate large-area polyaniline (PANI) thin films featuring a hierarchically porous architecture and thickness-dependent porosity gradient. The self-assembly process, driven by solvent exchange at the air–water interface and modulated by surfactant confinement, produces interconnected PANI nanoparticle networks with both in-plane hierarchical pores and out-of-plane structural gradation. This architecture facilitates electrolyte penetration and charge transport across the film thickness. As a result, the PANI films enable rapid and stable dual-band electrochromic modulation, exhibiting three distinct optical states (“bright”, “cool”, and “dark”) with independent control of visible and near-infrared transmittance. The assembled devices demonstrate fast response (coloration/bleaching times of 1.8/4 s at 633 nm and 1.2/3.6 s at 1200 nm), high coloration efficiency, and excellent optical bistability, together with effective indoor thermal regulation. These results establish interfacial self-assembly as a versatile approach for engineering functional polymer films for next-generation energy-efficient smart windows.
Abstract Composite electrodes containing physical mixtures (“blends”) of multiple active materials have generated commercial interest for lithium battery applications due to the possibility of enhanced electrochemical performance, which are not fully characterised. This investigation uses mixtures of well-known LiMn0.7Fe0.3PO4 (LMFP) and LiNi0.8Mn0.1Co0.1O2 (NMC) materials as a model blend system to investigate rate- and composition-dependent effects on performance. A combination of electrochemical and operando techniques reveals that deviations in performance with respect to the linear combination of the component materials originate from uneven current distribution, leading to different effective rates between components and spontaneous lithium-ion redistribution, commonly termed the “buffer effect”. Results of experiments using a specially adapted three-electrode setup show that the effective rates of the components vary considerably depending on the cell state of charge, with much higher effective rates being reached than the applied cell rate. The same setup allows the direction of lithium redistribution to be visualised when the system relaxes following a current pulse, and this directionality also varies with cell state of charge. Electrochemical investigations and Raman spectra reveal that blending reduces chemical sensitivity to ambient storage conditions and leads to reduced degradation by forming a protective LMFP layer around the more reactive NMC particles. Operando data shows that the blend components evolve largely as expected when taking into account their specific effective rates, in line with the materials retaining their individual electrochemical properties. This study highlights the importance of considering relative windows of electrochemical activity when selecting blend components and paves the way for future optimisation of electrode blends for high rate lithium-ion batteries.
