Photoemission yield spectroscopy in air was used to investigate the concentration-dependent threshold energy of photo-emission (ET) of methylene blue (MB) at the air/water interface under ambient conditions. Aqueous MB solutions of various concentrations were prepared. The results obtained showed that ET remained nearly constant at low bulk concentrations but decreased at higher concentrations, indicating changes in molecular packing at the interface. To understand the origin of the observed ET changes, we performed density functional theory calculations that included dispersion corrections and solvent effects. The lowest ionization potentials were found for dimer configurations, thus providing a qualitative explanation for the observed decrease in ET with increasing MB concentration.
With the increasing importance of topological materials in optoelectronic devices, the development of efficient and stable topological materials has become a research hotspot. To provide theoretical support for the design of functional optoelectronic devices, this study proposes a localized angular state (LAS) dipole-dipole interactions (DDI) and optical field distribution. This scheme adopts the non-equilibrium Green's function recursive method to calculate the electronic transport properties and clarify the electronic structural basis required for local angular poses vacancy defect control strategies, directly achieving precise localization and migration of angular states. In addition, a photonic crystal system is constructed to utilize DDI to verify the optical feasibility of LASs. The results showed that the conductivity peak of armchair T-shaped graphene reached 6.8 at a 90 degrees, and the density peak at a 60 degrees was about 0.25 states eV-1. When the vacancy defect density was 15 %, the light field intensity reached a peak of 3.2/3.1 a.u., with 4 LASs and a stability score of 9. This study validates the optical feasibility of high-order topological non-trivial phases and LASs, providing new ideas for the development of topological materials and the design of optoelectronic devices.
We demonstrate rotational anisotropy soft X-ray second harmonic generation (RA-SXSHG) using a free-electron laser, extending nonlinear X-ray spectroscopy into the symmetry-resolved regime with elemental specificity. By performing RA-SXSHG measurements on GaAs(001) as a function of sample azimuthal orientation, we have demonstrated that this technique can effectively probe the crystalline structure of the As ions. Our results validate that the extension of established rotational anisotropy second harmonic generation frameworks, conventionally developed in the optical wavelength regime, remains robust and predictive in the soft X-ray regime, with close correspondence between theoretical modeling and experimental data. We also find that this soft X-ray nonlinear optical method is highly sensitive to the electronic properties of the surface space-charge layer with element selection. These findings lay the theoretical foundation for RA-SXSHG and establish it as a powerful nonlinear X-ray spectroscopic technique for probing surfaces and buried interfaces with symmetry and element specificity.
We investigated the thickness-dependent structural evolution of Cu/Fe-Co(100) thin films grown by molecular beam epitaxy (MBE). At the initial stage of growth, Cu adopted a body-centered cubic (bcc) structure templated by the underlying FeCo substrate. Once the Cu thickness exceeded approximately 3 nm, a structural transformation into the face-centered cubic (fcc) phase was observed. The MBE-grown films exhibited interfacial dislocations and developed a disordered surface in the thickness range of 3-5 nm. Although metastable ultrathin bcc-Cu films on FeCo(100) grown by MBE are less stable than sputtered multilayers, MBE offers a unique advantage: it enables in-situ advanced characterization such as angle-resolved photoemission spectroscopy (ARPES) in the ultrathin regime around 1 nm. This capability is essential for designing high-performance devices and probing interface-driven electronic phenomena.
Thermal diffusion of indium (In) into ZnO nanoparticles (NPs) were examined to decrease sheet resistance values of ZnO NP layers sprayed on quartz substrates. NP layers made of as-synthesized ZnO NPs exhibited extremely high sheet resistance values. On the other hand, NP layers made of ZnO NPs with In diffusion, the sheet resistance showed large variation, and in particular, it decreased significantly showing a strong correlation with the water vapor contents in the gases during thermal diffusion. The sheet resistance value decreased down to the order of 105 Omega sq-1 (minimum value of 6 & times; 105 Omega sq-1). From X-ray diffraction, energy dispersive X-ray spectroscopy and photoluminescence analyses, the effects of the surface defects of ZnO NPs and the ambient water vapor in thermal diffusion process were discussed.
The stability of monolayer-thick Ag stripes formed on the Ni(110) surface was studied using first-principles calculations. The Ag stripes were found to be the aggregation of one-dimensional (1-D) silver (Ag) clusters along the [1 (1) over bar0] direction between the Ni(110) rows, and the clusters extended in the [001] direction to form stripes. Due to the large lattice mismatch between the adsorbed Ag and the Ni substrate, 1-D Ag clusters were not stable with more than seven atoms, and the edge atoms at the 1-D clusters tended to dissociate. The diffusion barriers for the dissociation of the 1-D Ag cluster edges were evaluated using the nudged elastic band method and found to be 0.41 eV for a two-Ag atom cluster (n = 2) and 0.14 eV for a ten-Ag atom cluster (n = 10). Considering surface relaxation of the substrate Ni atoms in the < 001 > directions, the diffusion barrier further decreased by similar to 0.06 eV, which explains the experimental scanning tunneling microscopy images. It was also found that 1-D Ag clusters aggregated to form stripes extending in the [001] direction due to the effect of substrate strain and the one dimensional band formation of Ag 5s-derived states in the stripe direction.
We investigate photoinduced carrier modulation in graphene field using nitrogen vacancy centers in nanodiamonds. The observed change in the Oersted magnetic field during measurement is attributed to laser-induced molecular desorption, which creates a local carrier density gradient in the graphene channel. This result is consistent with the laser-induced variations in the electronic transport properties. The method employed in this study enables visualization of local molecular adsorption-detional optical techniques, which are limited by the diffraction limit of light.
We applied a momentum-selected photoelectron emission microscopy (PEEM) approach to image crystallographic domains in metallic thin films, even in the absence of chemical or work-function contrast. The method was employed to epitaxial Ir(111) films (similar to 60 nm) grown on sapphire(0001) by molecular beam epitaxy (MBE) using a two-step temperature protocol followed by hydrogen annealing, which yielded high crystalline quality. X-ray diffraction confirmed the (111) orientation and the presence of twinning, and rocking-curve analysis revealed a sharp component with a full width at half maximum of 0.06 degrees, reflecting high near-surface crystallinity. Atomic force microscopy showed a low surface roughness of similar to 0.3 nm. Local momentum-resolved photoelectron spectroscopy using the photoelectron momentum microscope with a 5-mu m field of view revealed large crystal domains with a single crystallographic orientation, extending over area of several hundred mu m(2). In addition, crystallographic symmetry yields mirror-symmetric momentum patterns for twin domains. Placing a contrast aperture at a selected point in momentum space and then switching to PEEM mode, we obtained complementary real-space images that resolve twin domains and their similar to 120 degrees linear boundaries-features that have been difficult to resolve with conventional PEEM owing to the negligible work-function contrast. Our results demonstrate that MBE-grown Ir(111) thin films exhibit high quality, approaching that of bulk Ir, and that we have established a growth method to achieve such films. Furthermore, the momentum-selected PEEM we used in this work provides a straightforward route to correlate reciprocal-space symmetry with real-space mapping of twin-domain structures in face-centered cubic metals.
Liquid-crystalline (LC) nitroxide radicals (NRs) with spin 1/2, localized in each mesogen core, exhibit anisotropic paramagnetic susceptibility in their LC phases. It is unclear whether the macroscopic magnetic structures of LC materials depend on the molecular orientational structures in the LC phases. Here, we report the persistence diagram of the macroscopic magnetic structures of an LC-NR on a ferromagnetic iron film in an image taken using photoemission electron microscopy. Furthermore, we discuss the topological aspect of the magnetic structures in the LC-NR by comparing the persistence diagram with that of the molecular orientational structures in a polarized optical micrograph of the same sample.
The single-source thermal vacuum evaporation (SSTVE) approach was adopted in this study to obtain inorganic perovskite thin films. The structural, morphological, compositional, and photoluminescent properties of the obtained layers were comprehensively investigated. X-ray diffraction analysis confirmed a microcrystalline structure with predominant CsPbBr3 and Cs4PbBr6 phases. Scanning electron microscopy images revealed a uniform polycrystalline morphology with crystallite sizes suitable for optoelectronic applications. Energy-dispersive X-ray spectroscopy indicated a Cs-rich composition, which was attributed to the differences in precursor vaporization behavior. The synthesized films exhibited strong photoluminescence with a distinct emission peak corresponding to the bandgap energy, confirming their potential as photoactive layers for light-emitting diodes. The SSTVE method provides a solvent-free, scalable route for fabricating high-quality inorganic perovskite films, suitable for industrial optoelectronic device manufacturing.
In the field of materials science, aluminum nitride (AlN) materials have great application potential in key fields, such as optoelectronic devices and high-frequency electronic devices, due to their unique optoelectronic properties. However, it is difficult to obtain the parameters related to its optoelectronic properties, and traditional measurement methods have low precision and poor efficiency. This study aims to solve this problem by constructing an attention-based deep neural network model to perform parameter inversion with high precision and efficiency. An experiment was conducted by employing a dataset comprising the optoelectronic properties of AlN materials, covering different preparation processes and crystal structure states, and the results were compared with an improved physical model (Model 1), a model based on statistical learning (Model 2), and a model based on traditional neural networks (Model 3). The results show that the deep learning model with attention has a significant advantage in terms of the measurement error rate, and the error rate of the light absorption coefficient is only 3.2%, which is much lower than that of Model 1 (12.5%), Model 2 (10.8%), and Model 3 (8.6%). In terms of the measurement efficiency, when the light absorption coefficient is measured as an example, the number of effective measurements per unit time can reach 50, which is far greater than that of the other models. This study provides a new way to measure the optoelectronic parameters of AlN materials and is expected to promote the development of related industries.
