Control of light emission in solids underpins modern photonics, quantum technologies, and radiation detection. Strong coupling between excitons and confined electromagnetic modes forms hybrid light–matter states known as polaritons, enabling new regimes of emission control. To date, such effects have been largely restricted to nanoscale or ultrathin architectures and mostly reported under optical or electrical excitations, limiting their relevance for bulk scintillator applications. Here, macroscopic exciton–plasmon strong coupling is demonstrated in bulk nanocomposite scintillators based on lead-halide perovskite nanoplatelets coupled with silver nanocubes. Precise resonance alignment between excitonic and plasmonic modes is achieved through nanocube size engineering and temperature tuning, resulting in pronounced Rabi splitting and clear mode anticrossing. The extracted coupling strength exceeds both excitonic and plasmonic dissipation rates, confirming operation well within the strong-coupling regime. Angular-resolved photoluminescence measurements directly reveal polaritonic dispersion, providing unambiguous evidence of hybrid mode formation. Strong coupling is realized in a bulk scintillating composite, demonstrating that polaritonic hybridization can be implemented directly in materials designed for ionizing radiation detection. These results establish a scalable route to polaritonic scintillators in which light yield and temporal response can be engineered through controlled light–matter hybridization, opening opportunities for next-generation radiation detectors and medical imaging technologies.

Abstract Nickel oxide (NiO) is known as a p-type semiconductor that is increasingly used in various semiconductor devices, including GaN-based devices, but the charge transfer at the NiO/GaN heterointerface and the Fermi level position at this heterointerface have not been thoroughly studied. In this work, NiO with different electrical properties (nominally n- and p-type) was used to deposit onto GaN-cap/GaN:Si structures and fabricate NiO/GaN heterojunction diodes. The valence band discontinuity between NiO and GaN was determined using ultraviolet photoelectron spectroscopy to be ∼1.9 eV. The Fermi level position at the NiO/GaN heterojunction and carrier transfer after junction formation were investigated using contactless electroreflectance (CER). It was observed that at the nominally n-NiO/GaN heterointerface, electrons are transferred from the NiO layer to the GaN layer and the Fermi level in GaN is located near the conduction band, while at the p-NiO/GaN heterointerface, electrons from the surface states in GaN are transferred to the NiO layer and the Fermi level at the p-NiO/GaN heterointerface shifts toward the valence band and is located ∼0.84 eV below the conduction band in GaN. NiO/GaN heterojunction diodes were obtained for both nominally n-type and p-type NiO layers. The potential barrier for p-NiO/GaN heterojunction diodes reached a value of ∼1.0 eV, which corresponds to the Fermi position at the p-NiO/GaN heterointerface determined by the CER method (∼0.84 eV), and the breakdown voltage exceeds 600 V. For nominally n-NiO/GaN heterojunction diodes, the potential barrier is much lower (∼0.5 eV), and the breakdown voltage is also lower (∼400 V). This is fully understood since the NiO/GaN heterojunction is type II with a barrier for electrons in the NiO layer, and this layer is depleted due to formation of the n-NiO/GaN heterointerface in contrast to the p-NiO/GaN heterointerface.

The growth of Cr films, formed by in situ physical vapor deposition on atomically clean, n-type, GaN(0001)-(1 x 1) surfaces, has been studied using X-ray and UV photoelectron spectroscopies (XPS, UPS). Additionally, structural information was obtained from reflection high-energy electron diffraction (RHEED). The growth of Cr follows the Stranski-Krastanov mode: initially, Cr wets the (0001) surface with two complete, disordered monolayers and then begins to follow a three-dimensional growth mechanism. The Schottky barrier height was determined between Cr layers and n-GaN(0001). At elevated temperatures the chemically driven Ga diffusion from the bulk initiates intermixing of Ga and Cr. No dissolution of Cr into the GaN substrate was observed. Released nitrogen atoms partially remained on the surface. RHEED patterns reveal surface ordering induced by annealing. UPS, apart from valence band measurements, was used to determine the work function for both bare and Cr-covered GaN surfaces.

In this paper, we present results of x-ray diffraction investigations of GaN micro-pillars grown on GaN template. These rods are special in so far that they have stable a- and m-plane side walls and dodecagonal and not hexagonal shape as usual. Such growth mode is simulated by adding As as surfactant. The work shows the influence of changing the amount of gallium and arsenic and lowering the temperature on the growth of micro-pillars. Changing the growth parameters led to both a change in the density of the growing micro-pillars, their height and width, and their structural parameters, such as a disturbance in the direction of growth of the structures. In order to characterize the studied samples, measurements were carried on the configuration from the surface and from the edge of the sample. This measurements method allowed to visualize the structure in the perpendicular and parallel directions of the micro-pillars growth. In addition, the strain and mosaic analysis showed correlations between the resulting shape and density of the rods and the strain of the GaN-pillar and GaNAs crystalline lattice.

Van der Waals crystals offer opportunities to engineer material properties by stacking diverse 2D layers into heterostructures. Charge redistribution at these interfaces, governed by band alignment and Fermi levels, enables control over optical, electronic, and magnetic behavior. In this study, we investigated the band alignment and excitation spectra of exfoliated MPS3 (M = Mn, Fe, Co, Ni) using X-ray and UV photoelectron spectroscopy, optical absorption, and DFT + U calculations. Ionization potentials from 5.4 eV (FePS3) to 6.2 eV (NiPS3) were determined. The resulting band diagrams differentiate localized d states from hybridized p-d states, offering insights for designing functional heterostructures. Selective occupation of unoccupied 3d states provides a pathway to tune magnetic order. Theoretical results show that MnPS3 is well-aligned for both hydrogen and oxygen evolution reactions (HER and OER), while other MPS3 are promising for OER. MnPS3/NiPS3 heterostructure exhibits optimal band alignment for efficient water splitting across a broad pH range.

Surface engineering in GaN-based technology is essential for enhancing existing devices and exploring new opportunities, potentially turning GaN surfaces into platforms for devices incorporating two-dimensional crystals. In this article, we show the impact of arsenic termination on the electronic properties of GaN (0001)-oriented crystals. For this purpose, photoemission experiments and density functional theory (DFT) calculations were conducted. As atoms were vapour-deposited using an As-cracker source onto a clean GaN(0001) surface maintained at a temperature of 300 degrees C under ultra-high vacuum conditions. This preparation procedure allowed to obtain an As coverage of about one monolayer. The presence of As atoms on the GaN(0001) surface alters the valence-band electronic structure, with surface states positioned near the valence band maximum being evident, as confirmed by UV photoelectron spectroscopy (UPS) as well as DFT calculations. DFT was utilized to explain the origins of these features, examining various configurations of As atoms on the GaN(0001) surface.

We report magnetization changes generated by an electric field in ferromagnetic Ga1-xMnxN grown by molecular beam epitaxy. Two classes of phenomena have been revealed. First, over a wide range of magnetic fields, the magnetoelectric signal is odd in the electric field and reversible. Employing a macroscopic spin model and atomistic Landau-Lifshitz-Gilbert theory with Langevin dynamics, we demonstrate that the magnetoelectric response results from the inverse piezoelectric effect that changes the trigonal single-ion magnetocrystalline anisotropy. Second, in the metastable regime of ferromagnetic hystereses, the magnetoelectric effect becomes non-linear and irreversible in response to a time-dependent electric field, which can reorient the magnetization direction. Interestingly, our observations are similar to those reported for another dilute ferromagnetic semiconductor Crx(Bi1-ySby)1-xTe3, in which magnetization was monitored as a function of the gate electric field. Those results constitute experimental support for theories describing the effects of time-dependent perturbation upon glasses far from thermal equilibrium in terms of an enhanced effective temperature.

One of the approaches to improve p-doping properties in (Al)GaN-based materials is using a method called polarization doping. In this study, the graded p-AlGaN contact layers were deposited using plasma-assisted molecular beam epitaxy with different III/N ratios. To study the influence of Ga flux on the structural and electrical properties of the grown graded p-AlGaN structures, the samples were investigated using reflection high-energy electron diffraction, atomic force microscopy, secondary ion mass spectrometry, X-ray diffraction, and Hall effect measurements. The electronic structure of the samples was investigated by X-ray absorption near edge spectroscopy, while the polarity of the layers was analyzed by means of transmission electron microscopy. Our study reveals that growing with a higher Ga flux increases Mg incorporation and changes its distribution in the graded layer. However, it was shown that the main factor drastically affecting the magnitude and the type of conductivity in the graded p-AlGaN structures is the dislocation density. The highest hole concentration of -3.0x1018 cm-3 was observed for sample grown with a low Ga flux.

AbstractPhotoelectrolysis of water is a sustainable option for the production of hydrogen fuel. GaN nano‐ or microstructures are considered for water‐splitting due to their general high chemical stability and high surface‐to‐volume ratio enhancing the process effectiveness. In this study GaN structures with dodecagonal microrods are used as a working electrode for the water‐splitting process. Microrods are grown using a plasma‐assisted molecular beam epitaxy process allowing tailoring of microrod height and density. Their unique property is the of presence twelve sidewalls with alternating a‐ and m‐plane orientations. This enables a simultaneous study of the chemical stability of c‐, a‐, and m‐plane walls of GaN. The water‐splitting process is performed using a 1 mol l−1 NaOH electrolyte solution. Non‐zero current measured at zero bias under illumination indicates that the process takes place. A degradation of the GaN structure is observed after a prolonged process time. In short‐term exposures, etching of microrod sidewalls is observed. Roughening of the a‐plane walls studied by transmission electron microscopy indicates that this orientation is etched with a fastest rate. The internal crystalline structure is not influenced by the etching and remains stable as shown by the X‐ray absorption spectroscopy study.

Self-assembled III-nitride columnar structures hold promise for enhancing emission efficiency in the UV spectral range. The introduction of As during molecular beam epitaxial growth of GaN leads to the formation of microrods with 12 sidewalls arranged in alternating a- and m-planes. This paper investigates the growth of 12-walled columns to elucidate the nucleation mechanisms, seeding, and the role of As in growth mode switching. We uncover a dual role of As: it induces the formation of Ga droplets, serving as the initiation points for microrod growth, through its antisurfactant effect and by creating an As-containing shell over the droplets. Observation of hybrid hexagonal/dodecagonal microrods reveals the necessity of exposing microrod sidewalls to impinging As for the formation of dodecagonal columns. This is supported by the observed dodecagonal-to-hexagonal growth mode switching upon cessation of As supply during growth.

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.

The growth of GaNAs with arsenic is important due to band engineering in the valence band of GaN, but it is very challenging due to the difference in the optimal growth temperatures for GaN and GaAs. In this study, we present the results of growing GaNAs via metal-organic vapor phase epitaxy with trimethylarsine as the arsenic source. By reducing the growth temperature and increasing the V/III ratio, we obtained an As content of up to 7.6%. Crystalline material quality and composition were investigated with high-resolution X-ray diffraction. Atomic force microscopy determined surface roughness root-mean-square values between 0.4 and 2 nm. The internal structure of the layers was investigated via transmission electron microscopy, proving their high crystalline quality. It also showed that further reduction of growth temperature resulted in the formation of a zincblende GaAs polycrystalline layer.

Diluted magnetic semiconductors have attracted significant attention for their potential in spintronic applications. Particularly, magnetically doped GaN is highly attractive due to its high relevance for the CMOS industry and the possibility of developing advanced spintronic devices, which are fully compatible with the current industrial procedures. Despite this interest, there remains a need to investigate the spintronic parameters that characterize interfaces within these systems. Here, we perform spin Hall magnetoresistance (SMR) measurements to evaluate the spin transfer at a Pt/(Ga,Mn)N interface. We determine the transparency of the interface through the estimation of the real part of the spin mixing conductance, finding G(r) = 2.6 x 10(14) Omega(-1) m(-2), comparable to state-of-the-art yttrium iron garnet/Pt interfaces. Moreover, the magnetic ordering probed by SMR above the (Ga,Mn)N Curie temperature TC provides a broader temperature range for the efficient generation and detection of spin currents, relaxing the conditions for this material to be applied in spintronic devices.

The Fermi level position at the interface of a heterostructure is a critical factor for device functionality, strongly influenced by surface-related phenomena. In this study, contactless electroreflectance (CER) was utilized for the first time to investigate the built-in electric field in MXene/GaN structures with the goal of understanding the carrier transfer across the MXene/GaN interface. Five MXenes with high work functions were examined: Cr2C, Mo2C, V2C, V4C3, and Ti3C2. The physicochemical properties of the MXene/GaN structures were analyzed by using X-ray and UV photoelectron spectroscopies. It was shown that upon the coverage of the GaN surface by all investigated MXenes, a shift in the position of the surface Fermi level occurs, consequently raising the interface barrier. Additionally, the physicochemical stability of MXenes on the GaN surface was studied after annealing the structures at 750 degrees C. Our findings indicate that the annealing process increases the barrier height and the ionization energies of all studied structures. Furthermore, it has been shown that removing excess MXene material from the surface did not significantly impact the built-in electric field, emphasizing the robust physicochemical stability of the MXenes on the GaN surface. To validate the potential of engineering of MXene/GaN interface barrier, Schottky diodes with MXenes exhibiting the highest barrier height (Mo2C and V2C) were demonstrated.

One of the methods to improve p-doping properties in (Al)GaN-based materials is using a technique called polarization doping. In our study, two sets of p-AlGaN contact layers with different thicknesses of the graded layer were deposited by metalorganic vapor phase epitaxy. The grown samples were investigated by atomic force microscopy, secondary ion mass spectrometry, X-ray diffraction and Hall effect measurements to study the influence of the thickness of the graded Al0.6 -> 0Ga0.4 -> 1N:Mg layer on the structural and the electrical properties of the whole grown structure. Additionally, theoretical calculations for the contact structures with different thicknesses of the p-Al0.6 -> 0Ga0.4 -> 1N graded layer were performed. The obtained results show that the concentration of p-type carriers on the p-GaN/p-AlGaN gradient interface decreases with increasing thickness of the graded layer. Our findings reveal that among the graded structures the highest concentration of holes, 1.2 x 1018 cm-3, was obtained for a structure with 50-nm-thick graded layer, while maintaining low sample resistivity. In addition, it was also shown that non-doping of the graded layer allows to improve electrical properties.

High-resolution scanning probe microscopy (SPM) is a fundamental and efficient technology for surface characterization of modern materials at the subnanometre scale. The bottleneck of SPM is the probe and scanning tip. Materials with stable electrical, thermal, and mechanical properties for high-aspect-ratio (AR) tips are continuously being developed to improve their accuracy. Among these, GaN is emerging as a significant contender that serves as a replacement for standard Si probes. In this paper, for the first time, we present an approach that demonstrates the application of GaN microrods (MRs) as high-AR SPM probes. GaN MRs were grown using molecular beam epitaxy, transferred and mounted on a cantilever using focused electron beam-induced deposition and milled in a whisker tip using a focused ion beam in a scanning electron/ion microscope. The presence of a native oxide layer covering the GaN MR surface was confirmed by X-ray photoelectron spectroscopy. Current-voltage map measurements are also presented to indicate the elimination of the native oxide layer from the tip surface. The utility of the designed probes was tested using conductive atomic force microscopy and a 24-hour durability test in contact mode atomic force microscopy. Subsequently, the graphene stacks were imaged.

Due to the antisurfactant properties of arsenic atoms, the self-induced dodecagonal GaN microrods can be grown by molecular beam epitaxy (MBE) in Ga-rich conditions. Since temperature is a key parameter in MBE growth, the role of temperature in the growth of GaN microrods is investigated. The optimal growth temperature window for the formation of GaN microrods is observed to be between 760 and 800 °C. Lowering the temperature to 720 °C did not change the growth mechanism, but the population of irregular and amorphous microrods increased. On the other hand, increasing the growth temperature up to 880 °C interrupts the growth of GaN microrods, due to the re-evaporation of the gallium from the surface. The incorporation of As in GaN microrods is negligible, which is confirmed by X-ray diffraction and transmission electron microscopy. Moreover, the photoluminescence and cathodoluminescence characteristics typical for GaN are observed for individual GaN microrods, which additionally confirms that arsenic is not incorporated inside microrods. When the growth temperature is increased, the emission related to the band gap decreases in favor of the defect-related emission. This is typical for bulk GaN and attributed to an increase in the point defect concentration for GaN microrods grown at lower temperatures.

Here we present new findings of a comprehensive study of the fundamental physicochemical properties for GeS and GeSe in bulk form. UV and X-ray photoelectron spectroscopies (UPS/XPS) were employed for the experiments, which were carried out on in situ cleaned (100) surfaces free from contamination. This allowed to obtain reliable results, also unchanged by effects related to charging of the samples. The work functions, electron affinities and ionization energies as well as core level lines were found. The band gaps of the investigated materials were determined by photoreflectance and optical absorption methods. As a result, band energy diagrams relative to the vacuum level for GeS and GeSe were constructed. The diagrams provide information about the valence and conduction band offsets, crucial for the design of various electronic devices and semiconducting heterostructures.

Cu-based materials are used in various industries, such as electronics, power generation, and catalysis. In particular, monolayered cuprous oxide (Cu2O) has potential applications in solar cells owing to its favorable electronic and magnetic properties. Atomically thin Cu2O samples derived from bulk cuprite were characterized by high-resolution transmission electron microscopy (HRTEM). Two voltages, 80 kV and 300 kV, were explored for in situ observations of the samples. The optimum electron beam parameters (300 kV, low-current beam) were used to prevent beam damage. The growth of novel crystal structures, identified as Cu, was observed in the samples exposed to isopropanol (IPA) and high temperatures. It is proposed that the exposure of the copper (I) oxide samples to IPA and temperature causes material nucleation, whereas the consequent exposure via e-beams generated from the electron beam promotes the growth of the nanosized Cu crystals.

Growth characteristics of AlGaN layers in different conditions: pressure and ammonia flow were presented.The structures containing the AlN buffer and the AlGaN layer were grown by metalorganic vapor phase epitaxy.The goal was to find the growth conditions for AlGaN with stable 60% of aluminium and determine the aluminium concentration deviation while changing two parameters.Pressure showed bigger influence on aluminium incorporation, layer quality and surface roughness than ammonia.