Browse Articles

Correction: Intraspecific drought tolerance in Ugandan Coffea canephora for accelerated breeding selection

Pressure-induced contact resistance dominance in scanning spreading resistance microscopy of undoped InAs/GaSb heterostructure

This study examines the nature of current contrast formation and local transport mechanisms during scanning spreading resistance microscopy (SSRM) investigation of an undoped InAs/GaSb heterostructure. We demonstrate that in the high contact force regime (>100 nN), which is essential for stable visualization of layers on the cleaved cross section of the structure, an anomalous current signal distribution emerges. The current from GaSb layers significantly exceeds that from InAs layers. Based on a combination of SSRM data with numerical modeling of the carrier distribution within the layers, we demonstrate that the observed contrast is predominantly determined by contact resistance (Rc) rather than spreading resistance (Rs). This phenomenon is interpreted within a model in which the high local pressure at the nanocontact induces a compressively strained shell. This highly deformed region generates a high, steep potential barrier that suppresses interband electron tunneling at the diamond tip–InAs interface. Conversely, the GaSb valence band structure preserves a quasi-metallic hole transport path. Our results indicate the decisive role of tip-induced band structure modification during the nanoscale electrical characterization of narrow-gap materials.

The forms and purpose of work undertaken by family carers of people living in a care home with a cognitive impairment across a care trajectory

When older people move into care homes, family carers continue to provide unpaid support and care but little is known about how the types of work they undertake and how work changes over time. Drawing on data collected from semi-structured interviews with 29 family carers, we describe six forms of work carers undertook across the care trajectory. These were body work, comfort work, information work, coordination work, safety work and biography work. Whilst the nature of each form of work changed over time, carers undertook work across all phases of the care trajectory. This work was purposeful, undertaken to maintain the care recipient’s dignity, health, wellbeing and functional and cognitive abilities.

Radiation-resistant InGaAs nanoscale air channel photodiodes

The nanoscale air channel photodiode (NACPD) is an emerging device that combines the advantages of vacuum phototubes and semiconductor photodiodes. Its ballistic transport mechanism theoretically enables high-speed operation and high radiation hardness. However, the irradiation performance of NACPDs has not yet been fully investigated. This study investigates the effects of gamma and neutron irradiation on the performance of InGaAs NACPDs. Experimental results show that gamma irradiation has a more pronounced impact on the dark current than neutron irradiation. After exposure to 100 krad(Si) gamma radiation at a dose rate of 10 rad(Si)/s, the dark current increased by approximately 40%. In contrast, the dark current remains largely unchanged following 1.2 MeV neutron irradiation up to a fluence of 5 × 1011 n/cm2. Both gamma and neutron irradiations have minimal influence on the photocurrent, with variations remaining below 10%, and devices exhibited stable performance before and after irradiation. These findings indicate that InGaAs NACPDs possess exceptional radiation tolerance, making them promising for photodetection and sensing applications in space missions and nuclear power environments.

Effects of vascular endothelial growth factor-A and -C on wound healing in wild-type mice

This study aimed to investigate whether periwound subcutaneous administration of vascular endothelial growth factor-A (VEGF-A), VEGF-C, or both promotes wound healing in wild-type (WT) mice. A total of 40 9-week-old male BALB/c mice were used in this study. Two circular full-thickness skin wounds were created. Mice were treated with VEGF-A on day 4 after wound creation (VEGF-A group), VEGF-C on day 7 after wound creation (VEGF-C group), or VEGF-A and VEGF-C (VEGF-A + C group). The control group received subcutaneous saline injections on days 4 and 7. Photographs were taken, the wound area was measured, and the covering materials were changed for 15 days. Lymphography was performed before wound harvest. Tissues were harvested 4, 7, 10, and 14 days after wound creation and stained for lymphatic and blood vessels. The wounds in each group healed almost identically. No significant differences were observed between the VEGF-A, VEGF-C, and VEGF-A + C groups and the control group throughout the observation period. Similarly, no significant difference in the number of lymphatic and blood vessels within the granulation tissue after wound creation was observed between the VEGF-A, VEGF-C, and VEGF-A + C groups and the control group. Collecting lymphatic vessels did not regenerate across the wound, whereas capillary lymphatic vessels regenerated within the wound. Endogenous repair responses in acute wounds in WT mice progress relatively rapidly, and angiogenesis and lymphangiogenesis are sufficiently induced without VEGF-A or VEGF-C. Therefore, additional exogenous VEGF-A or VEGF-C may provide little incremental benefit, consistent with a ceiling effect.

Hyperspectral single-pixel imaging from visible to short-wave infrared

Hyperspectral imaging enables simultaneous acquisition of spatial and spectral information and plays a key role in material identification and compositional analysis. However, existing camera-based hyperspectral imaging systems are constrained by detector materials and spectral acquisition schemes, making it challenging to achieve broadband coverage and high spectral resolution. This limitation restricts their application in scenarios requiring high spectral accuracy and broadband spectral analysis. In this work, we propose a hyperspectral single-pixel imaging approach that realizes high spatial and spectral resolution imaging from 371 to 1725 nm. The proposed method takes advantage of the complementary angular reflection states of a digital micromirror device to partition the modulated visible and short-wave infrared light into two physically separated optical channels, each coupled to an independent spectral detection module. The system achieves spectral resolutions of 1.1 nm in the visible band and 3.3 nm in the short-wave infrared band and reconstructs a 128 × 128 × 770 hyperspectral data cube. Moreover, acceptable reconstruction is achieved at sampling ratios as low as 10% using compressive sensing. Imaging experiments on various samples validate the performance of the system and demonstrate its potential for industrial inspection and biomedical analysis.

Performance enhancement in MoS2/CuInP2S6 photodetectors via topography-designed flexoelectric fields

Flexoelectricity, driven by strain gradients, offers a mechanical route to manipulate ferroelectric polarization and electronic states for nanoscale applications. In this work, we demonstrate topography-induced flexoelectric engineering to modulate the energy band structure of the MoS2/CuInP2S6 (CIPS) heterostructure for high-performance optoelectronics. By deforming CIPS flakes over designed topographical variations, controlled strain gradients can be induced to pin the ferroelectric polarization via a flexoelectric potential field. This locally defined polarization serves as an effective modulation for the MoS2 band structure. By utilizing a nanowire to induce local curvature, a potential barrier is created in the MoS2 channel without requiring doping or electrostatic gating, which suppresses thermally excited carriers while simultaneously promoting the separation of photogenerated carriers. The curved MoS2/CIPS photodetector exhibits a significant performance enhancement. Under 450 nm illumination, the responsivity increases from 0.93 to 4.74 A/W, and the specific detectivity reaches 2.22 × 1012 Jones, a tenfold enhancement over regular devices. These results establish a direct link between topography-controlled flexoelectric modulation and device functionality, providing a versatile route for designing energy landscapes for 2D devices.

Barrier–channel intermixing and 2-dimensional electron gas degradation in Al-rich Al(Ga)N/AlGaN high electron mobility transistor heterostructures

In this work, we report on recent results in understanding and addressing the issue of interface smearing in high-aluminum content AlGaN/AlGaN heterostructures. On the one hand, the growth of high-crystal quality AlGaN by metal–organic vapor phase epitaxy requires the use of high temperatures, but, on the other hand, this may lead to alloy intermixing between barrier and channel layers, which smoothens out the polarization contrast and severely degrades or even completely destroys the 2-dimensional electron gas (2DEG). We show that x-ray diffraction analysis can be used as a nondestructive way to assess the sharpness of the interface, and that improved growth schemes can be successfully used to achieve high-quality 2DEG, as confirmed by contactless resistivity measurements. In particular, sheet resistivities around 2500 Ω/□ were demonstrated for AlN/Al0.75Ga0.25N, consistent with the best-reported values in the literature.

Ultra-wide Love-mode bandgaps in high-frequency thin-film surface acoustic wave phononic crystals on LiTaO3/SiC

Thin-film surface acoustic wave (TF-SAW) phononic crystals (PnCs) are promising for manipulating gigahertz acoustic waves, but achieving wide bandgaps at high frequencies remains challenging because achieving them requires both strong acoustic confinement and efficient periodic modulation. Here, we demonstrate high-frequency TF-SAW PnCs on a LiTaO3/SiC platform and realize ultra-wide Love-mode bandgaps in the gigahertz regime. Using a 200-nm-thick 42°YX-cut LiTaO3 thin film on SiC, we systematically investigate two representative geometries: a two-dimensional triangular lattice of etched air holes and a one-dimensional groove array. Transmission-line measurements confirm pronounced suppression of Love-mode propagation over 2.64–3.31 GHz (22.5%) for the triangular-lattice PnC and 2.50–3.29 GHz (27.3%) for the 1D groove PnC, in agreement with the calculated band structures. We further clarify the geometric design trends governing the bandgap characteristics and identify deeper etching together with reduced lattice period as practical routes toward even wider bandgaps and higher operating frequencies. These results establish LiTaO3/SiC TF-SAW PnCs as a compelling platform for high-frequency, wideband acoustic wave manipulation and highlight their strong potential for next-generation integrated acoustic devices, including filters, resonators, and sensors.

Scattering mechanism of 2DEG in ScAlN/GaN heterostructures grown by plasma-assisted molecular beam epitaxy

We investigated the transport properties of 2DEG in ScAlN/GaN heterostructures prepared by plasma-assisted molecular beam epitaxy. Four samples with Sc compositions of 3%–17% and ScAlN barrier thickness of 4–6.6 nm were grown on GaN/SiC template substrates. In situ reflection high energy electron diffraction patterns and atomic force microscopy images confirmed the atomically smooth surface. The atomic-resolution scanning transmission electron microscopy image demonstrated an abrupt ScAlN/GaN interface. At room temperature, the sample exhibited a sheet electron density of 2.0–3.1 × 1013 cm−2 and an electron mobility of 179–468 cm2/Vs. The sheet electron density remained nearly constant across temperatures from 2 to 400 K, indicating that the 2DEG is induced solely by the polarization effect. As the temperature decreased, the mobility increased and eventually saturated. The scattering mechanisms limiting electron mobility were analyzed, accounting for the increased effective mass due to the non-parabolicity of the conduction band at a high sheet electron density. The calculated total mobility shows excellent agreement with the experimental data, suggesting that temperature-independent interface roughness scattering is the dominant mechanism. These findings provide critical insights for understanding and improving the transport properties of 2DEG in ScAlN/GaN for HEMT applications.

Anomalous spatial response of transverse thermoelectric thin-film devices under localized thermal excitation

Localized thermal excitation is ubiquitous in practical heat-flux sensing but deviates from the uniform-heating assumption underlying conventional transverse thermoelectric (TTE) models. Here, we demonstrate that TTE thin-film devices exhibit an intrinsic spatial response under point-like heating, where the output voltage depends strongly on the excitation position. Finite-element simulations reveal that the cross-plane temperature difference remains nearly invariant, while the in-plane temperature gradient varies significantly with heating location. This lateral gradient introduces an additional thermoelectric contribution that can enhance, suppress, or even reverse the output signal. The same spatial-dependence mechanism is further reproduced in finite-element simulations of Cu-Constantan multilayer devices, showing consistent behavior without polarity reversal. These results establish that the TTE response arises from the coupling of cross-plane and lateral thermal gradients, extending the conventional ΔTz-dominated interpretation to localized-heating conditions and providing a physical basis for position-dependent calibration and spatial-error assessment in localized heat-flux sensing.

Significant red-emission enhancement using column-top-exposed InGaN-based nanocolumn plasmonic crystals with honeycomb lattice

Red emission remains a major bottleneck for practical full-color micro-light-emitting diodes (microLEDs) because the quantum efficiencies of InGaN decrease in the long-wavelength region. To enhance red emission, this study developed a honeycomb-latticed InGaN/GaN nanocolumn array integrated with an Ag-based plasmonic LED structure. Finite-difference time-domain simulations were used to optimize the lattice parameters, identifying a = 220 nm and D = 190 nm as the optimal geometries. This design provided an electric-field enhancement of approximately 4.5 at λ = 623 nm, indicating strong surface plasmon polariton coupling in the red region. A device fabricated with the same parameters exhibited up to a 6.3-fold photoluminescence enhancement under surface excitation, outperforming the 5.9-fold enhancement previously achieved under backside excitation. These results demonstrate that honeycomb-latticed plasmonic engineering is effective for boosting red emission in InGaN-based structures and offers a promising route to high-efficiency red microLEDs.

Memory and logic operations in self-powered multiferroic photodetectors

The in-sensor computing paradigm, which enables rapid signal processing with low energy consumption, pursues a frontier model to reduce data transmission and redundancy. The direct conversion of light signals into photocurrent is achieved in multiferroic photodetectors, which implement in-sensor computing. The millisecond response and detectivity of ∼1015 Jones enable pronounced performance in wavelengths 300–430 nm. By leveraging the plastic photocurrent/photoconductance, Bi4Ti3−xFexO12 multiferroic photodetectors exhibit memory/forgetting and logic functions (OR, AND, and NOT) under light and electric pulse stimulation, which is attributed to the coupling of magnetic photocurrent with the imprinting effect. The observations highlight the advantages of in-sensor memory and computing.

Experimental observation of photonic Landau levels induced by synthetic magnetic fields

Pseudo-magnetic fields, as artificially synthesized gauge fields, have been a subject of significant research attention in classical wave systems. In this study, the pseudo-magnetic field control is realized through bidirectional parameter modulation applied to a two-dimensional photonic crystal. By lowering the symmetry of the photonic crystal, the shift of Dirac cones is induced, thereby forming quantized photonic Landau levels. Experimental observation of quantum Hall-like edge states between Landau levels enables controllable unidirectional transport of electromagnetic waves along both x and y directions. By designing opposite pseudo-magnetic fields within the photonic systems, we can achieve the snake-like interface state. Our research has expanded the physical properties of the pseudo-magnetic field and provided a new approach to its potential applications in electromagnetic wave control.

Combined modulation of electrical and thermal transport properties in diamond (100) surfaces via reconstruction and passivation

The intrinsic metallicity of diamond (100) surfaces, arising from unsaturated dangling bonds, remains a critical bottleneck for their integration into high-performance electronic devices. Here, we conduct a systematic first-principles investigation into the modulation of electronic and thermal properties via surface reconstruction and chemical passivation, complemented by homogeneous nonequilibrium molecular dynamics simulations. Our results demonstrate that surface reconstruction via dangling-bond saturation drives a transition from metallic to semiconducting characteristics, with the 2 × 1 reconstruction exhibiting the lowest surface energy (0.294 eV/Å2) and optimal stability. Furthermore, the introduction of functional groups (–F, –H, –O, –OH, and –NH2) enables precise modulation of the band structure and work function of the diamond (100) surface. Among the investigated functional groups, the H-terminated surface stands out as the optimal configuration, achieving a high acoustic-phonon-limited hole mobility (∼2.09 × 104 cm2 V−1 s−1) while maintaining a remarkable thermal conductivity of 726.2 W m−1 K−1. Our findings provide critical theoretical guidance for the development of high-performance diamond-based power electronics and thermal management systems.

Metallic cicada wing-inspired surfaces fabricated via nanoimprint lithography coupled with pulse electrodeposition for enhanced wetting and thermal functionality

Nanostructured surfaces found in nature offer powerful strategies for thermal-fluid manipulation, yet their replication into durable engineered materials is constrained by fabrication limitations and a lack of comprehensive performance testing. We optimized a dissolvable nanoimprint lithography technique by combining it with pulse electrodeposition to create a repeatable, high-fidelity nanoscale replication method that transfers cicada wing nanopillars onto copper surfaces with >95% geometric fidelity. The resulting nanostructured metal surfaces achieved near cicada wing superhydrophobicity after silane modification and exhibit markedly enhanced pool-boiling heat transfer performance, with a 200% increase in critical heat flux compared to smooth copper samples. This work provides a versatile protocol for exploring nanoscale structure–function relationships and advancing high-efficiency cooling technologies.

Impact of low growth temperature on hole concentration in polarization-doped AlGaN on AlN

We investigated the impact of growth temperature on hole concentration in polarization-doped AlGaN with high AlN mole fraction on AlN, without Mg doping. A significantly lower growth temperature (around 800 °C) results in a higher hole concentration of 5 × 1018 cm−3 at room temperature in polarization-doped AlGaN without Mg doping, compared with traditional growth temperatures above 1000 °C. Furthermore, a hole concentration of 1 × 1018 cm−3 was observed even at 80 K in such an AlGaN layer without Mg doping, indicating that the hole concentration of 1 × 1018 cm−3 was induced by polarization doping alone. Previously, the hole concentrations in such AlGaN layers relied on a combination of polarization doping and Mg doping. Our results demonstrate that low growth temperature enables high hole concentration even without Mg doping.

Cladding based GaN waveguide engineering for efficient octave-spanning spectra generation and fceo detection

Extending the spectral content of femtosecond lasers to span at least one octave is key for their stabilization through self-referencing. An effective way to achieve this goal is to leverage soliton dynamics and dispersive wave (DW) generation in third-order nonlinear waveguides or fibers. Tuning of the DW position at the second harmonic of the pump is still a challenge, and it results in an excessive power requirement on the input pulse. Here, we show a new tuning mechanism of DW position in GaN waveguides by controlling the thickness of the cladding deposition. We demonstrate efficient octave-spanning supercontinuum generation by controlling the position of the DW and detecting the carrier-envelope offset frequency with only 22 pJ of pulse energy with, respectively, 100 kHz resolution and 100 Hz video bandwidth.

Magnetic skyrmions in two-dimensional half-metallic MoX2 (X = S, Se)

Magnetic skyrmions hosted in two-dimensional (2D) magnets offer exciting prospects for next-generation spintronic information storage and processing. Nevertheless, progress on skyrmions in 2D systems has been limited, mainly owing to the inversion symmetry of most 2D magnets, which in turn leads to the lack of the key factor Dzyaloshinskii–Moriya interaction (DMI) for generating topological magnetic structures. In this study, 2D half-metallic MoX2 (X = S, Se) monolayers are investigated by first-principles calculations and atomic spin simulations, which reveal their high Curie temperatures, strong DMI, and intrinsic chiral spin textures. Crucially, both MoS2 and MoSe2 can host stable skyrmion states over a wide range of external magnetic fields. Moreover, a dimensionless criterion is used to clarify the relationship between magnetic parameters and spin textures. The findings highlight that MoX2 monolayers are promising candidates for developing spintronic devices based on topological spin textures.

Scattering-induced loss in ferroelectric photonic devices

Ferroelectric materials have colossal optical nonlinearities, but their integration into quantum photonic chips is made challenging by the additional loss mechanisms that they introduce. Here, we present a perturbative theory that expresses non-absorptive (elastic) photon scattering-induced loss as a functional of a general spectral density for spatial fluctuations of electric permittivity. We apply the theory to calculations of attenuation coefficients α in slab waveguides in order to compare two distinct loss mechanisms: Interface roughness and ferroelectric domain disorder. Our theory can account for realistic roughness without special symmetry considerations, and it demonstrates how to use electron microscopy images of ferroelectric domains to obtain explicit numerical predictions for α. Loss is maximum when the mean domain length is comparable to the wavelength of light (Mie regime), indicating that, for telecom wavelengths, sub-micron domains (Rayleigh regime) or single domain waveguides provide equivalent strategies for reducing loss.