Membrane III-V integration has shown great promise for advancing silicon (Si) photonics. In this work, we present lateral p-i-n InP/InGaAs membrane photodetectors (PDs) epitaxially grown on Si in a vertical configuration that mirrors the geometry used in heterogeneous bonding. The membrane PDs are realized in a single epitaxial step via in-plane, in situ doping. The devices show sub-200 nA dark current (10 & micro;m length), a small-signal 3-dB bandwidth of 24 GHz, and clear non-return-to-zero on-off keying (NRZ-OOK) eye diagrams at 50 Gb/s, with eyes still measurable at 60 Gb/s. By reproducing the bonded vertical III-V/Si stack by epitaxy, the approach demonstrated here for PDs can also be extended to future hybrid Si-cavity device implementations, such as hybrid III-V/Si lasers, within a monolithic epitaxial III-V/Si platform.

Dimethyl ether steam reforming (SRD) is a promising route for efficient, on-demand hydrogen generation. In2O3-ZrO2 has proven to be a promising catalyst, when physically mixed with γ-Al2O3 yet its activity relies strongly on the nature and density of oxide-oxide heterointerfaces. Here, we use single- and double-flame spray pyrolysis (S-FSP, DFSP) to tune the hetero-contacts of In2O3-ZrO2 catalysts. Across indium loadings (1-15 wt%), D-FSP consistently outperforms S-FSP, particularly at low reaction temperatures (325-350 °C) relevant for energy-efficient H2 release. The distinct precursor mixing conditions in S-FSP and D-FSP lead to markedly different catalyst architectures, which in turn govern their catalytic performance. While S-FSP predominantly yields solid-solution-type materials with pronounced indium surface enrichment at higher loadings, D-FSP intrinsically promotes the formation of well-defined In2O3-ZrO2 hetero-contacts with a high density of interfacial sites. These interfacial sites enable more efficient conversion of the intermediate methanol in D-FSP catalysts, explaining their superior low-temperature activity and distinct CO2 & H2 selectivity. Overall, our results show that a simple variation of the flame configuration in FSP effectively controls heterocontacts and catalytic pathways, enabling efficient and durable catalysts for hydrogen generation within a circular DMEto-H2 energy storage cycle.

Photonic crystal lasers can be used to achieve high emission powers with exceptional beam quality. Vortex beams carrying orbital angular momentum have found applications in areas such as free space communication, optical trapping, and microscopy. In this paper, the growth and operation of an epitaxially grown InGaAs nanowire photonic crystal laser on silicon on insulator, emitting a vortex beam, are investigated. The device is composed of a honeycomb array of nanowires, with compressed and expanded configurations to make use of the band inversion phenomenon. The resulting bound-state-in-the-continuum modes are characterized using simulations and confirmed by measurement.

Integration of III-V membranes on silicon-on-insulator (SOI) substrates offers a promising route to provide on-chip gain for dense silicon (Si) photonics. Here, we present a materials study of InP membranes with embedded InGaAs multi-quantum wells (MQWs) directly grown above the Si waveguide layer via a tunnel epitaxy process. Cross-sectional scanning transmission electron microscopy, combining differential phase contrast imaging, energy-dispersive x-ray spectroscopy (EDX), and atomic-column-based strain analysis, confirms high-quality laterally grown InP membranes with defects confined to the V-groove region and elucidates facet-dependent MQW formation on (111)A, (110), and (111)B facets. Both EDX and strain analysis consistently reveal high-In, highly compressively strained (110) QWs (>80% In), and no misfit dislocations are observed at InP/InGaAs interfaces. In addition, under identical precursor ratios, ultra-thin QWs incorporate a higher indium composition than a thick bulk InGaAs region. These results provide practical guidance for designing efficient active regions in future electrically injected, Si-waveguide-coupled InP membrane lasers on SOI.

In this publication, we study the influence of strain and alloying on the mean inner potential (MIP) using density functional theory (DFT) within an augmented plane waves plus local orbitals (APW+LO) basis set. Two major effects have been identified allowing to model the influence of strain and alloying on the mean inner potential with a reasonable accuracy. First, alloying for constant volume results in a linear relationship between the MIP and the concentration. Second, the MIP scales with changes in volume as we already pointed out in an earlier publication [Appl. Phys. Lett. 85, 4938-4940 (2004)]. Specifically, a linear relationship between MIP and concentration x was found for AlxGa1-xAs (nearly no change in lattice parameter), whereas InxGa1-xP and GexSi1-x (volume changes with concentration x) exhibits a clear bowing. The bowing can be modelled by taking the rescaling of the MIP with the varying volume additionally into account. The rescaling could be also used to model the dependence of the MIP on strained binary cells and the density dependence of e.g. amorphous materials.

Emerging reactive spray technologies, adapted from well-established gas-phase metal oxide synthesis, provide a powerful and scalable route for producing non-oxide nanoparticles. The high surface area ternary metal sulfides are particularly attractive due to their relevance in photocatalysis, energy storage, and gas sensing. Enclosed flame spray pyrolysis (EFSP) enabled the synthesis of ternary metal sulfides AgInS2 and AgBiS2 by precisely tuning O2, fuel, and N2 co-flow and metal/sulfur (M/S) ratio to form reducing, sulfur-rich flames. Such flames suppressed oxide formation and promoted rapid nucleation of phase-pure uniform nanoparticles via combustion of high-enthalpy precursor-solvent combinations. Structural and compositional analyses using confirmed high crystallinity, consistent lattice distances, crystal structure, and homogeneous elemental distributions, with average particle sizes of similar to 11 nm for AgInS2 and nearly double for AgBiS2. A methodology was developed for dispersing the particles in aqueous solution using CTAC surfactant. Dynamic light scattering data demonstrated colloidal dispersions (hydrodynamic size 150 (+/- 4) nm) with positively charged colloids (zeta-potentials (ZP) +15 to +40 mV, hydrodynamic size 150 (+/- 4) nm) according to electrophoretic measurements. UV-vis spectroscopy revealed direct band gaps of 1.45 eV for AgInS2 and 1.50 eV for AgBiS2. These results pave the way for applications of mixed-metal sulfide nanoparticles in colloidal solutions.

Abstract Both homogeneous and inhomogeneous alloying significantly extend the spectrum of available materials and properties. In this study, (Mo,W)S2 monolayer alloys in the full composition range were grown by a modified atomic layer deposition process. The mixture of Mo and W in the crystal lattice can be controlled by the pulsed precursor schema and either a homogeneous distribution or nanostructures such as line structures and elongated islands were realized. The distribution of metal atoms is visualized by transmission electron microscopy. Raman spectroscopy is used to determine the composition x in Mo x W1−x S2 by the shift of the $${{\rm{A}}}_{1}^{{\prime} }$$ A 1 ′ mode. The optical properties are analyzed by photoluminescence spectroscopy, resulting in the determination of bowing parameters for the A and B excitonic emission. Deviations from the expected bowing are explained by a change of the energy landscape due to the presence of nanostructures. Besides the composition control, this sub-atomic layer deposition approach could pave the way to the intended formation of quantum dot and wire structures in 2D transition metal dichalcogenide heterostructures.

The pursuit of accurate, reproducible and non-invasive methods for measuring temperature in a wide range and in harsh environments for, e.g. space applications, is an enduring challenge. Luminescent thermometers have the potential of meeting these requirements, but care must be taken in choosing the appropriate materials and designs, in making a reliable and accurate calibration, and in testing their performance under different conditions.

Hydrogen offers a high-energy, carbon-free fuel alternative; however, conventional flame-based hydrogen combustion poses challenges, including NOx emissions and the risk of flame flashback. Catalytic combustion provides a safer, low-temperature approach to hydrogen utilization, but realizing it within compact, integrated systems have remained a significant challenge. This study introduces an innovative approach to hydrogen catalytic combustion by directly integrating noble metal single quantum-crystallites of Pt and Ru within a porous silica aerogel matrix embedded in a silicon chip. This configuration enables deep nanoparticle (np) penetration throughout the aerogel network, maximizing the catalytic surface area and providing efficient on-chip hydrogen combustion. The np@aerogel systems are systematically synthesized and incorporated within silicon chips equipped with a polyimide membrane and Pt thermal structures. This unique setup allows for direct, real-time characterization of hydrogen catalytic combustion by measuring resistance changes in an embedded thermistor. The Pt@SiO₂ system demonstrates a rapid and substantial temperature increase of up to 40 K upon hydrogen exposure, independent of both preheating and Pt concentration, underscoring its robustness and adaptability for micro-scale hydrogen combustion. This on-chip integration of np@aerogel catalysts marks a significant advancement for hydrogen-based energy applications, offering a compact, scalable platform for efficient catalytic combustion. This approach opens pathways for applications in thermoelectric generators and other micro-reactor technologies where controlled, localized energy generation is critical.

"Giant" magnetofossils were first discovered in pelagic Paleogene-Eocene Thermal Maximum event sections, but have also been recently identified in Late Pleistocene hemipelagic sediments such as the Bay of Bengal (BoB). Their obvious time-transgressive existence raises questions on the modern niches and habitat conditions of their still unknown producers. Here we report the occurrence of giant magnetofossils in Holocene surface sediments of the Andaman Sea (AS). Rock magnetic analyses indicate mixed (single, vortex, and multidomain state) magnetic mineral assemblages, where a prominent central ridge in first-order reversal curve diagrams signalizes a dominant biogenic magnetite component. Transmission electron microscopy reveal coexistence of conventional (prismatic, cuboctahedral, bullet) and giant (needle, bullet) magnetofossil morphologies, composed of stoichiometric, non-oxidized magnetite as confirmed by low-temperature magnetometry, energy dispersive spectrometry and crystallography. Based on the water column conditions, magnetofossil abundance and morphologies, we make inferences on habitat and environmental factors favored by the respective iron-biomineralizing organisms. Comparative analyses of water column profiles from AS and BoB revealed that relatively low, but uniform bottom water oxygenation and persistent suboxic conditions maintained by rapid renewal of deep water through circulation accompany the biomineralization of giant magnetic particles in the AS. Our investigations of two deep sediment core sites suggest that the modern AS is an ecological niche and promising investigation area for the yet-to-be-discovered, putative eukaryotic organisms, that biomineralize and release giant needle- and bullet-shaped magnetosomes to the sediment.

The use of Ru(0001) films as substrates on α-Al2O3(0001) substrates for radio-frequency magnetron sputter deposition of gallium oxide (Ga2O3) thin films is investigated regarding its dependence on the Ru film roughness; gallium oxide deposition temperature, which ranges from room temperature (RT) to 600 °C; and post-annealing up to 900 °C. The films have been characterized using various techniques. Raman spectroscopy confirms the deposition of β-Ga2O3 at deposition temperatures above 200 °C. The surface morphology was studied by atomic force microscopy (AFM), revealing that the roughness of the Ga2O3 surface strongly depends on deposition temperature, with a maximum at intermediate temperatures and a significant decrease between 400 and 600 °C. This can be explained by enhanced surface diffusion at higher temperatures. X-ray diffraction reveals poor crystallinity of all as-deposited films. Upon post-annealing, only those RT-deposited Ga2O3 films substantially gained crystallinity, which were deposited on the rougher Ru films. The cross-sectional scanning transmission electron microscopy provides insights into the grain structure, clearly disclosing the poly-crystallinity of the post-annealed Ga2O3 films with β-Ga2O3 being the predominant crystal structure. The β-Ga2O3 grain sizes are ∼10 nm for RT-deposited films and ∼40 nm for Ga2O3 deposited at 600 °C. However, γ-Ga2O3 grains of 10–20 nm in size are also found. The initial deposition of Ga2O3 on the Ru(0001) surface was studied in detail using AFM and low-energy electron diffraction (LEED). AFM shows that Ga2O3 islands nucleate predominantly at Ru step edges. LEED analysis confirms the nucleation of compressively strained epitaxial β-Ga2O3 and reveals the appearance of a (3 × 3)-reconstruction.

Annealing can improve the structural quality of transition metal dichalcogenides grown by chemical vapor deposition, atomic layer deposition, and molecular beam epitaxy. However, decomposition and desorption of chalcogens from the layers limit process parameters, such as temperature and duration. In this study, it will be shown that using confined-space annealing, realized by close contact face-to-face sample arrangement, it is possible to extend this parameter range to higher temperatures and longer annealing times. The extended temperature range leads to significantly improved optical and structural quality of MoS2 and WS2 grown by atomic layer deposition. At temperatures above 1000 °C, a rearrangement of material leads to the formation of hexagonal structures, which are not present in as-grown samples. Confined-space annealing can also be used for conversion of MoS2 layers into ternary Mo(S,Se)2 and even binary MoSe2 using a proper Se containing reservoir. The confined space allows escape of organic precursor residuals but strongly reduces outdiffusion of S, resulting in an improved confinement of S in the interspace between the samples. Hence, no additional sulfur precursor is needed for annealing, leading to a simple, low-level technology process, which is non-toxic, environment friendly, and resource-efficient.

Additive manufacturing of bulk metallic glasses using laser powder bed fusion is a challenging task, even for materials with a high glass-forming ability. This is due to the complex thermal history of the additively manufactured glass-forming materials, which are repeatedly heated upon laser processing of subsequent layers, leading to their devitrification. In this study, the influence of laser processing on the commercial Cu-based metallic glass AMLOY-CU01, having a reduced glass transition temperature T-rg similar to 0.44, has been systematically explored, incorporating high-energy synchrotron X-ray diffraction studies complemented by transmission electron microscopy. Despite the low T-rg, both vitrified and devitrified states can be obtained. The findings reveal that phase composition is weakly correlated with porosity in the keyhole regime but shows a strong correlation in the lack of fusion regime. The stabilization of the nearly glassy state of the metallic glass is achieved within a laser energy density range of 11 J mm(-3) <= e <= 25 J mm(-3) and a normalized enthalpy range of 92 <= Delta H <= 239, correlating with moderate porosity values in the obtained samples. The current results provide insights into the fundamental understanding of phase formation in glass-forming materials synthesized by laser processing and pave the way for their engineering application.

The synthesis of Cu,.oS, ZnS, and Cu,.oS-ZnS composite nanoparticles is achieved via reactive spray combustion, wherein rapid vaporization of thiophene initiates micro-explosions that promote high-temperature vapor-phase reactions under reducing conditions. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analyses reveal that the synthesized nanoparticles consist of agglomerated spherical primary crystallites, with average sizes of 12.2 nm for Cu,.oS, 10 nm for ZnS, and 10.8 nm for the Cu,.oS-ZnS composite. Elemental analysis via energy-dispersive X-ray spectroscopy (EDX) coupled with scanning transmission electron microscopy (STEM) confirms homogeneous spatial distribution of Cu and S in Cu,.oS, elevated surface oxygen content in ZnS attributed to physisorption, and substantial Cu incorporation into the ZnS lattice within the Cu,. oS-ZnS composite system. Structural analysis indicates that the contrast features observed in Cu,.oS, ZnS, and Cu-Zn mixed sulfides are consistent with their respective crystallographic symmetries, where sulfur atoms adopt well-ordered lattice positions, while copper exhibits partial site occupancy and electron density disorder attributed to the comparable ionic radii of Cu2+ and Zn2+ ions. This study underscores the efficacy of oxygen-deficient, reducing flame environments in facilitating the synthesis of binary and mixed-metal sulfide nano-materials, enabling the formation of metastable phases providing a scalable, cost-effective route for producing advanced functional materials with broad application potential.

In this publication, we study strain in kappa-(In Ga-x(1-x))(2)O-3/kappa-Ga2O3/Al2O3 heterostructures grown by plasma-assisted molecular beam epitaxy using a combination of density functional theory (DFT), x-ray diffraction (XRD), nanobeam electron diffraction (NBED), and energy-dispersive x-ray spectroscopy (EDX) for layers with low (2%) and high (18%) In concentration. Lattice parameters and elastic moduli were computed using the density functional theory formalism. The strain between kappa-(In Ga-x(1-x))(2)O-3 and kappa-Ga2O3 as well as Al2O3 and kappa-Ga2O3 was measured in two different zone axes by NBED. Due to the quasi-hexagonality of the kappa-phase, this yields an approximation for the full strain tensor. The obtained NBED results are supported by reciprocal space maps from XRD measurements. The relaxation of the layers was analyzed by comparing the measured strain data with those computed from the DFT lattice parameters and elastic moduli using the element concentrations measured by EDX, thus allowing for direct validation of the theoretical calculations by experimental data. This analysis results in satisfactory agreement and reveals that the layer with a low In concentration is fully strained (measured epsilon(zz) = 0.0037, computed epsilon(zz) = 0.0039), whereas the layer with high In concentration is fully relaxed (measured epsilon(zz) = 0.0222, computed epsilon(zz) = 0.0219). NBED, XRD, and theoretical predictions agree within their respective error margins for the strain between kappa-(InxGa1-x)(2)O-3 and kappa-Ga2O3. Overall, the absolute value of the strain between kappa-Ga2O3 and Al2O3 was measured to be smaller by NBED (measured epsilon(zz) = -0.0628) and XRD than it was computed from literature lattice parameters (epsilon(zz) = -0.0716). (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC) license (https://creativecommons.org/licenses/by-nc/4.0/)

Gadolinium (Gd) is a promising optically active lanthanide for UV emission. In this work, the optical emission properties of Gd-implanted monoclinic gallium oxide (beta-Ga2O3) thin films are investigated. Second phase formation (gamma-Ga2O3) is observed due to implantation-induced damage of the beta-Ga2O3 lattice. Annealing the implanted films results in various beta-Ga2O3 grain orientations. The relationship between the crystalline nature and the optical properties of the beta-Ga2O3:Gd3+ films is studied. Optical activation occurs after annealing 700 degrees C, revealing a photoluminescence (PL) band at 3.92 eV. This emission is attributed to the 6P7/2 , 8S7/2 transition of Gd3+ in beta-Ga2O3. Its four constituent emission components at 3.9118 eV, 3.9153 eV, 3.9221 eV and 3.9348 eV, due to the ion's 6P7/2 Stark splitting in the beta-Ga2O3 crystal field, are investigated. The transition energies are independent of annealing temperature and film growth method, highlighting the insensitivity the 4f7orbital to minor changes in the monoclinic crystal environment.

Luminescence Thermometry Atomic layer deposition (ALD) is a powerful technique for achieving smooth and robust distributed Bragg reflector (DBR) coatings on microwire ends. In article number 2400881, Manuel Alonso-Orts and co-workers create optical microcavities with ALD-coated, chromium-doped gallium oxide (Ga2O3:Cr) microwires and demonstrate their use for wide-range temperature sensors with high stability, precision and accuracy, monitoring the temperature-induced spectral shifts of the resonant peaks.

Nanoporous gold (npAu) has garnered significant attention as a highly active and selective oxidation catalyst, particularly at low temperatures. While most studies have focused on npAu derived from AuAg alloys, the incorporation of other less noble metals (LNMs), such as Cu, was shown to be a viable opportunity for tuning and enhancing its catalytic properties. The interplay between multiple LNMs present at the same time remains underexplored though. While trimetallic systems like npAu(CuAg) offer the chance for broadening the catalytic scope of npAu even further, a key challenge in utilizing them lies in understanding whether synergistic interactions or a combination of effects exerted by the individual LNMs determine their catalytic performance. To address this, we developed a reliable and reproducible method for synthesizing npAu(CuAg) and compared the trimetallic catalysts to their bimetallic counterparts npAu(Ag) and npAu(Cu) with respect to their catalytic activity for aerobic CO oxidation. Using controlled dealloying, we synthesized npAu(CuAg) with ∼20 nm ligaments, exhibiting an Ag‐rich surface, and a Cu‐enriched bulk. These trimetallic catalysts showed high conversion over a broad temperature regime ranging from room temerature to 250 °C. Electron microscopy and X‐ray photoelectron spectroscopy revealed that during activation under reaction conditions Cu segregates to the surface at elevated temperatures so that finally Ag as well as Cu sites are available enabling the activation of oxygen – on the former at low temperatures and on the latter in the high temperature region >120 °C. In this way, an overall temperature window for catalytic activity is achieved which encompasses the range of npAu(Ag) as well as that of npAu(Cu). At the same time, the thermal stability of the nanoporous network is improved, demonstrating in essence that the ternary alloy outperforms the binary systems by unifying catalytically relevant features of both LNMs.

The objective of this study is to investigate the influence of various process parameters, such as the fuel-to-oxygen ratio, precursor flow rate, co-flow rate, and different metal-to-sulfur ratios on the properties of metal sulfide particles synthesized via flame spray pyrolysis (FSP). The particle size increases with increasing dispersion oxygen flow and copper sulfide is obtained only when the fuel-to-oxygen ratio is equal to or higher than 1.5. The temperature of the flame rises with an increasing precursor flow rate and copper sulfide is formed at a precursor flow rate of 5 mL min-1 or lower, while contamination occurs above 5 mL min-1. A Co-flow rate above 100 L min-1 is required to cool the aerosol stream before deposition on the filter. A pure copper sulfide phase is produced when sulfur is more than 5 times in molar ratio compared to Cu in the liquid solution and particle size decreases with increasing sulfur concentration. This research will contribute to a better understanding of the fundamental formation process of metal sulfides under oxygen-lean gas-phase conditions and serve as a milestone in optimizing synthesis parameters for various applications.