Zinc oxide (ZnO) is a wide-bandgap semiconductor with excellent optical and electrical properties, making it a promising material for a wide range of applications in optoelectronics and sensors. The properties of ZnO can be easily modified through doping and defect engineering, which determines its long-term stability and ultimate application. One of the most well-known dopants for ZnO is aluminum (Al), which is used to produce the transparent conductive oxide AZO. In this study, using positron annihilation spectroscopy (PAS) and photoluminescence (PL), we demonstrate defect engineering in AZO through millisecond flash-lamp annealing. We show that the nature of the defects strongly depends on the Al-concentration. The highest electrical conductivity of AZO is obtained at an Al:Zn layer ratio of 1:20, i.e., 2.64 at. % Al. Samples with higher Al content are more resistant to annealing and contain more defects. PAS results reveal the presence of zinc vacancies (VZn) and zinc–oxygen vacancy complexes (VZn+O) in the delta-AZO thin films, and although the PAS and PL results are generally consistent, slight differences suggest the possible existence of non-optically active defects that are not revealed by the PL measurements. Additionally, an appropriate amount of aluminum doping contributes to improving the crystallinity of ZnO.

Ultrafast magnetism triggered by circularly polarized radiation underpins ultrafast spin control, relevant to future technologies, e.g., opto-spintronics and magnonics. The dynamics are often complicated and intertwined among correlated subsystems, such as electrons, spins, phonons, plasmons, topology, and lattice, due to many-body quantum coupling at ultrafast timescales. Here, we demonstrate light-induced effective magnetic fields generated by selective excitation between non-equidistant Landau quantized states in graphene, a prototypical Dirac material, using circularly polarized pulses. By magnetically tuning the Landau-level transition resonance away from other low-energy excitations, we obtain a clean electrostatically controllable platform and identify the microscopic origin of the light-induced magnetic signals, independent of sublattice coupling. Because different Landau levels carry distinct optical Hall conductivities, direct modification of their occupancies via optical excitations creates transient Faraday rotation signals with dispersive magnetic-field dependence, mirroring the static magneto-optical lineshape. The induced effective magnetic field normalized by the pump electric field exceeds typical reported values for the inverse Faraday effect of electronic origin. Our results establish a clear microscopic picture of the inverse Faraday effect of electronic origin, which can trigger hierarchical dynamics among correlated sublattices once Landau-level transitions are magnetically tuned to coincide with other low-energy excitations in Dirac systems and related materials.

The interplay between electronic correlations, density wave orders, and magnetism gives rise to several fascinating phenomena. In recent years, kagome metals have emerged as an excellent platform for investigating these unique properties, which stem from their itinerant carriers arranged in a kagome lattice. Here, we show that electronic structure of the prototypical kagome metal, Fe$_3$Sn$_2$, can be tailored by manipulating the breathing distortion of its kagome lattice with external pressure. The breathing distortion is suppressed around 15 GPa and reversed at higher pressures. These changes lead to a series of Lifshitz transitions that we detect using broadband and transient optical spectroscopy. Remarkably, the strength of the electronic correlations and the tendency to carrier localization are enhanced as the kagome network becomes more regular, suggesting that breathing distortion can be a unique control parameter for the microscopic regime of the kagome metals and their electron dynamics.

Nanostructured semiconductors have unique physical properties that can have many applications, including optoelectronics, nanoelectronics, etc. Functionalization of nanoelectronic devices often requires specific electrical properties in different regions of the nanowire to form a p-n junction or ohmic contact. Such locally doped regions can be created by selective ion implantation. In the present work, we investigated the microstructure and optical properties of GaAs/GaAs:Si/AlxGa1-xAs core-shell nanowires after ion implantation and postimplantation annealing. GaAs/GaAs:Si/AlxGa1-xAs core-shell nanowires were implanted with sulfur ions at a fluence of 2.3 x 10(15) cm(-2). After ion implantation, the nanowires were subjected to flash-lamp annealing (FLA) for 3.2 ms or to conventional rapid thermal annealing (RTA) for 90 s. Raman and microstructural analyses indicate that FLA treatment with an energy density of 102 J cm(-2) can almost fully restore the original crystalline quality of the nanowires. On the other hand, photoluminescence (PL) measurements show that nanowires subjected to RTA exhibit a stronger emission intensity; however, RTA at 550 degrees C leads to severe decomposition of the AlxGa1-xAs shell.

Using infrared and Raman spectroscopies combined with high-resolution x-ray diffraction, we address several controversial aspects of altermagnetic alpha-MnTe. We show that mechanical stress applied to crystals of this material causes a drastic broadening of Bragg peaks that conceals signatures of additional phases present in the sample. Indeed, spatially resolved Raman spectroscopy reveals that the modes around 175 cm-1 often reported in alpha-MnTe are not reproducible across different positions and samples and originate from the secondary phase of MnTe2. By combining spectroscopic probes with ab initio calculations, we establish the IR-active optical phonon of alpha-MnTe around 155 cm-1 (E1u) and the Raman-active optical phonon around 100 cm-1 (E2g) at room temperature. Two intense Raman modes around 120 and 140 cm-1 are shown to be intrinsic, even though they can not be assigned to P-point optical phonons. These modes couple to magnetic order in alpha-MnTe and also to the transient reflectivity, resulting in coherent oscillations. Both sixfold rotation symmetry and inversion symmetry are preserved in bulk alpha-MnTe within our experimental resolution.

Magnetic field sensing is essential for applications in communication, environmental monitoring, and biomedical diagnostics. Quantum sensors based on solid-state spin defects, such as nitrogen-vacancy centers in diamond or boron vacancies in single-crystal hexagonal boron nitride (hBN), typically require precise alignment between the external magnetic field and the defect's spin quantization axis to achieve reliable sensing. This alignment constraint complicates device integration and hinders scalability. Here, we demonstrate room-temperature optically detected magnetic resonance (ODMR) from negatively charged boron vacancies (VB-) in commercially available hot-pressed polycrystalline hBN. The random grain orientation inherently samples a broad range of spin quantization axes, enabling alignment-free magnetic field detection. Numerical modeling further confirms that sensing remains feasible despite anisotropic sensitivity, establishing hot-pressed hBN as a robust and practical platform for quantum magnetometry. This approach paves the way toward low-cost, scalable, and mechanically stable quantum magnetic field sensors suitable for real-world deployment.

Nanostructured semiconductors have unique physical properties that can have many applications, including optoelectronics, nanoelectronics, etc. Functionalization of nanoelectronic devices often requires specific electrical properties in different regions of the nanowire to form a p‐n junction or ohmic contact. Such locally doped regions can be created by selective ion implantation. In the present work, we investigated the microstructure and optical properties of GaAs/GaAs:Si/Al x Ga 1−x As core–shell nanowires after ion implantation and postimplantation annealing. GaAs/GaAs:Si/Al x Ga 1−x As core–shell nanowires were implanted with sulfur ions at a fluence of 2.3 × 10 15 cm −2 . After ion implantation, the nanowires were subjected to flash‐lamp annealing (FLA) for 3.2 ms or to conventional rapid thermal annealing (RTA) for 90 s. Raman and microstructural analyses indicate that FLA treatment with an energy density of 102 J cm −2 can almost fully restore the original crystalline quality of the nanowires. On the other hand, photoluminescence (PL) measurements show that nanowires subjected to RTA exhibit a stronger emission intensity; however, RTA at 550°C leads to severe decomposition of the Al x Ga 1−x As shell.

The fabrication of group-IV superconducting semiconductors has received considerable attention owing to their potential for integration with hybrid semiconductor-superconductor circuits. In this context, superconducting germanium-on-insulator (GeOI) is particularly promising, as it can fully exploit the advantages of the GeOI technologies for advanced electronic devices. In this study, we demonstrate superconductivity in GeOI via Ga ion implantation and millisecond-range flash-lamp annealing (FLA). Electrical measurements showed an activated hole concentration of approximately 8 & times; 1020 cm-3, with a superconducting transition temperature of around 150 mK. Additionally, the critical magnetic field aligns well with the behavior expected for diluted superconducting semiconductors. The superconducting GeOI provides a foundational platform for potential applications in future quantum devices.

Photonic integrated circuits (PICs) are crucial for advancing optical communications, promising substantial gains in data transmission speed, bandwidth, and energy efficiency compared to conventional electronics. Telecom-wavelength photodetectors, operating near 1550 nm, are indispensable in PICs, where they enable the sensitive and low-noise conversion of optical signals to electrical signals for efficient data processing. While silicon is ideal for passive optical components, its limited absorption in the optical telecommunication range (1260-1625 nm) typically necessitates integrating an alternative material, such as germanium, for photodetection - a process that introduces significant fabrication challenges. Here, we present a high-performance, all-silicon waveguide-coupled photodetector, which operates at room temperature within the optical telecom C band. By introducing deep-level impurities into silicon at concentrations close to the solid-solubility limit, we enable efficient sub-bandgap absorption without compromising recombination carrier lifetimes and mobilities. This detector achieves a responsivity of 0.56 A/W, a quantum efficiency of 44.8

On-demand polarization control of electromagnetic waves is the fundamental element of modern optics. Its interest has recently been expanded in the terahertz (THz) range for coherent excitation of collective quasiparticles in matters, triggering a wide variety of non-trivial intriguing physics, e.g., anharmonicity, nonlinear coupling, and metastability. Wavelength tunability in THz polarization control is fundamentally important for the resonant excitation of collective modes. Here, we propose and demonstrate a simple and convenient THz phase retarder based on the Mach–Zehnder interferometer to obtain circular polarization. The efficiency of THz polarization conversion is demonstrated by the achieved high polarization degree of more than 99.9

The doping of two-dimensional (2D) transition metal dichalcogenides (TMDCs) by an approach compatible with circuit integration is crucial. However, ion implantation, the most commonly used method for doping semiconductors, poses significant challenges for 2D-TMDCs because of the requirement for ultralow ion energy and the difficulty of restoring damaged 2D materials. Here, we achieve bipolar transport in intrinsic n-type WS2 monolayers through phosphorus (P) ion implantation using commercial ion implanters. Millisecond flash lamp annealing is employed to remove ion-induced defects and activate P. Experimental results show a clear change in carrier type with increasing ion fluence. Samples implanted with a fluence of 7.5 x 10(12) cm(-2) display ambipolar transport behavior with an on/off ratio of 4.4 x 10(5) and 1.6 x 10(6) for p- and n-branch, respectively. At the same time, the optical and structural properties of WS2 are well preserved. All of these findings not only complement the fundamental understanding of 2D-TMDCs but also provide a possible route for heterointegration of TMDCs into current Si-based semiconductor technologies.

Determining the concentration of electrically active dopants in III-V core-shell nanowires has long been a challenge due to the difficulty of developing ohmic contact with the nanowire core. In this paper, we have used a noncontact optical method to estimate the electron concentration in Si-doped GaAs:Si/Al0.25Ga0.75As core-shell nanowires. The temperature-dependent photoluminescence (PL) spectra of these GaAs:Si/Al0.25Ga0.75As nanowires indicate that at 15 K, the carrier concentration in the conductive core of the core-shell nanowires can be as high as 1.40 x 1018 cm-3. The band-filling effect was considered to accurately determine the concentrations of carriers in the nanowires using optical methods. The highest electron density is achieved for a nominal Si concentration of 1.89 x 1019 cm-3, and a further increase in Si concentration reduces the effective doping level due to the amphoteric behaviour of Si in GaAs. The dependence of the integrated PL intensity on the laser power at T = 15 K exhibits a typical two-thirds power dependence, indicating the presence of a nonradiative Auger recombination mechanism in the nanowire under high carrier concentration.

We demonstrate a highly efficient method for upconverting broadband sub-terahertz (sub-THz) signals to multiple terahertz (THz) bands using a photoconductive antenna coupled with the TELBE radiation source, leveraging the unique properties of HgTe-based Dirac materials. HgTe heterostructures known for their robust third-order nonlinearities, enhance frequency mixing and signal amplification across THz bands. We achieved a field conversion efficiency over 2% for room temperature.

We investigate ultrafast electron dynamics in individual GaAs/InGaAs core-shell nanowires using near-infrared pump-mid-infrared probe nanospectroscopy based on a scattering-type scanning near-field technique. Our results reveal a distinct blue shift in plasmon resonance frequency induced by photodoping. By extracting time-dependent electron densities and scattering rates, we gain insights into the effects of chemical doping and nanowire surface states on recombination dynamics and carrier mobility. Varying the pump power over two orders of magnitude reveals carrier recombination times in the range from a few ps at high power to 100 ps at low power, dominated by bimolecular recombination. Our findings highlight the potential of time-resolved nanoscopy for contactless probing of free carrier mobility and recombination dynamics on a local scale in individual semiconductor nanostructures or nanodevices.

Two-dimensional van der Waals semiconductors feature a variety of stable Coulomb-bound electron-hole complexes, which determine the optical response of the materials and serve as primary carriers of energy and spin-valley encoded information. Importantly, transitions between different excitonic states are found in the terahertz spectral range, motivating the use of strong THz radiation for their manipulation on ultrafast timescales. In this work, we apply this technique to efficiently transfer populations within the manifold of excitonic complexes in monolayer WSe2, combining pulsed optical injection with a perturbation induced by a THz free-electron laser source. Monitoring time-resolved photoluminescence, we show conversion between different Coulomb-bound species across biexcitonic and excitonic regimes. Depending on the lattice temperature, these processes involve both short-lived bright and long-lived dark states. Combining experimental findings with theory support, we outline possible dissociation and formation pathways of charged excitons and biexcitons induced by the THz radiation. Finally, we demonstrate access to the formation dynamics of charged biexcitons under controlled conditions of thermalized populations of their constituents, avoiding complications of excess energies that otherwise occur after nonresonant optical excitation.

Group-IV superconducting semiconductors present promising opportunities on the development of scalable hybrid platforms for quantum devices. However, achieving superconducting states in semiconductors remains challenging, particularly concerning the origin of coherent coupling and the relationship between carrier concentration and critical temperature. In this study, ion implantation and flash-lamp annealing are used to achieve hyperdoped Si x Ge 1-x alloys. We investigate the tunability of the superconducting transition temperature by adjusting the Si/Ge composition and the Ga implantation fluences. As the Si concentration in Si x Ge 1-x increases, while maintaining identical doping fluences, the critical temperature is reduced from 550 mK to 40 mK. This is due to the lower solubility of Ga in Si than in Ge. Furthermore, as the Ga fluence decreases, the critical temperature is also reduced from 550 mK to 80 mK. We establish a qualitative correlation between critical temperature and free-hole concentration, which can be tuned by varying the Ga implantation fluence and the Si x Ge 1-x alloy composition.

Incorporating lead (Pb) into the germanium (Ge) lattice emerges as a promising approach for bandgap engineering, enabling luminescence at longer wavelengths and paving the way for enhanced applications in short-wave infrared (SWIR) light sources and photodetectors. In this work, we report on optical properties of GePb alloys fabricated by a complementary metal-oxide semiconductor (CMOS)-compatible process that includes Pb ion implantation followed by solid-phase epitaxial regrowth via flash-lamp annealing. Optical characterization, including photoluminescence spectroscopy and Fourier-transform infrared reflectance spectroscopy, reveals that GePb alloys exhibit a reduced bandgap compared to pure Ge, resulting in longer-wavelength emission, while also providing broadband antireflective properties below 1800 nm wavelengths due to the surface subwavelength nanostructure. These findings position nanostructured GePb as a highly promising candidate for SWIR optoelectronic applications.

The Dresden Advanced Light Infrastructure (DALI) project at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) is a visionary initiative to establish a state-of-the-art light source facility, catering to cutting-edge research in materials science, biology, and other interdisciplinary fields. A cornerstone of this ambitious project is the development of an advanced accelerator lattice tailored to meet the unique demands of high-intensity, ultra-bright photon production. This presentation introduces the conceptual framework and preliminary design of the DALI accelerator lattice. Key features include a modular design optimized for stability, flexibility, and scalability, ensuring compatibility with diverse experimental setups. The lattice must integrate advanced beam dynamics solutions to achieve precise control over beam quality, energy spread, and emittance, crucial for generating high-brightness radiation. Early design studies highlight the potential of DALI to set new benchmarks in light source performance. This presentation seeks to engage the accelerator community in refining the lattice design and exploring its applications in cutting-edge research.

We report high-harmonics in the emission spectrum of an infrared free-electron laser. For the fundamental frequency of 16.5 THz harmonics up to 28th order are detected. Interestingly, in addition to integer odd and even harmonics of nth order we observe fractional harmonics. Operation at 5.4 THz produces harmonics up to 75th order.