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Quantum photonic networks require two distinct functionalities: bright single-photon sources and long-lived quantum memories. III–V semiconductor quantum dots (QDs) excel as deterministic and coherent photon emitters, while rare-earth ions such as erbium (Er3+) in crystalline oxides offer exceptional spin and optical coherence at telecom wavelengths. Combining these systems and their functionalities via direct epitaxy is challenging due to lattice mismatch and incompatible growth conditions. Here, we demonstrate the low-temperature pulsed laser deposition of Er3+-doped TiO2 thin films directly on GaAs and GaSb substrates. Controlled surface preparation with an arsenic cap and an oxygen-deficient buffer layer enables the growth of epitaxial anatase TiO2 (001) at ∼390 °C with sub-300 pm surface roughness, while avoiding interface degradation. In contrast, high-temperature oxide desorption or growth temperatures drive the transition to a rough, polycrystalline rutile film, as confirmed by transmission electron microscopy. Minimal coincident interface area (MCIA) modeling explains the orientation-selective growth on GaAs and GaSb. Raman and cryogenic photoluminescence excitation spectroscopy verify the crystal phase and optical activation of Er3+ ions. This multiparameter growth strategy helps preserve III–V quantum dot functionality and yields smooth surfaces suitable for low-loss nanophotonic structures. Our results establish a materials platform for monolithically integrating rare-earth quantum memories with semiconductor photon sources, paving the way toward scalable hybrid quantum photonic chips. 

Bright and high-purity single-photon sources at telecom wavelengths are essential for scalable quantum networks. Nanohole-etched GaSb/AlGaSb quantum dots (QDs) are an emerging platform for telecom-band emitters, offering freedom from strain-induced decoherence and indium-related nuclear spin noise of conventional InGaAs QDs. Here, we present a comprehensive optical spectroscopy study that reveals correlations between nanohole morphology, exciton recombination dynamics, and single-photon performance in GaSb QDs. Shallow nanoholes lead to ultrafast charge transfer that limits optical coherence, whereas deeper nanoholes yield clean neutral-exciton emission with a high bright-to-dark state branching ratio (98 ± 1%), indicating favorable conditions for efficient photon generation. Under pulsed quasi-resonant excitation, these QDs exhibit significantly enhanced single-photon purity with g(2)(0) = 0.029 ± 0.011, compared to above-band excitation (g(2)(0) = 0.18 ± 0.05). Polarization-resolved measurements across tens of QDs further reveal ultrasmall fine-structure splitting of the neutral exciton (11 ± 5 μeV), relevant for entangled-photon generation at telecom wavelengths. These results highlight the potential of GaSb QDs for high-performance quantum emitters and scalable spin-photon interfaces in the telecom band. 

Altermagnetism refers to a wide class of magnetic orders featuring magnetic sublattices with opposite spins related by rotational symmetries, resulting in nontrivial spin splitting and magnetic multipoles. However, the direct observation of the altermagnetic transition remains elusive. Here, by combining theoretical analysis, electrical transport, X-ray, and optical spectroscopies, we establish a phase diagram in hybrid molecular beam epitaxy-grown RuO₂/TiO₂(110) films, mapping symmetries along with altermagnetic/electronic/structural phase transitions as functions of film thickness and temperature. This features an altermagnetic metallic polar phase in epitaxially strained 2 nm films, suggesting a potential link between polar metals and altermagnetic materials. Such a clear signature of a magnetic phase transition at ~500 K is observed exclusively in ultrathin strained films, unlike in bulk RuO₂single crystals. These results highlight the power of epitaxial heterostructure engineering to induce altermagnetism in systems initially nonmagnetic, opening avenues for realizing emergent quantum phases with multifunctional properties. 

Infrared nanophotonics offers enormous potential for enhancing infrared optoelectronic technologies, due to the ability to confine light to deeply sub-wavelength dimensions. One of the limitations of traditional nanophotonics approaches is the inherent losses present in the plasmonic materials that are conventionally used. Surface phonon polaritons offer a lower-loss alternative but are more difficult to integrate with conventional III-V-based semiconductors used for infrared optoelectronics. In this work, we examine the properties of complex oxides, which can be grown directly onto III-V semiconductors for the purpose of infrared light detection. We grow films of both SrTiO₃and BaTiO₃on GaAs using pulsed laser deposition, and examine their properties using a combination of X-ray diffraction, atomic force microscopy, transmission electron microscopy, and infrared reflectance spectroscopy. We find that the films grown exhibit good crystallinity with smooth, uniform surfaces, and with occasional minor misoriented grains. Their optical properties indicate higher losses than perfect single crystal substrates, but by less than a factor of two, with phonon Q factors of 18-60, which is favorable when compared with plasmonic materials. We then conduct numerical simulations, which show that these films can be used to create surface phonon polariton infrared detectors that outperform similar metallic gratings by a factor of four. Our results show that the integration of oxide materials with conventional semiconductors is a viable route to improving infrared detector technology, competitive with other nanophotonics approaches.< 

A scalable platform to synthesize ultrathin heavy metals may enable high efficiency charge-to-spin conversion for next-generation spintronics. Here we report the synthesis of air-stable, epitaxially registered monolayer Pb underneath graphene on SiC (0001) by confinement heteroepitaxy (CHet). Diffraction, spectroscopy, and microscopy reveal CHet-based Pb intercalation predominantly exhibits a mottled hexagonal superstructure due to an ordered network of Frenkel-Kontorova-like domain walls. The system’s air stability enables ex-situ spin torque ferromagnetic resonance (ST-FMR) measurements that demonstrate charge-to-spin conversion in graphene/Pb/ferromagnet heterostructures with a 1.5× increase in the effective field ratio compared to control samples. 

Abstract Scaled and high‐quality insulators are crucial for fabricating 2D/3D hybrid vertical electronic devices such as metal‐oxide‐semiconductor (MOS) based Schottky diodes and hot electron transistors, the production of which is constrained by the scarcity of bulk layered wide bandgap semiconductors. In this research, the synthesis of a new 2D insulator, monolayer InO₂, which differs in stoichiometry from its bulk form is presented, over a large area (>300 µm²) by intercalating at the epitaxial graphene (EG)/SiC interface. By adjusting the lateral size of graphene through optical lithography prior to the intercalation, the thickness of InO₂is tuned such that it is 85% monolayer. The preference for monolayer formation of InO₂is explained using molecular dynamics and density functional theory (DFT) calculations. Additionally, the bandgap of InO₂is calculated to be 4.1 eV, differing from its bulk form (2.7 eV). Furthermore, MOS‐based Schottky diode measurements on InO₂intercalated EG/n‐SiC demonstrate that the EG/n‐SiC junction transforms from ohmic to a Schottky junction upon intercalation, with a barrier height of 0.87 eV and a rectification ratio of ≈10⁵. These findings introduce a new addition to the 2D insulator family, demonstrating the utility of monolayer InO₂as a barrier in vertical electronic devices. 

Abstract Highly-directional image artifacts such as ion mill curtaining, mechanical scratches, or image striping from beam instability degrade the interpretability of micrographs. These unwanted, aperiodic features extend the image along a primary direction and occupy a small wedge of information in Fourier space. Deleting this wedge of data replaces stripes, scratches, or curtaining, with more complex streaking and blurring artifacts—known within the tomography community as “missing wedge” artifacts. Here, we overcome this problem by recovering the missing region using total variation minimization, which leverages image sparsity-based reconstruction techniques—colloquially referred to as compressed sensing (CS)—to reliably restore images corrupted by stripe-like features. Our approach removes beam instability, ion mill curtaining, mechanical scratches, or any stripe features and remains robust at low signal-to-noise. The success of this approach is achieved by exploiting CS's inability to recover directional structures that are highly localized and missing in Fourier Space.