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In the rapidly evolving field of quantum computing, niobium nitride (NbN) superconductors have emerged as integral components due to their unique structural properties, including a high superconducting transition temperature (Tc), exceptional electrical conductivity, and compatibility with advanced device architectures. This study investigates the impact of high-temperature annealing and high-dose gamma irradiation on the structural, electrical, and superconducting properties of NbN films grown on GaN via reactive DC magnetron sputtering. The as-deposited cubic δ-NbN (111) films exhibited a high intensity distinct x-ray diffraction (XRD) peak, a high Tc of 12.82 K, and an atomically flat surface. Annealing at 500 and 950 °C for varying durations revealed notable structural and surface changes. High-resolution scanning transmission electron microscopy (STEM) indicated improved local ordering, while atomic force microscopy showed reduced surface roughness after annealing. X-ray photoelectron spectroscopy revealed a gradual increase in the Nb/N ratio with higher annealing temperatures and durations. High-resolution XRD and STEM analyses showed lattice constant modifications in δ-NbN films, attributed to residual stress changes following annealing. Additionally, XRD φ-scans revealed a sixfold symmetry in the NbN films due to rotational domains relative to GaN. While Tc remained stable after annealing at 500 °C, increasing the annealing temperature to 950 °C degraded Tc to 8.7 K and reduced the residual resistivity ratio from 0.85 in the as-deposited films to 0.29 after 30 min annealing. The effects of high-dose gamma radiation [5 Mrad (Si)] were also studied, demonstrating minimal changes to crystallinity and superconducting performance, indicating excellent radiation resilience. These findings highlight the potential of NbN superconductors for integration into advanced quantum devices and its suitability for applications in radiation-intensive environments such as space, satellites, and nuclear power plants. 

Precipitates have recently been found to significantly enhance the mechanical quality factor in piezoelectric ceramics. Such a piezoelectric hardening effect was attributed to strong interactions between ferroelectric domains and precipitates. In the present work, the response of domains to applied electric fields is observed in situ via transmission electron microscopy in aged (Ba, Ca)TiO3 ceramics with precipitates to reveal the underlying mechanism of this phenomenon. Ferroelectric domains in the Ba-rich matrix grain are observed to be more concentrated near non-polar Ca-rich precipitates. With increasing applied voltage, domains separate from precipitates merge together first, while those near precipitates persist to higher voltages. During ramping down, domains nucleate from precipitates. These direct observations confirm the strong interactions between ferroelectric domains and precipitates in piezoelectric ceramics. 

Kagome lattices have garnered substantial interest because their band structure consists of topological flat bands and Dirac cones. The RMn6Sn6 (R = rare earth) compounds are particularly interesting because of the existence of the large intrinsic anomalous Hall effect (AHE), which originates from the gapped Dirac cones near the Fermi level. This makes RMn6Sn6 an outstanding candidate for realizing the high-temperature quantum AHE. The growth of RMn6Sn6 thin films is beneficial for both fundamental research and potential applications. However, most of the studies on RMn6Sn6 have focused on bulk crystals, and the synthesis of RMn6Sn6 thin films has not been reported so far. Here, we report the atomic layer molecular beam epitaxy growth, structural and magnetic characterizations, and transport properties of ErMn6Sn6 and TbMn6Sn6 thin films. It is especially noteworthy that TbMn6Sn6 thin films have out-of-plane magnetic anisotropy, which is important for realizing the quantum AHE. Our work paves the avenue toward the control of the AHE using devices patterned from RMn6Sn6 thin films. 

Defects are essential to engineering the properties of functional materials ranging from semiconductors and superconductors to ferroics. Whereas point defects have been widely exploited, dislocations are commonly viewed as problematic for functional materials and not as a microstructural tool. We developed a method for mechanically imprinting dislocation networks that favorably skew the domain structure in bulk ferroelectrics and thereby tame the large switching polarization and make it available for functional harvesting. The resulting microstructure yields a strong mechanical restoring force to revert electric field–induced domain wall displacement on the macroscopic level and high pinning force on the local level. This induces a giant increase of the dielectric and electromechanical response at intermediate electric fields in barium titanate [electric field–dependent permittivity (ε₃₃) ≈ 5800 and large-signal piezoelectric coefficient (d₃₃*) ≈ 1890 picometers/volt]. Dislocation-based anisotropy delivers a different suite of tools with which to tailor functional materials.