First Direct Observation of Nanometer size Hydride Precipitations on Superconducting Niobium

Superconducting niobium serves as a key enabling material for superconducting radio frequency (SRF) technology as well as quantum computing devices. At room temperature, hydrogen commonly occupies tetragonal sites in the Nb lattice as metal (M)-gas (H) phase. When the temperature is decreased, however, solid solution of Nb-H starts to be precipitated. In this study, we show the first identified topographical features associated with nanometer-size hydride phase (Nb1-xHx) precipitates on metallic superconducting niobium using cryogenic-atomic force microscopy (AFM). Further, high energy grazing incidence X-ray diffraction reveals information regarding the structure and stoichiometry that these precipitates exhibit. Finally, through time-of-flight secondary ion mass spectroscopy (ToF-SIMS), we are able to locate atomic hydrogen sources near the top surface. This systematic study further explains localized degradation of RF superconductivity by the proximity effect due to hydrogen clusters

A magnetic Weyl semimetallic phase in thin films of Eu2_2Ir2_2O7_7

The interplay between electronic interactions and strong spin-orbit coupling is expected to create a plethora of fascinating correlated topological states of quantum matter. Of particular interest are magnetic Weyl semimetals originally proposed in the pyrochlore iridates, which are only expected to reveal their topological nature in thin film form. To date, however, direct experimental demonstrations of these exotic phases remain elusive, due to the lack of usable single crystals and the insufficient quality of available films. Here, we report on the discovery of the long-sought magnetic Weyl semi-metallic phase in (111)-oriented Eu$_2$Ir$_2$O$_7$ high-quality epitaxial thin films. The topological magnetic state shows an intrinsic anomalous Hall effect with colossal coercivity but vanishing net magnetization, which emerges below the onset of a peculiar magnetic phase with all-in-all-out antiferromagnetic ordering. The observed anomalous Hall conductivity arises from the non-zero Berry curvature emanated by Weyl node pairs near the Fermi level that act as sources and sinks of Berry flux, activated by broken cubic crystal symmetry at the top and bottom terminations of the thin film

Single-Crystalline SrRuO₃ Nanomembranes: A Platform for Flexible Oxide Electronics

The field of oxide electronics has benefited from the wide spectrum of functionalities available to the ABO₃ perovskites, and researchers are now employing defect engineering in single crystalline heterostructures to tailor properties. However, bulk oxide single crystals are not conducive to many types of applications, particularly those requiring mechanical flexibility. Here, we demonstrate the realization of an all-oxide, single-crystalline nanomembrane heterostructure. With a surface-to-volume ratio of 2 × 10⁷, the nanomembranes are fully flexible and can be readily transferred to other materials for handling purposes or for new materials integration schemes. Using <i>in situ</i> synchrotron X-ray scattering, we find that the nanomembranes can bond to other host substrates near room temperature and demonstrate coupling between surface reactivity and electromechanical properties in ferroelectric nanomembrane systems. The synthesis technique described here represents a significant advancement in materials integration and provides a new platform for the development of flexible oxide electronics

Solvent Influence on the Magnetization and Phase of Fe-Ni Alloy Nanoparticles Generated by Laser Ablation in Liquids

The synthesis of bimetallic iron-nickel nanoparticles with control over the synthesized phases, particle size, surface chemistry, and oxidation level remains a challenge that limits the application of these nanoparticles. Pulsed laser ablation in liquid allows the properties tuning of the generated nanoparticles by changing the ablation solvent. Organic solvents such as acetone can minimize nanoparticle oxidation. Yet, economical laboratory and technical grade solvents that allow cost-effective production of FeNi nanoparticles contain water impurities, which are a potential source of oxidation. Here, we investigated the influence of water impurities in acetone on the properties of FeNi nanoparticles generated by pulsed laser ablation in liquids. To remove water impurities and produce “dried acetone”, cost-effective and reusable molecular sieves (3 Å) are employed. The results show that the Fe50Ni50 nanoparticles’ properties are influenced by the water content of the solvent. The metastable HCP FeNi phase is found in NPs prepared in acetone, while only the FCC phase is observed in NPs formed in water. Mössbauer spectroscopy revealed that the FeNi nanoparticles oxidation in dried acetone is reduced by 8% compared to acetone. The high-field magnetization of Fe50Ni50 nanoparticles in water is the highest, 68 Am2/kg, followed by the nanoparticles obtained after ablation in acetone without water impurities, 59 Am2/kg, and acetone, 52 Am2/kg. The core-shell structures formed in these three liquids are also distinctive, demonstrating that a core-shell structure with an outer oxide layer is formed in water, while carbon external layers are obtained in acetone without water impurity. The results confirm that the size, structure, phase, and oxidation of FeNi nanoparticles produced by pulsed laser ablation in liquids can be modified by changing the solvent or just reducing the water impurities in the organic solvent

Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

Characterization of the periodicity and strain state of an array of lithographically patterned silicon and silicon-germanium alloy on silicon fins using reciprocal space mapping of Bragg diffraction peaks is presented. Various patterned structures with different pitch values of 90 nm, 65 nm, and 42 nm have been studied and data for the 42 nm pitch sample is discussed in this paper. Diffraction from fin arrays is treated kinematically analogous to periodic surface grating structures. Diffraction from the symmetric 004 planes is used to calculate pitch and analyze the pitch walking pattern which appears as harmonic peaks on either side of the fin peaks. Pitch walking refers to the presence of two periodicities in the array due to the lithographic process. Longitudinal scans are evaluated at the fin peak positions to probe into the shape of the fin structure. Nonrectangular fin shapes resulted in peak splitting of the longitudinal scans of higher order fin peaks indicating a finite sidewall slope. Asymmetric 224 planes were analyzed to study the quality and strain-relaxation of the fin structures both parallel and perpendicular to the fin length using reciprocal space mapping techniques.College of Nanoscale Science and Engineering, SUNY, New York 12203 GLOBALFOUNDRIES, Albany, New York 12203 Jordan Valley Semiconductors Inc., 3913 Todd Lane, Suite 106, Austin, Texas 78744 Advanced Photon Source, Argonne National Laboratory, 9700S Cass Ave., Argonne, Illinois 6043