Josephson effects in MgB2 meta masked ion damage junctions

Ion beam damage combined with nanoscale focused ion beam direct milling was used to create manufacturable SNS type Josephson junctions in 100 nm thick MgB$_{2}$ with T$_{C}$ of 38 K. The junctions show non-hysteretic current - voltage characteristics between 36 and 4.2 K. Experimental evidence for the dc and ac Josephson effects in MgB$_{2}$ metal masked ion damage junctions are presented. This technique is particularly useful for prototyping devices due to its simplicity and flexibility of fabrication and has a great potential for high-density integration.Comment: 12 pages, 4 figures, RevTeX4, submitted to AP

Preferred location for conducting filament formation in thin-film nano-ionic electrolyte: study of microstructure by atom-probe tomography

© 2017, The Author(s). Atom-probe tomography of Ag-photodoped amorphous thin-film Ge 40 S 60 , the material of interest in nano-ionic memory and lateral geometry MEMS technologies, reveals regions with two distinct compositions on a nanometer length-scale. One type of region is Ag-rich and of a size typically extending beyond the measured sample volume of ~40 × 40 × 80 nm 3 . These type-I regions contain aligned nanocolumns, ~5 nm wide, that are the likely location for reversible diffusion of Ag + ions and associated growth/dissolution of conducting filaments. The nanocolumns become relatively Ag-rich during the photodoping, and the pattern of Ag enrichment originates from the columnar-porous structure of the as-deposited film that is to some extent preserved in the electrolyte after photodoping. Type-II regions have lower Ag content, are typically 10–20 nm across, and appear to conform to the usual description of the photoreaction products of the optically-induced dissolution and diffusion of silver in a thin-film chalcogenide. The microstructure, with two types of region and aligned nanocolumns, is present in the electrolyte after photodoping without any applied bias, and is important for understanding switching mechanisms, and writing and erasing cycles, in programmable-metallization-cell memory

Growth of Strongly Biaxially Aligned MgB2 Thin Films on Sapphire by Post-annealing of Amorphous Precursors

MgB2 thin films were cold-grown on sapphire substrates by pulsed laser deposition (PLD), followed by post-annealing in mixed, reducing gas, Mg-rich, Zr gettered, environments. The films had Tcs in the range 29 K to 34 K, Jcs (20K, H=0) in the range 30 kA/cm2 to 300 kA/cm2, and irreversibility fields at 20 K of 4 T to 6.2 T. An inverse correlation was found between Tc and irreversibility field. The films had grain sizes of 0.1-1 micron and a strong biaxial alignment was observed in the 950C annealed film.Comment: 12 Pages, 5 figures, submitted to Applied Physics Letter

Large magnetoelectric coupling in multiferroic oxide heterostructures assembled via epitaxial lift-off.

Epitaxial films may be released from growth substrates and transferred to structurally and chemically incompatible substrates, but epitaxial films of transition metal perovskite oxides have not been transferred to electroactive substrates for voltage control of their myriad functional properties. Here we demonstrate good strain transmission at the incoherent interface between a strain-released film of epitaxially grown ferromagnetic La0.7Sr0.3MnO3 and an electroactive substrate of ferroelectric 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 in a different crystallographic orientation. Our strain mediated magnetoelectric coupling compares well with respect to epitaxial heterostructures, where the epitaxy responsible for strong coupling can degrade film magnetization via strain and dislocations. Moreover, the electrical switching of magnetic anisotropy is repeatable and non volatile. High resolution magnetic vector maps reveal that micromagnetic behaviour is governed by electrically controlled strain and film microstructure. Our demonstration should permit the physical/chemical properties in strain-released epitaxial oxide films to be controlled using electroactive substrates to impart strain via non epitaxial interfaces.Beatriu de Pinós postdoctoral fellowship (2014 BP-A 00079) from the Catalan government via the Agència de Gestió d’Ajuts Universitaris i de Recerca (AGAUR); Ministry of Science and Higher Education of Russian Federation, goszadanie no. 2019-1246; the Royal Society; EPSRC (Grant EP/P009050/1, EP/M010619/1 and the NoWNano DTC); European Research Council (ERC) (ERC-2016-STG-EvoluTEM-715502 and ERC Synergy HETERO2D); “la Caixa” Foundation (ID 100010434)

Preferred location for conducting filament formation in thin-film nano-ionic electrolyte: study of microstructure by atom-probe tomography

© 2017, The Author(s). Atom-probe tomography of Ag-photodoped amorphous thin-film Ge 40 S 60 , the material of interest in nano-ionic memory and lateral geometry MEMS technologies, reveals regions with two distinct compositions on a nanometer length-scale. One type of region is Ag-rich and of a size typically extending beyond the measured sample volume of ~40 × 40 × 80 nm 3 . These type-I regions contain aligned nanocolumns, ~5 nm wide, that are the likely location for reversible diffusion of Ag + ions and associated growth/dissolution of conducting filaments. The nanocolumns become relatively Ag-rich during the photodoping, and the pattern of Ag enrichment originates from the columnar-porous structure of the as-deposited film that is to some extent preserved in the electrolyte after photodoping. Type-II regions have lower Ag content, are typically 10–20 nm across, and appear to conform to the usual description of the photoreaction products of the optically-induced dissolution and diffusion of silver in a thin-film chalcogenide. The microstructure, with two types of region and aligned nanocolumns, is present in the electrolyte after photodoping without any applied bias, and is important for understanding switching mechanisms, and writing and erasing cycles, in programmable-metallization-cell memory

In situ observation of the effect of nitrogen on carbon nanotube synthesis

The article examines the in situ observation of the effect of nitrogen on carbon nanotube synthesis. Environmental TEM (ETEM) is a relatively new technique ideal for in situ measurements. Researchers apply ETEM to study the effect of nitrogen on CNT growth, elucidating the mechanisms by which nitrogen acts, to guide efforts to optimize synthesis. To the best of our knowledge, this is the first in situ TEM study of the effect of nitrogen on CNT growth. Therefore, in the absence of ammonia, carbon should precipitate first, resulting in an interface with pure iron. Pure iron has a higher surface tension with the nanotube, which explains the separation of the CNT and catalyst immediately following carbon precipitation. A carbide particle will have a lower surface tension with the nanotube due to its higher carbon chemical potential and thus maintain its contact. The pure iron catalyst may become carbide following cap separation, but this will not affect CNT nucleation

Preferred location for conducting filament formation in thin-film nano-ionic electrolyte: study of microstructure by atom-probe tomography

© 2017, The Author(s). Atom-probe tomography of Ag-photodoped amorphous thin-film Ge 40 S 60 , the material of interest in nano-ionic memory and lateral geometry MEMS technologies, reveals regions with two distinct compositions on a nanometer length-scale. One type of region is Ag-rich and of a size typically extending beyond the measured sample volume of ~40 × 40 × 80 nm 3 . These type-I regions contain aligned nanocolumns, ~5 nm wide, that are the likely location for reversible diffusion of Ag + ions and associated growth/dissolution of conducting filaments. The nanocolumns become relatively Ag-rich during the photodoping, and the pattern of Ag enrichment originates from the columnar-porous structure of the as-deposited film that is to some extent preserved in the electrolyte after photodoping. Type-II regions have lower Ag content, are typically 10–20 nm across, and appear to conform to the usual description of the photoreaction products of the optically-induced dissolution and diffusion of silver in a thin-film chalcogenide. The microstructure, with two types of region and aligned nanocolumns, is present in the electrolyte after photodoping without any applied bias, and is important for understanding switching mechanisms, and writing and erasing cycles, in programmable-metallization-cell memory

Enhanced controllable triplet proximity effect in superconducting spin–orbit coupled spin valves with modified superconductor/ferromagnet interfaces

In a superconductor/ferromagnet hybrid, a magnetically controlled singlet-to-triplet Cooper pair conversion can modulate the superconducting critical temperature. In these triplet superconducting spin valves, such control usually requires inhomogeneous magnetism. However, in the presence of spin–orbit coupling from an interfacial heavy metal layer, the singlet/triplet conversion rate and, thus, critical temperature can be controlled via the magnetization direction of a single homogeneous ferromagnet. Here, we report significantly enhanced controllable pair conversion to a triplet state in a Nb/Pt/Co/Pt superconducting spin valve in which Pt/Co/Pt is homogenously magnetized and proximity-coupled to a superconducting layer of Nb. The Co/Pt interface furthest away from Nb is modified by a sub-nanometer-thick layer of Cu or Au. We argue that the enhancement is most likely associated from an improvement of the Co/Pt interface due to the insertion of Cu and Au layers. Additionally, the higher normalized orbital moments in Au measured using x-ray magnetic circular dichroism shows that increasing spin–orbit coupling enhances the triplet proximity effect—an observation supported by our theoretical calculations. Our results provide a pathway to enhancing triplet pair creation by interface engineering for device development in superspintronics.</p