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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Methods to Create Novel La 2- x Sr x CuO 4 Devices with Multiple Atomically Sharp Interfaces

We present methods to create devices that utilize the high-temperature superconductor La 2-x Sr x CuO 4 grown by atomic layer-by-layer molecular beam epitaxy (ALL-MBE). The ALL-MBE synthesis technique provides atomically precise interfaces necessary for the tunnel junctions, Josephson junctions, and dyon detection devices that will be considered. A series of microfabrication processing steps using established techniques are given for each device, and their details are discussed. These procedures are easily extended to generate more complex designs and could be suitable for a wider variety of materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Effects of Focused Ion Beam Lithography on La 2– x Sr x CuO 4 Single Crystals

Focused ion beam (FIB) milling is a mask-free lithography technique that allows the precise shaping of 3D materials on the micron and sub-micron scale. The recent discovery of electronic nematicity in La 2–x Sr x CuO 4 (LSCO) thin films triggered the search for the same phenomenon in bulk LSCO crystals. With this motivation, we have systematically explored FIB patterning of bulk LSCO crystals into micro-devices suitable for longitudinal and transverse resistivity measurements. We found that several detrimental factors can affect the result, ultimately compromising the possibility of effectively using FIB milling to fabricate sub-micrometer LSCO devices, especially in the underdoped regime.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Atomic-Layer Engineering of La 2-x Sr x CuO 4 —La 2-x Sr x ZnO 4 Heterostructures

The fabrication of trilayer superconductor-insulator-superconductor (SIS) Josephson junctions with high-temperature superconductor (HTS) electrodes requires atomically perfect interfaces. Therefore, despite great interest and efforts, this remained a challenge for over three decades. Here, we report the discovery of a new family of metastable materials, La 2-x Sr x ZnO 4 (LSZO), synthesized by atomic-layer-by-layer molecular beam epitaxy (ALL-MBE). We show that LSZO is insulating and epitaxially compatible with an HTS compound, La 2-x Sr x CuO 4 (LSCO). Since the “parent” compound La 2-x Sr x ZnO 4 (LZO) is easier to grow, here we focus on this material as our insulating layer. Growing LZO at very low temperatures to reduce cation interdiffusion makes LSCO/LZO interfaces atomically sharp. We show that in LSCO/LZO/LSCO trilayers, the superconducting properties of the LSCO electrodes remain undiminished, unlike in previous attempts with insulator barriers made of other materials. This opens prospects to produce high-quality HTS tunnel junctions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Probing the surface of promoted CuO-Cr 2 O 3 -Fe 2 O 3 catalysts during CO 2 activation

The influence of basic oxide promoters on copper-chromium-iron oxide catalysts was investigated to determine the nature of surface oxygen species and structure-activity relationship for the reverse water-gas shift reaction. The catalysts were characterized with in situ XRD, in situ Raman, in situ XPS, in situ HS-LEIS and H 2 -TPR. Two surface oxygen sites with different reduction characteristics were found to be present. The overall CO 2 activation rate was found to correlate with both the number and reducibility of the more active oxygen species that were likely associated with the Cu-FeO x interfacial regions for enhanced hydrogen spillover. While addition of K 2 O somewhat preserved the interfacial regions and facilitated the reduction kinetics of surface oxygen, both Na 2 O and CaO significantly suppressed the availability of metallic Cu as well as the Cu-FeO x interfaces, leading to decreased reactivity. These findings provide a direction to promote the copper-iron catalysts by creating more metal-metal oxide interfacial sites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Li(CuO)2 by Materials Project

LiCu2O2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Li1+ is bonded to five O2- atoms to form LiO5 square pyramids that share corners with four equivalent CuO5 square pyramids, edges with four equivalent LiO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are a spread of Li–O bond distances ranging from 2.08–2.12 Å. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded to five O2- atoms to form distorted CuO5 square pyramids that share corners with four equivalent LiO5 square pyramids, edges with four equivalent LiO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are a spread of Cu–O bond distances ranging from 1.99–2.64 Å. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.86 Å) and one longer (1.88 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and four Cu+1.50+ atoms. In the second O2- site, O2- is bonded to three equivalent Li1+ and three Cu+1.50+ atoms to form edge-sharing OLi3Cu3 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CuO)2 by Materials Project

NaCu2O2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Na1+ is bonded to five O2- atoms to form distorted edge-sharing NaO5 square pyramids. There are two shorter (2.32 Å) and three longer (2.39 Å) Na–O bond lengths. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (1.99 Å) and two longer (2.02 Å) Cu–O bond lengths. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.85 Å) and one longer (1.87 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Na1+ and three Cu+1.50+ atoms to form ONa3Cu3 octahedra that share corners with seven equivalent ONa2Cu3 square pyramids, edges with four equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. In the second O2- site, O2- is bonded to two equivalent Na1+ and three Cu+1.50+ atoms to form ONa2Cu3 square pyramids that share corners with seven equivalent ONa3Cu3 octahedra, edges with two equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. The corner-sharing octahedra tilt angles range from 0–76°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(CuO)2 by Materials Project

LiCu2O2 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Li1+ is bonded to five O2- atoms to form LiO5 square pyramids that share corners with four equivalent CuO5 square pyramids, edges with four equivalent LiO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are a spread of Li–O bond distances ranging from 2.08–2.12 Å. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.86 Å) and one longer (1.88 Å) Cu–O bond length. In the second Cu+1.50+ site, Cu+1.50+ is bonded to five O2- atoms to form distorted CuO5 square pyramids that share corners with four equivalent LiO5 square pyramids, edges with four equivalent LiO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are a spread of Cu–O bond distances ranging from 1.99–2.61 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to two equivalent Li1+ and four Cu+1.50+ atoms. In the second O2- site, O2- is bonded to three equivalent Li1+ and three Cu+1.50+ atoms to form edge-sharing OLi3Cu3 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(CuO)2 by Materials Project

NaCu2O2 crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. Na1+ is bonded to five O2- atoms to form edge-sharing NaO5 square pyramids. There are a spread of Na–O bond distances ranging from 2.31–2.40 Å. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a square co-planar geometry to four O2- atoms. There are two shorter (2.00 Å) and two longer (2.03 Å) Cu–O bond lengths. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.85 Å) and one longer (1.86 Å) Cu–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Na1+ and three Cu+1.50+ atoms to form ONa3Cu3 octahedra that share corners with seven equivalent ONa2Cu3 square pyramids, edges with four equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. In the second O2- site, O2- is bonded to two equivalent Na1+ and three Cu+1.50+ atoms to form distorted ONa2Cu3 square pyramids that share corners with seven equivalent ONa3Cu3 octahedra, edges with two equivalent ONa3Cu3 octahedra, and edges with two equivalent ONa2Cu3 square pyramids. The corner-sharing octahedra tilt angles range from 0–80°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CuO)2 by Materials Project

BaCu2O2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Ba2+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing BaO6 octahedra. The corner-sharing octahedral tilt angles are 5°. There are two shorter (2.66 Å) and four longer (2.90 Å) Ba–O bond lengths. Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.85 Å. O2- is bonded to three equivalent Ba2+ and two equivalent Cu1+ atoms to form a mixture of distorted edge and corner-sharing OBa3Cu2 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(CuO)3 by Materials Project

LiCu3O3 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Li1+ is bonded to five O2- atoms to form distorted corner-sharing LiO5 trigonal bipyramids. There are four shorter (2.04 Å) and one longer (2.13 Å) Li–O bond lengths. There are three inequivalent Cu+1.67+ sites. In the first Cu+1.67+ site, Cu+1.67+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.86 Å. In the second Cu+1.67+ site, Cu+1.67+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.99 Å. In the third Cu+1.67+ site, Cu+1.67+ is bonded in a distorted rectangular see-saw-like geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.98 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Li1+ and three Cu+1.67+ atoms to form distorted OLi2Cu3 trigonal bipyramids that share corners with two equivalent OLiCu4 square pyramids, corners with five equivalent OLi2Cu3 trigonal bipyramids, and edges with four equivalent OLi2Cu3 trigonal bipyramids. In the second O2- site, O2- is bonded to one Li1+ and four equivalent Cu+1.67+ atoms to form distorted OLiCu4 square pyramids that share corners with four equivalent OLiCu4 square pyramids, corners with four equivalent OLi2Cu3 trigonal bipyramids, and edges with four equivalent OLiCu4 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(CuO)2 by Materials Project

CaCu2O2 crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Ca2+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing CaO6 octahedra. The corner-sharing octahedral tilt angles are 5°. There are two shorter (2.27 Å) and four longer (2.67 Å) Ca–O bond lengths. Cu1+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.86 Å. O2- is bonded to three equivalent Ca2+ and two equivalent Cu1+ atoms to form a mixture of distorted edge and corner-sharing OCa3Cu2 trigonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(CuO)3 by Materials Project

LiCu3O3 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to five O2- atoms to form distorted corner-sharing LiO5 trigonal bipyramids. There are four shorter (2.04 Å) and one longer (2.11 Å) Li–O bond lengths. In the second Li1+ site, Li1+ is bonded to five O2- atoms to form distorted LiO5 trigonal bipyramids that share corners with five equivalent LiO5 trigonal bipyramids and edges with four equivalent CuO5 square pyramids. There are four shorter (2.05 Å) and one longer (2.23 Å) Li–O bond lengths. There are five inequivalent Cu+1.67+ sites. In the first Cu+1.67+ site, Cu+1.67+ is bonded in a linear geometry to two O2- atoms. Both Cu–O bond lengths are 1.86 Å. In the second Cu+1.67+ site, Cu+1.67+ is bonded in a distorted square co-planar geometry to four O2- atoms. All Cu–O bond lengths are 1.98 Å. In the third Cu+1.67+ site, Cu+1.67+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.99 Å. In the fourth Cu+1.67+ site, Cu+1.67+ is bonded to five O2- atoms to form distorted CuO5 square pyramids that share corners with five equivalent CuO5 square pyramids and edges with four equivalent LiO5 trigonal bipyramids. There are four shorter (1.98 Å) and one longer (2.68 Å) Cu–O bond lengths. In the fifth Cu+1.67+ site, Cu+1.67+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.98 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Li1+ and three Cu+1.67+ atoms to form distorted OLi2Cu3 trigonal bipyramids that share corners with two equivalent OLiCu4 square pyramids, corners with five OLi2Cu3 trigonal bipyramids, and edges with four equivalent OLi2Cu3 trigonal bipyramids. In the second O2- site, O2- is bonded to two equivalent Li1+ and three Cu+1.67+ atoms to form distorted OLi2Cu3 trigonal bipyramids that share corners with four OCu6 octahedra, corners with five OLi2Cu3 trigonal bipyramids, and edges with four equivalent OLi2Cu3 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 76–88°. In the third O2- site, O2- is bonded to six Cu+1.67+ atoms to form distorted OCu6 octahedra that share corners with four equivalent OCu6 octahedra, corners with eight equivalent OLi2Cu3 trigonal bipyramids, and edges with four equivalent OLi2Cu4 octahedra. The corner-sharing octahedral tilt angles are 0°. In the fourth O2- site, O2- is bonded to one Li1+ and four equivalent Cu+1.67+ atoms to form OLiCu4 square pyramids that share corners with four equivalent OLiCu4 square pyramids, corners with four equivalent OLi2Cu3 trigonal bipyramids, and edges with four equivalent OLiCu4 square pyramids. In the fifth O2- site, O2- is bonded to two equivalent Li1+ and four equivalent Cu+1.67+ atoms to form OLi2Cu4 octahedra that share corners with four equivalent OLi2Cu4 octahedra, corners with eight equivalent OLi2Cu3 trigonal bipyramids, and edges with four equivalent OCu6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(CuO)3 by Materials Project

LiCu3O3 crystallizes in the tetragonal P4mm space group. The structure is three-dimensional. Li1+ is bonded to five O2- atoms to form LiO5 square pyramids that share a cornercorner with one CuO5 square pyramid, corners with four equivalent LiO5 square pyramids, edges with four equivalent LiO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are four shorter (2.03 Å) and one longer (2.25 Å) Li–O bond lengths. There are three inequivalent Cu+1.67+ sites. In the first Cu+1.67+ site, Cu+1.67+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.80 Å) and one longer (1.89 Å) Cu–O bond length. In the second Cu+1.67+ site, Cu+1.67+ is bonded to five O2- atoms to form CuO5 square pyramids that share a cornercorner with one LiO5 square pyramid, corners with eight CuO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are four shorter (2.04 Å) and one longer (2.37 Å) Cu–O bond lengths. In the third Cu+1.67+ site, Cu+1.67+ is bonded to five O2- atoms to form distorted CuO5 square pyramids that share corners with eight CuO5 square pyramids, edges with four equivalent LiO5 square pyramids, and edges with four equivalent CuO5 square pyramids. There are four shorter (2.03 Å) and one longer (2.24 Å) Cu–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Li1+ and two Cu+1.67+ atoms to form distorted OLi4Cu2 octahedra that share corners with four equivalent OLi4Cu2 octahedra, a cornercorner with one OCu5 square pyramid, and edges with eight OLi4Cu2 octahedra. The corner-sharing octahedral tilt angles are 13°. In the second O2- site, O2- is bonded to five Cu+1.67+ atoms to form distorted OCu5 square pyramids that share corners with five OLi4Cu2 octahedra, corners with four equivalent OCu5 square pyramids, and edges with four equivalent OCu5 square pyramids. The corner-sharing octahedra tilt angles range from 0–83°. In the third O2- site, O2- is bonded to one Li1+ and five Cu+1.67+ atoms to form OLiCu5 octahedra that share corners with four equivalent OLiCu5 octahedra, corners with four equivalent OCu5 square pyramids, and edges with eight OLi4Cu2 octahedra. The corner-sharing octahedral tilt angles are 13°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li(CuO)3 by Materials Project

LiCu3O3 crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Li1+ is bonded to six equivalent O2- atoms to form corner-sharing LiO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Li–O bond lengths are 2.03 Å. Cu+1.67+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 2.03 Å. O2- is bonded to two equivalent Li1+ and four equivalent Cu+1.67+ atoms to form a mixture of edge and corner-sharing OLi2Cu4 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Effect of redox promoters (CeO x and CuO x ) and surface sulfates on the selective catalytic reduction (SCR) of NO with NH 3 by supported V 2 O 5 -WO 3 /TiO 2 catalysts

A series of TiO 2 -supported MO x catalysts (M=V, W, Ce, Cu and S) were investigated for their SCR activity. In situ Raman spectroscopy indicated that the supported MO x phases were completely dispersed as surface sites on the TiO 2 support. In situ IR revealed that surface VO x , WO x and SO x sites anchored at both CeO x /CuO x and TiO 2 sites. The number of surface Lewis acid sites decreased with the addition of basic (CeO x /CuO x ) and acidic (VO x /WO x ) sites in all catalysts, and acidic SO x in the unpromoted and Ce-promoted catalysts. The surface VO x , WO x and SO x sites introduced surface Brønsted acid sites. The redox promoters increased the NO conversion, but SO x impregnation inhibited their effect due to acid (SO x )-base (CeO x /CuO x ) interactions. Finally, the SCR reaction was shown to efficiently proceed via either surface NH 3 * or NH 4 +* species, resolving the long-standing dispute on the involvement of these species in the SCR reaction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗