scholarly journals Novel synthesis approach for “stubborn” metals and metal oxides

2021 ◽  
Vol 118 (32) ◽  
pp. e2105713118
Author(s):  
William Nunn ◽  
Anusha Kamath Manjeshwar ◽  
Jin Yue ◽  
Anil Rajapitamahuni ◽  
Tristan K. Truttmann ◽  
...  
Keyword(s):  
Vapor Pressure ◽  
Physical Vapor Deposition ◽  
Materials Science ◽  
Residual Resistivity ◽  
Residual Resistivity Ratio ◽  
Major Step ◽  
Resistivity Ratio ◽  
Metal Oxide Thin Films ◽  
Complex Metal Oxide ◽  
Synthesis Approach

Advances in physical vapor deposition techniques have led to a myriad of quantum materials and technological breakthroughs, affecting all areas of nanoscience and nanotechnology which rely on the innovation in synthesis. Despite this, one area that remains challenging is the synthesis of atomically precise complex metal oxide thin films and heterostructures containing “stubborn” elements that are not only nontrivial to evaporate/sublimate but also hard to oxidize. Here, we report a simple yet atomically controlled synthesis approach that bridges this gap. Using platinum and ruthenium as examples, we show that both the low vapor pressure and the difficulty in oxidizing a “stubborn” element can be addressed by using a solid metal-organic compound with significantly higher vapor pressure and with the added benefits of being in a preoxidized state along with excellent thermal and air stability. We demonstrate the synthesis of high-quality single crystalline, epitaxial Pt, and RuO2 films, resulting in a record high residual resistivity ratio (=27) in Pt films and low residual resistivity, ∼6 μΩ·cm, in RuO2 films. We further demonstrate, using SrRuO3 as an example, the viability of this approach for more complex materials with the same ease and control that has been largely responsible for the success of the molecular beam epitaxy of III-V semiconductors. Our approach is a major step forward in the synthesis science of “stubborn” materials, which have been of significant interest to the materials science and the condensed matter physics community.

scholarly journals Proximity effect in [Nb(1.5 nm)/Fe(x)]10/Nb(50 nm) superconductor/ferromagnet heterostructures

2020 ◽  
Vol 11 ◽  
pp. 1254-1263
Author(s):  
Yury Khaydukov ◽  
Sabine Pütter ◽  
Laura Guasco ◽  
Roman Morari ◽  
Gideok Kim ◽  
...  
Keyword(s):  
Intermediate State ◽  
Proximity Effect ◽  
Intermediate Phase ◽  
Ferromagnetic Layer ◽  
Residual Resistivity ◽  
Neutron Reflectometry ◽  
Superconducting Transition ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Weak Ferromagnetic

We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe(x)]10 superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al2O3(1−102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15–20. By using neutron reflectometry we show that Fe/Nb superlattices with x < 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to x = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure.

Origin of Diversified Transport Properties of MgB2

2003 ◽  
Vol 17 (18n20) ◽  
pp. 3672-3674
Author(s):  
Kijoon H. P. Kim ◽  
C. U. Jung ◽  
Heon-Jung Kim ◽  
Min-Seok Park ◽  
Mun-Seog Kim ◽  
...  
Keyword(s):  
Low Temperature ◽  
Transport Properties ◽  
Temperature Region ◽  
Residual Resistivity ◽  
Transition Width ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Excess Mg

We investigated the transport properties of MgB 2 while changing the contents of excess Mg. The samples containing almost no excess Mg showed the highest Tc and the sharpest transition width (ΔTc). A residual resistivity ratio (RRR) of ~ 5.8, and a magnetoresistance (MR) of 12%, at 40 K, were obtained for this stoichiometric sample. Moreover, no upturn of resistivity in a low temperature region at 10 Tesla was observed. However, the samples containing appreciable amounts of excess Mg showed quite different behaviors; the values of ΔTc, RRR and MR were much larger. Surprisingly, big upturn appeared in this Mg-excess MgB 2

scholarly journals High-sensitivity of initial SrO growth on the residual resistivity in epitaxial thin films of SrRuO$$_3$$ on SrTiO$$_3$$ (001)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Uddipta Kar ◽  
Akhilesh Kr. Singh ◽  
Song Yang ◽  
Chun-Yen Lin ◽  
Bipul Das ◽  
...  
Keyword(s):  
Volume Fraction ◽  
High Sensitivity ◽  
Orthorhombic Phase ◽  
Residual Resistivity ◽  
Epitaxial Thin Films ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Growth Technique ◽  
X Ray ◽  
High Crystallinity

AbstractThe growth of SrRuO$$_3$$ 3 (SRO) thin film with high-crystallinity and low residual resistivity (RR) is essential to explore its intrinsic properties. Here, utilizing the adsorption-controlled growth technique, the growth condition of initial SrO layer on TiO$$_2$$ 2 -terminated SrTiO$$_3$$ 3 (STO) (001) substrate was found to be crucial for achieving a low RR in the resulting SRO film grown afterward. The optimized initial SrO layer shows a c(2 $$\times $$ × 2) superstructure that was characterized by electron diffraction, and a series of SRO films with different thicknesses (ts) were then grown. The resulting SRO films exhibit excellent crystallinity with orthorhombic-phase down to $$t \approx $$ t ≈ 4.3 nm, which was confirmed by high resolution X-ray measurements. From X-ray azimuthal scan across SRO orthorhombic (02 ± 1) reflections, we uncover four structural domains with a dominant domain of orthorhombic SRO [001] along cubic STO [010] direction. The dominant domain population depends on t, STO miscut angle ($$\alpha $$ α ), and miscut direction ($$\beta $$ β ), giving a volume fraction of about 92 $$\%$$ % for $$t \approx $$ t ≈ 26.6 nm and $$(\alpha , \beta ) \approx $$ ( α , β ) ≈ (0.14$$^{\mathrm{o}}$$ o , 5$$^{\mathrm{o}}$$ o ). On the other hand, metallic and ferromagnetic properties were well preserved down to t$$\approx $$ ≈ 1.2 nm. Residual resistivity ratio (RRR = $$\rho ({\mathrm{300 K}})$$ ρ ( 300 K ) /$$\rho ({\mathrm{5K}})$$ ρ ( 5 K ) ) reduces from 77.1 for t$$\approx $$ ≈ 28.5 nm to 2.5 for t$$\approx $$ ≈ 1.2 nm, while $$\rho ({\mathrm{5K}})$$ ρ ( 5 K ) increases from 2.5 $$\upmu \Omega $$ μ Ω cm for t$$\approx $$ ≈ 28.5 nm to 131.0 $$\upmu \Omega $$ μ Ω cm for t$$\approx $$ ≈ 1.2 nm. The ferromagnetic onset temperature ($$T'_{\mathrm{c}}$$ T c ′ ) of around 151 K remains nearly unchanged down to t$$\approx $$ ≈ 9.0 nm and decreases to 90 K for t$$\approx $$ ≈ 1.2 nm. Our finding thus provides a practical guideline to achieve high crystallinity and low RR in ultra-thin SRO films by simply adjusting the growth of initial SrO layer.

Mechanical, Thermal and Electrical Characteristics of Conventionally Cast and Cold-Rolled 5754-Sc-Zr Aluminium Alloy

2019 ◽  
Vol 22 ◽  
pp. 55-64
Author(s):  
Martin Vlach ◽  
Veronika Kodetová ◽  
Hana Kudrnová ◽  
Michal Leibner ◽  
Marián Vlček ◽  
...  
Keyword(s):  
Cold Rolling ◽  
Electron Backscatter Diffraction ◽  
Residual Resistivity ◽  
Precipitation Process ◽  
Residual Resistivity Ratio ◽  
Scanning Calorimetry ◽  
Resistivity Ratio ◽  
Cold Rolled ◽  
Initial Difference ◽  
C 30

The effect of cold-rolling on mechanical, thermal, and electrical properties as well as microstructure behaviour of the Al-2.93wt.%Mg-0.34wt.%Mn-0.33wt.%Si-0.22wt.%Fe-0.19wt.%Cr-0.24wt.%Sc-0.06wt.%Zr was studied. The material was investigated during step-by-step isochronal annealing in a temperature range from room temperature up to 540 °C and during isothermal annealing at 200, 450 and 550 °C. Precipitation reactions were studied by electrical resistometry, conductivity, (micro) hardness measurements and differential scanning calorimetry. The hardening effect appears due to the additional precipitation of the Al3Sc and/or Al3(Sc,Zr) particles. The distinct changes in residual resistivity ratio above ~ 330 °C are probably caused by precipitation of the Mn (,Fe,Cr)-containing particles. This precipitation process is highly influenced by cold rolling but it has a negligible effect on hardness. The apparent activation energy values for additional formation of the Al3Sc and/or Al3(Sc,Zr) particles were determined. The kinetics of the Al3(Sc,Zr)-phase precipitation seems to be independent of Mn-and Mg-addition in the studied alloys. A partial recrystallization of the cold-rolled alloy was registered by electron backscatter diffraction after annealing at 550 °C. The initial difference in microhardness introduced by cold rolling is almost removed after annealing at 550 °C/30 min.

scholarly journals Variation of transition temperatures and residual resistivity ratio in vapor-grown FeSe

2016 ◽  
Vol 94 (2) ◽  
Author(s):  
A. E. Böhmer ◽  
V. Taufour ◽  
W. E. Straszheim ◽  
T. Wolf ◽  
P. C. Canfield
Keyword(s):  
Residual Resistivity ◽  
Transition Temperatures ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio

Electron channeling effect on highly oriented graphites–Size evaluation and oriented mapping of crystals

1992 ◽  
Vol 7 (6) ◽  
pp. 1400-1405 ◽  
Author(s):  
Akira Yoshida ◽  
Yoshihiro Hishiyama
Keyword(s):  
Room Temperature ◽  
Crystal Size ◽  
Pyrolytic Graphite ◽  
Residual Resistivity ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Axis Orientation ◽  
Electron Channeling ◽  
Channeling Effect ◽  
Size Evaluation

Structural studies on kish graphite (KG) and highly oriented pyrolytic graphite (HOPG) were performed using the techniques of electron channeling pattern (ECP) and electron channeling micrograph (ECM) in the scanning electron microscope. In the KG specimens the ECP for the single crystal was observed for each specimen, while in the HOPG specimens those of polycrystalline graphites with parallel c-axes were observed. The crystal sizes along the a-axis in the HOPG specimens were evaluated by ECM's. The average crystal size was related to a parameter sensitive to their crystallinity, i.e., the ratio of the resistivity at room temperature to that at 4.2 K (residual resistivity ratio). A mapping of the a-axis orientation of HOPG specimens was carried out.

HIGH QUALITY FULLY IN-SITU MgB2 THIN FILMS OBTAINED BY DC MAGNETRON SPUTTERING

2003 ◽  
Vol 17 (04n06) ◽  
pp. 779-784 ◽  
Author(s):  
M. G. MAGLIONE ◽  
F. CHIARELLA ◽  
R. DI CAPUA ◽  
R. VAGLIO ◽  
M. SALVATO ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
Magnetron Sputtering ◽  
Target Surface ◽  
Residual Resistivity ◽  
Precursor Film ◽  
Large Area ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio

MgB 2 thin films were grown in-situ at INFM- University of Naples by a magnetron sputtering technique in a UHV system (10-7 Pa) equipped with 3 focused 2′′ magnetron sources (a stoichiometric MgB 2 and metallic Mg and B targets by Superconducting Components Inc.). The substrates (sapphire or MgO) were placed "on axis" at 7 cm from the target surface on the surface of a molybdenum heater that could be operated up to 1000°C under vacuum. Best results were obtained codepositing MgB 2 and Mg at equal sputtering power (500W) for 10 min on cold substrates, resulting in a Mg rich Mg-B precursor film. The films were then annealed inhyphen;situ at 830°C for 10 min in a In sealed Nb box in presence of saturated Mg vapor. The process is highly reproducible and can be easily scaled to produce large area films. The resulting films were about 1μm thick, with 100nm surface roughness as measured by AFM Resistive transition showed a maximum T c of 35 K and a transition width lower than 0.5 K. The residual resistivity ratio was 1.6 for the best sample. Resistivity measurements in external magnetic field up to 8 T have been performed both in parallel and perpendicular configuration. The upper critical magnetic field vs. temperature behavior has been determined from the experimental data and the superconducting anisotropy has been calculated for samples with different T c .

scholarly journals Application of Copper Thermal Spraying for Electrical Joints between Superconducting Nb3Sn Cables

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 125
Author(s):  
Vincenzo D’Auria ◽  
Pierluigi Bruzzone ◽  
Mickael Sebastian Meyer ◽  
Enrique Rodriguez Castro ◽  
Stefano Sgobba
Keyword(s):  
Manufacturing Process ◽  
Superconducting Magnets ◽  
Thermal Spraying ◽  
Residual Resistivity ◽  
Operating Conditions ◽  
Contact Ratio ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Main Requirement ◽  
Globular Form

This manuscript reports on the application of copper thermal spraying in the manufacturing process of an electrical connection between Nb3Sn cables for superconducting magnets of fusion reactors. The joint is realized through diffusion bonding of the sprayed coating of the two cables. The main requirement for such a connection is its electrical resistance, which must be below 1 nΩ at B = 8 T, I = 63.3 kA and T = 4.5 K. Micrographs of the joint prototype were taken to relate the joint resistance with its microstructure and to provide feedback on the manufacturing process. Optical microscopy (OM) was used to evaluate the grain size of the coating, presence of oxide phases and to analyze the jointed surfaces. Scanning electron microscopy (SEM) and, in particular, energy-dispersive X-ray spectroscopy (EDX) were used to confirm the elemental composition of specimens extracted from the prototype. It is shown that the copper coating has an oxide concentration of 40%. Despite this, the resistance of the prototype is 0.48 nΩ in operating conditions, as the oxides are in globular form. The contact ratio between the jointed surfaces is about 95%. In addition, residual resistivity ratio (RRR) measurements were carried out to quantify the electrical quality of the Cu coating.

Large-Area <img src="/images/tex/812.gif" alt="\hbox {MgB}_{2}"> Films Fabricated by Scaled-Up Hybrid Physical–Chemical Vapor Deposition

2013 ◽  
Vol 23 (3) ◽  
pp. 7500304-7500304 ◽  
Author(s):  
Teng Tan ◽  
Chenggang Zhuang ◽  
Alex Krick ◽  
Ke Chen ◽  
X Xi
Keyword(s):  
Thin Films ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Film Surface ◽  
Chemical Vapor ◽  
Residual Resistivity ◽  
Large Area ◽  
Residual Resistivity Ratio ◽  
Resistivity Ratio ◽  
Physical Chemical

A scaled-up hybrid physical-chemical vapor deposition (HPCVD) method has been developed to fabricate large-area high-quality magnesium diboride (MgB2) thin films. The 2-in-diameter MgB2thin films on sapphire (0001) show uniform superconducting properties, includingTc~ 39 K, residual-resistivity ratio ~ 14, andJc(4.2 K) ~ 107A/cm2. X-ray diffraction showed that the films are epitaxial withc-axis normal to the film surface. The film properties are uniform across the 2-in substrate.

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