Plasma-Enhanced MOCVD of Superconducting Oxides

1993 ◽  
Vol 335 ◽  
Author(s):  
Kenji Ebihara ◽  
Tomoyuki Fujishima ◽  
Masanobu Shiga ◽  
Quanxi Jia
Keyword(s):  
Thin Films ◽  
Phase Reaction ◽  
Superconducting Transition ◽  
Superconducting Thin Film ◽  
High Tc ◽  
Rf Discharges ◽  
Excited Species ◽  
Thin Film Preparation ◽  
Plasma Enhancement ◽  
Source Materials

AbstractThe plasma-enhanced MOCVD is developed to prepare high-Tc oxide superconducting thin films. Plasmas generated by microwave and rf discharges decompose effectively the source materials ( β-diketonate chelates) into their elements and oxides. YBaCuO thin films were deposited on the MgO substrate of 500–650 °C at total pressure of 0.6–5 Torr with O2 contents less than 30%. The as-grown films produced by two kinds of plasma enhancement were porous and consisted of crystalline grains, but showed the superconducting transition after heating procedure at around 800 °C. It is shown that the inherent crystalline orientations of the as-grown films determine the crystal structure of the post-annealed films. The film of the metal atomic ratios of 0.91 for Ba/Y and 2.64 for Cu/Y showed the superconducting properties with Tc(zero) of 89 K and the critical current density (at 77 K) of 5×104 A/cm2. Spectroscopic analysis showed that the plasmas are composed of many excited species such as Y, Y+, Ba, Ba+, Cu, YO, BaO, CuO. Formation of the metal-oxides through the gas phase reaction is essential for the high-quality YBaCuO superconducting thin film preparation in the PEMOCVD.

Optimization of Jc for Photo-Assisted MOCVD Prepared YBCO Thin Films by Robust Design

1993 ◽  
Vol 335 ◽  
Author(s):  
P. C. Chou ◽  
Q. Zhong ◽  
Q. L. Li ◽  
A. Ignatiev ◽  
C. Y. Wang ◽  
...  
Keyword(s):  
Thin Films ◽  
Robust Design ◽  
Flow Rate ◽  
Chemical Vapor ◽  
Preparation Technique ◽  
Superconducting Thin Film ◽  
Variable Parameters ◽  
Ybco Thin Films ◽  
Thin Film Preparation ◽  
Phase Design

AbstractMetalorganic chemical vapor deposition (MOCVD) is emerging as a practical high Tc superconducting thin film preparation technique for industrial application. Intrinsically this technique involves a large number of variable parameters. This is especially critical for the quarternary or higher high Tc materials. Thus, effective methods are required to optimize the parameters for the preparation of high Tc films. A matrix experimental design named Robust Design has been employed for this purpose. The first-phase design was based on a starting knowledge of growth temperature and pressure, and annealing temperature for MOCVD preparation of YBCO thin films. A minimum lab effort of only nine deposition experiments was then used to optimize the process control parameters of precursor oven temperature, carrier gas (Ar) flow rate, O2 flow rate and N2O flow rate. The results were then followed by three confirmation depositions. The Robust Design resulted in the growth of YBCO film with Tc consistently in the range of 87.0 K to 90.2 K and Jc improved from about 1.0 × 106 A/cm2 to 3–5 × 106 A/cm2.

Preparation of SrRuO3 and CaRuO3 Films by Mocvd and its Application to Electrodes for Ferroelectric Thin Films

1999 ◽  
Vol 596 ◽  
Author(s):  
N Okuda ◽  
N Higashi ◽  
K Ishikawa ◽  
N Nukaga ◽  
H Funakubo
Keyword(s):  
Thin Films ◽  
Vapor Deposition ◽  
Metalorganic Chemical Vapor Deposition ◽  
Single Phase ◽  
Chemical Vapor ◽  
Crystal Perfection ◽  
Oriented Films ◽  
Thin Film Preparation ◽  
Film Preparation ◽  
Source Materials

AbstractSrRuO3 and CaRuO3 thin films were successfully prepared by metalorganic chemical vapor deposition (MOCVD). Sr(C11H19O2)2(C8H23N5)x – Ru(C11H19O2)3–O2 and Sr(C11H19O2)2(C8H23N5)x. – Ru[(C5H4)(C2H5)]2 - O2 systems, and Ca(C11H19O2)2(C8H23N5)x, – Ru(C11H19O2)3–O2 and Ca(C11 H19O2)2(C8H23N5)x – Ru[(C5H4)(C2H5)]2– O2 systems were used as source materials for SrRuO3 and CaRuO3 thin film preparation, respectively. Sr and Ca source vapors were successfully obtained by bubbling N2 gas including C8H23N5 vapor through liquid sources. Self-composition limiting to keep single phase of SrRuO3 and CaRuO3 was observed under an excess input of the Ru source at 700 – 750 °C for both Ru sources. Epitaxlly grown films with high crystal perfection were grown on various kinds of substrates in this temperature range. Epitaxially grown SrRuO3 film with three kinds of orientation, (100), (110) and (111), were deposited on (100), (110) and (111)SrTiO3 substrates, respectively. By using these films as bottom electrodes, we measured the ferroelectric anisotropy of SrBi2Ta2O9 by preparing (001)- and (116)- oriented films.

Observation by HVEM of the martensite transformation and the superconducting transition in Nb3Sn

1988 ◽  
Vol 46 ◽  
pp. 788-789
Author(s):  
M. A. Kirk ◽  
M. C. Baker ◽  
B. J. Kestel ◽  
H. W. Weber
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Superconducting State ◽  
Martensite Transformation ◽  
Sputter Deposition ◽  
Diffusion Reaction ◽  
Solute Diffusion ◽  
Superconducting Transition ◽  
Twin Boundaries ◽  
Martensite Structure

It is well known that a number of compound superconductors with the A15 structure undergo a martensite transformation when cooled to the superconducting state. Nb3Sn is one of those compounds that transforms, at least partially, from a cubic to tetragonal structure near 43 K. To our knowledge this transformation in Nb3Sn has not been studied by TEM. In fact, the only low temperature TEM study of an A15 material, V3Si, was performed by Goringe and Valdre over 20 years ago. They found the martensite structure in some foil areas at temperatures between 11 and 29 K, accompanied by faults that consisted of coherent twin boundaries on {110} planes. In pursuing our studies of irradiation defects in superconductors, we are the first to observe by TEM a similar martensite structure in Nb3Sn.Samples of Nb3Sn suitable for TEM studies have been produced by both a liquid solute diffusion reaction and by sputter deposition of thin films.

STUDY OF THE PREPARATION OF HIGH Tc SUPERCONDUCTING YBCO THIN FILMS BY A PLASMA-ASSISTED MOCVD PROCESS

1989 ◽  
Vol 50 (C5) ◽  
pp. C5-149-C5-153
Author(s):  
DING-KUN PENG ◽  
GUANG-YAO MENG ◽  
CHUN-BAO CAO ◽  
CHUN-LIN WANG ◽  
QI FANG ◽  
...  
Keyword(s):  
Thin Films ◽  
High Tc ◽  
Ybco Thin Films

scholarly journals Mechanistic Study on Facet-Dependent Deposition of Metal Nanoparticles on Decahedral-Shaped Anatase Titania Photocatalyst Particles

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 542 ◽  
Author(s):  
Kenta Kobayashi ◽  
Mai Takashima ◽  
Mai Takase ◽  
Bunsho Ohtani
Keyword(s):  
Mechanistic Study ◽  
Phase Reaction ◽  
Surface Charges ◽  
Platinum Nanoparticle ◽  
Nanoparticle Deposition ◽  
Selective Reaction ◽  
Anatase Titania ◽  
Deposition Density ◽  
Titania Photocatalyst ◽  
Source Materials

Facet-selective gold or platinum-nanoparticle deposition on decahedral-shaped anatase titania particles (DAPs) exposing {001} and {101} facets via photodeposition (PD) from metal-complex sources was reexamined using DAPs prepared with gas-phase reaction of titanium (IV) chloride and oxygen by quantitatively evaluating the area deposition density on {001} and {101} and comparing with the results of deposition from colloidal metal particles in the dark (CDD) or under photoirradiation (CDL). The observed facet selectivity, more or less {101} preferable, depended mainly on pH of the reaction suspensions and was almost non-selective at low pH regardless of the deposition method, PD or CDL, and the metal-source materials. Based on the results, the present authors propose that facet selectivity is attributable to surface charges (zeta potential) depending on the kind of facets, {001} and {101}, and pH of the reaction mixture and that this concept can explain the observed facet selectivity and possibly the reported facet selectivity without taking into account facet-selective reaction of photoexcited electrons and positive holes on {101} and {001} facets, respectively.

scholarly journals Strain-stabilized superconductivity

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
J. P. Ruf ◽  
H. Paik ◽  
N. J. Schreiber ◽  
H. P. Nair ◽  
L. Miao ◽  
...  
Keyword(s):  
Thin Films ◽  
Materials Science ◽  
Condensed Matter ◽  
Quantum States ◽  
Low Energy ◽  
Superconducting Transition ◽  
Superconducting Properties ◽  
Detailed Understanding ◽  
Epitaxial Strain ◽  
Promising Strategy

AbstractSuperconductivity is among the most fascinating and well-studied quantum states of matter. Despite over 100 years of research, a detailed understanding of how features of the normal-state electronic structure determine superconducting properties has remained elusive. For instance, the ability to deterministically enhance the superconducting transition temperature by design, rather than by serendipity, has been a long sought-after goal in condensed matter physics and materials science, but achieving this objective may require new tools, techniques and approaches. Here, we report the transmutation of a normal metal into a superconductor through the application of epitaxial strain. We demonstrate that synthesizing RuO2 thin films on (110)-oriented TiO2 substrates enhances the density of states near the Fermi level, which stabilizes superconductivity under strain, and suggests that a promising strategy to create new transition-metal superconductors is to apply judiciously chosen anisotropic strains that redistribute carriers within the low-energy manifold of d orbitals.

scholarly journals Preparation and Properties of Superconducting thin Films by Excimer Laser Ablation

1990 ◽  
Vol 191 ◽  
Author(s):  
Michael E. Geusic ◽  
Alan F. Stewart ◽  
Larry R. Pederson ◽  
William J. Weber ◽  
Kenneth R. Marken ◽  
...  
Keyword(s):  
Thin Films ◽  
Laser Ablation ◽  
Excimer Laser ◽  
Laser Energy ◽  
Substrate Surface ◽  
Xrd Analysis ◽  
Zero Field ◽  
Superconducting Transition ◽  
X Ray Diffraction ◽  
Excimer Laser Ablation

ABSTRACTExcimer laser ablation with an in situ heat treatment was used to prepare high quality superconducting YBa2Cu3O7−x thin films on (100)-SrTiO3 and (100)-LaAlO3 substrates. A pulsed excimer laser (XeCl; 308 nm) was used to ablate a rotating, bulk YBa2Cu3O7−x target at a laser energy density of 2–3 J/cm2. Based on four-probe dc resistance measurements, the films exhibited superconducting transition temperatures (Tc, midpoint) of 88 and 87K with 2K (90–10%) transition widths for SrTiO3 and LaAlO3, respectively. Transport critical current densities (Jc) measured at 77K were 2 × 106 and 1 × 106 A/cm2 in zero field for SrTiO3 and LaAlO3, respectively. X-ray diffraction (XRD) analysis showed the films to be highly oriented, with the c-axis perpendicular to the substrate surface.

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