Practical superconductor development for electrical power applications : annual report for FY 2001. Page: 20 of 88
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range of 100-300 mtorr) was obtained by flowing ultra-high-purity oxygen
through the chamber. A pulse repetition rate of 8 Hz produced a growth rate of
~15 nm/min. A CeO2 buffer layer (thickness ~10 nm) was deposited at 800 C by
PLD before depositing YBCO to improve the lattice match with YBCO.
The superconducting Tc and Jc were determined by the inductive method
and confirmed by the four-probe transport method at 77 K in liquid nitrogen.
The inductive test was used as a standard characterization tool to measure the
superconducting properties of our YBCO films. Thin-film superconductor
samples were placed between a primary and secondary coil pair with inner
diameter of 1 mm and outer diameter of 5 mm. Alternating current was
introduced to the primary coil and detected from the secondary coil by a lock-in
amplifier (Stanford Research Systems SR830 DSP). Samples used for transport
measurements were first coated with silver (thickness ~2 m) by e-beam
evaporation, then annealed for 2 h at 400 C in flowing high-purity oxygen.
Typical samples used for the four-probe transport measurement were 3-5 mm
wide and 1 cm long.
Texture was examined by X-ray diffraction pole figure analysis with Cu-Ka
radiation. In-plane texture was characterized by the FWHM of $-scans for the
YSZ (111) reflection (20 = 30.10), while out-of-plane texture was characterized by
the FWHM of w-scans for the YSZ (002) reflection (20 = 34.9 ). AFM observations
were conducted with a Digital Instruments D3100 SPM. TEM was done with a
Philips CM30 microscope operated at 300 keV.
The crystalline texture of the IBAD YSZ films was characterized by X-ray
diffraction pole figure analysis. A typical YSZ (111) X-ray pole figure is shown in
Fig. 10. Four well-defined (111) poles are evenly distributed with respect to the
azimuth angle and have a tilt (x-angle) of ~55. This confirmed that the (00!)
planes of the IBAD YSZ film are parallel to the substrate surface. Figures 11 and
12 show YSZ (111) $- and w-scans for ~1-[m YSZ films deposited on the HC
substrate, respectively. The FWHM of the YSZ (111) $-scan is usually used to
quantitatively characterize in-plane textures of IBAD YSZ films. Out-of-plane
texture was characterized from the YSZ (002) w-scan, shown in Fig. 12.
The IBAD YSZ films that were deposited with 300 eV beam energy at a substrate
temperature of 90 C gave an FWHM of 13.20 for the YSZ (111) $-scan and an
FWHM of 7.7 for the YSZ (200) w-scan.
Figure 13 plots the FWHM of a YSZ (111) $-scan vs. the substrate
temperature during deposition of ~1- m-thick IBAD YSZ films. In-plane texture
of the IBAD YSZ films improved with a decrease in substrate temperature.
These results suggest that a FWHM of ~12 could be obtained with a substrate
temperature of ~50 C.12
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Cha, Y. S.; Dorris, S. E.; Dusek, J. T.; Emerson, J. E.; Erck, R. A.; Fisher, B. L. et al. Practical superconductor development for electrical power applications : annual report for FY 2001., report, May 2, 2002; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc737902/m1/20/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.