Three - University of Arkansas Physics Department

Enhancement of Critical Cumnt Density in 'llzBa~aCu20, Superconducting thin Film
On Polycrystalline A1203 Substrates Using Textured YSZ Buffer Layers
Q. Xiong, S. Afonso, K. Y. Chen, G. Salamo, and F. T. Chan
Department of Physics /High Density Electronics Center, University of Arkansas,
Fayetteville, AR 72701 ,USA.
TlzBa~CaCu20, superconducting thin films on plycrystalline Alfi substrates with and without textured @riastabilized-zirconiawSZ)
or CcqNSZ buffer layers were fabricated Ion beam-assisted laser deposition was used
to obain the textured YSZ Mer layers. The TI2Ba2CaCuZqr thin films grown on the YSZ buffer layers were
highly c-axis oriented with respect to the film surface and svongly in plane textured. The zero resistance
temprature of these films was 100-108K. The critical cumnt density (J,) of he films grown on the YSZ buffer
layers was 10' A/cm2. Jc of the films grown on the Q0-J YSZ buffer layer or on A12Q substrates dimly was less
than lo4 A/cmZ.
1. INTRODUCTION 2. EXPERIMENTS
TI2212 films with a higher T, and lower surface
resistance than YBCO have attraded some attention.
Due to the high volatility and chemical reactivity of
thallium at high temperature, thallium related thin
films ue much more difficult to fabricate than
YBCO thin films. As a nsult, high quality thin
films of Tl2212 with 1,'s of up to about lo6 A/cm2
and Tc's of up to about 105K have only been pwn
on single crystal L~.AIG[" or sfliGtZ1 substrates.
With a bu&r layer be(ween Tl2212 and single
crystal substrates other than single crystal LaW& or
SrTi4, the highest Tc and J, IM1 so far has been
-98K and -3x 1d A/cm2 rtspactivtly. Many studies
have shown tbat using ion beam-askted laser
high @v m2cu3oy
WCO)'" films can be deposited on bhxially
aligned YSZ layers grown on noneline
subbbates with J,'s up to 8~10~A/cm~ at 75K. Them
are very few reports of TI-related films which were
grown 00 ~]n-e aysral subsbates using IBAD
method. Using BAD method to shrdy TI-2212 fiIm
grownonwo-singlecrystalsubsvateswithdifferurt
texture4 bu&r Layas may offkr a new a m h for
producing inexpensive Tl-related films with high Tc
and Jc ciwaue&i~. Here, we report the results of
J, of TU2 12 film grown on A110, substrates directly,
on YSZI Alfi and on W S Z / Alfi.
Ion-beam assisted pllsed laser deposrtion was used
to prepare highly baxial aligned YSZ films on
polycrystalline Alfi substrates at room temperature.
Next a CeQ layer was deposited on the YSZl A124.
The M s of the process have been reported
e ~ '. In short, d while YSZ was depos~ted by
pulse laser deposition, an ion-beam (argon ion
source) was used to bomberd the &strates at an
angle of 55' from the substrate normal. The
thickness of the YSZ buffer Laytrs in our experiment
were abwt 5000 A. AAcr dcposlting YSZ buffer
layers a CeQ layer about 4000A were deposited on
YSZ as a secoed Mer layer for some of YSZ/A124.
The 2000-3000A Ba2CaCuZqr precursor films were
@oared on Alfi sukstrates on YSZIAlfi, and on
WNSZI Alfi qarately at a temperature of
400°C using pulsed laser ablation. In order to
optimize synthesis conditions, the films with bulk
TI2212 were heated to about 800°C and held at this
temperature for abwt 8 hours at various oxygen
partla1 pressures for formation of TI2212 phase.
Finally, they were annealed at differing temperatures
and oxygen partial pressures.
3. RESULTS
All YSZ films dtposlted on plycrystalline
Al2q substrates were (001) oriented with the
axis normal tothe substra(e plane. The full wictth at
09214534197/$17.00 O Elsevier Science B.V. All rights reserved.
PI1 S09214534(97)00459-0