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Microwave properties of Halide-CVD grown BiSrCaCuO thin films
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Physica C 185-189 (1991) 2021-2022 North-Holland
Microwave Propertiesof Halide-CVD Grown BiSrCaCuO Thin Films T. Nakamura, C. Yoshicla, H. Yamawaki, and M. lhara Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi 243-01, Japan
We have studied the surface resistance (Rs) at 9.6GHz of CVD ~ w n BiS~aCuO thin films. Rs v a l ~ as low as 0.2m~ at 60K could be attained in films whose grain sizes are as large as 30ktm. The firms which consi~ of small grains (<0.Spin) showed a dependence of Rs on the rotational misalignments of ~ i n s . In highly ~ n t e d films. Rs is about 0.6mf~ at 4K which is less than one third of that of rotationaly misaligned film. 1. INTRODUCTION
axis orientations, nondestructive!y 6. ~ t i c a l tempe~tures
The possibility of applying high Tc superconductors to
(Tc) and critical current densities (Jc) of all the ~mples
microwave devices has stimulated great interest in the
were Tc = 75 to 80 K and Jc = ! x l ~ to 1 x l ~ A/cm2 m
surface resistance (Rs) of the thin films 1. Improved
50 K. The Rs of the BSCCO thin films ~
processing methodes have already led to considerable
a cavity perturbation technique in a 9.6 GHz, T E 0 1 1 - ~
reduction in the Rs of thin films, especially for Y-Ba-Cu-O
superconducting cavity 7,8. The samples ( I c m x I cm) were
thin films. There are, however, few reports on the
supported on top of a sapphire rod at the ~ t r i c
microwave properties of the Bi-Sr-Ca-Cu-O (BSCCO)
the cavity and parallel to the caviiy axis. The surface
superconductors !-3 and the Rs data for polycrystalline
magnetic field at the superconducting sm'np!e is estimated to
BSCCO samples shows fairly high residual losses. We
be approximetly 0.01 gauss.
~ ~
t,~ng
center
have previously demonstrated the successful growth of BSCCO films on (001) MgO substrates by chemical vapor
3. RESULTS AND DISCUSSION
(CVD) 4. In this paper we report on the
We used three types of BSCCO films (~ype-A, -B, and -
temperature dependent Rs for the BSCCO films which
C). Figure 1 shows a POM photograph of the rype-C films
deposition
consist of grains of different sizes and with different a-axis
in the transmission mode. ~ e
orientations, to clarify the effect of the grain-boundaries on
diagonal position under the crossed nicoles condition. We
sample was set at the
the losses. 2. EXPERIMENTAL High-quality BSCCO films with a thickness of 250 to 350 nm were
prepared
using
halide
open-tube
CVD
techniques4, 5. In this growth system, BiC13, Srl2, Cal2, CuBr2, and 02 were used as source
. . . .
-~: -
l-
tnatcxttu~,
A I1
t-xn
of .u.~,,,.
films were grown on (001) MgO substrates at about 775°C. X-ray diffraction showed that all the films are oriented with their c-axis perpendicular to the MgO (001) plane and consist of high-Tc (I 10K) and low-Tc (80K) phases. We used a polarizing optical microscope (POM) with a tilting compensator in the normal reflection mode or the transmission mode to determine the grain sizes and the a-
Figure 1 A pol~-izing microscope photog'raph of BSCCO thin fi~m with large grains (q,'pe-C).
0921-4534D1/$03.50 O 1991 - Elsevier Science Publishers B.V. All rights reserved.
Z Nakamura et al. / Microwave propeaies of halide-CVD grown BiSrCaCuO thin films
2022
can say that type-C films consist of large grains with
with their c-axis perpendicular to the MgO (001) plane, the
dimensions of >30pro, whose a-axes are aligned with the MgO [1(30] or [010] directions.Similar POM observations
Rs difference between the type A- and B films is due to the difference of the a- and b-axis orientation. Therefore, we
show that type-A films consist of small grains with
can say that the Rs of the BSCCO films strongly depends
dimensions of <0.5pm, whose a-axes are aligned with the
not only on the density of the grain-boundaries but on the
MgO [100] axis. Type-B films also consist of small grains
rotational misalignment of the grains.
with dimensions of <0.5pm, but the a-axes are not aligned with the MgO <100> axis so that the grain-boundaries could
4. CONCLUSIONS
not be distinguished by the POM observation. Figure 2 shows the temperature dependence of the Rs at
The 9.6 GHz surface resistance (Rs) of the CVD grown Bi-Sr-Ca-Cu-O films strongly depends not only on the
9.6GHz for the three types of samples. The large grain sample (type-C) shows Rs as low as 0.2m~ at a
density of the grain boundaries but on the orientational alignment. Rs-values as low as 0.2m~ at 60K, which is
temperature between 10 and 60K which is about 50 times
about 50 times lower than the Rs of Cu could be attained in
lower than the Rs of Cu at the same frequency and
films whose grain size are as large as 30gin. Films
temperature. The limitation on sensitivity in this 9.6GHz
consisting of small grains, that is, containing a high density
measurement is =0.2m~8, 9 so that the actual surface
of grain boundaries showed a dependence of Rs on the
resistance is below our sensitiviy limit. The gradual
rotational misalignments of grains. Highly a-axis oriented
decrease of Rs from 110K to 60K seemes to be due to the
films had a Rs-value of about 0.6mf~ at 4K which is less
mixed phase feature of our films (80 and 110K-phases). The small grain samples (type-A and -B) show a broader Rs
than one third of that of the rotationaly misaligned film.
transition between 4 and 80K and the Rs at 70K is about
REFERENCES
two orders of magnitude higher than that of the type-C sample. This means that the temperature dependent Rs in the type-A and -B films is attributed to the grainboundaries. The type-A films show a Rs-value which is less than one third of that of the type-B films in spite of similar grain sizes. Since all the films are highly oriented
1 0° A
¢b
a
z.,...
m10-1
iA
A A
A
........... ~ ....... ¢ ............. ~.......... i - ............................ •.........................
o" U)
A
z_
• 10 fD,,,
-2
I::
...........
i
J, A A
,,,¢
010-a
............ i , .
~ •
i
...........
i~,
i
........................... : ..........................
*i
.-. .............. .a....0. .......................... j.....................................
~o®_
H. Piel and G. Miiller, IEEE Trans. Magn. MAG-27, 854(1991) and references therein. . G. Miiller, D.J. Brauer, R. Eujen, M. Hein, N. Klein, H. Piel, L. Ponto, U. Klein, and M. Peinger, IEEE Trans. Magn. MAG-25, 2402(1989). C.L. Bohn, J.R. Delayen, U. Balachandran, and M.T.Lanagan, Appl. Phys. Lett. 55, 304(1989). . M. Ihara, T. Kimura, H. Yamawaki, and K. Ikeda, IEEE. Trans. Magn. MAG-25, 2470(1989). . M.Ihara, H. Nakao, H. Yamawaki, and T. Kimura, contr, to this conf.. . T.Nakamura, C. Yoshida, T. Kimura, M. Ihara, and O. Ueda, to be published. . The Rs measurements were perfomed in Superconductor Technolo~es Inc.
i
1 0 "4
O 20 40 60 80 1 0 0 1 2 0 1 4 0 1 6 0 Temperature(K) Figure 2 The temperature dependence of the Rs at 9.6GHz for the three types of films (type-A, B, and C).
. L. D. Chang, M. J. Moskowitz, R. B. Hammond, M. M. Eddy, W. L. Olson, D. D. Casavant, E. J. Smith, M. Robinson, L. Drabeck, and G. Gruner, Appl. Phys. Lett. 55, 1357(1989). 9. J. Bybokas at STI, priv. comm..
Physica C 185-189 (1991) 2021-2022 North-Holland
Microwave Propertiesof Halide-CVD Grown BiSrCaCuO Thin Films T. Nakamura, C. Yoshicla, H. Yamawaki, and M. lhara Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi 243-01, Japan
We have studied the surface resistance (Rs) at 9.6GHz of CVD ~ w n BiS~aCuO thin films. Rs v a l ~ as low as 0.2m~ at 60K could be attained in films whose grain sizes are as large as 30ktm. The firms which consi~ of small grains (<0.Spin) showed a dependence of Rs on the rotational misalignments of ~ i n s . In highly ~ n t e d films. Rs is about 0.6mf~ at 4K which is less than one third of that of rotationaly misaligned film. 1. INTRODUCTION
axis orientations, nondestructive!y 6. ~ t i c a l tempe~tures
The possibility of applying high Tc superconductors to
(Tc) and critical current densities (Jc) of all the ~mples
microwave devices has stimulated great interest in the
were Tc = 75 to 80 K and Jc = ! x l ~ to 1 x l ~ A/cm2 m
surface resistance (Rs) of the thin films 1. Improved
50 K. The Rs of the BSCCO thin films ~
processing methodes have already led to considerable
a cavity perturbation technique in a 9.6 GHz, T E 0 1 1 - ~
reduction in the Rs of thin films, especially for Y-Ba-Cu-O
superconducting cavity 7,8. The samples ( I c m x I cm) were
thin films. There are, however, few reports on the
supported on top of a sapphire rod at the ~ t r i c
microwave properties of the Bi-Sr-Ca-Cu-O (BSCCO)
the cavity and parallel to the caviiy axis. The surface
superconductors !-3 and the Rs data for polycrystalline
magnetic field at the superconducting sm'np!e is estimated to
BSCCO samples shows fairly high residual losses. We
be approximetly 0.01 gauss.
~ ~
t,~ng
center
have previously demonstrated the successful growth of BSCCO films on (001) MgO substrates by chemical vapor
3. RESULTS AND DISCUSSION
(CVD) 4. In this paper we report on the
We used three types of BSCCO films (~ype-A, -B, and -
temperature dependent Rs for the BSCCO films which
C). Figure 1 shows a POM photograph of the rype-C films
deposition
consist of grains of different sizes and with different a-axis
in the transmission mode. ~ e
orientations, to clarify the effect of the grain-boundaries on
diagonal position under the crossed nicoles condition. We
sample was set at the
the losses. 2. EXPERIMENTAL High-quality BSCCO films with a thickness of 250 to 350 nm were
prepared
using
halide
open-tube
CVD
techniques4, 5. In this growth system, BiC13, Srl2, Cal2, CuBr2, and 02 were used as source
. . . .
-~: -
l-
tnatcxttu~,
A I1
t-xn
of .u.~,,,.
films were grown on (001) MgO substrates at about 775°C. X-ray diffraction showed that all the films are oriented with their c-axis perpendicular to the MgO (001) plane and consist of high-Tc (I 10K) and low-Tc (80K) phases. We used a polarizing optical microscope (POM) with a tilting compensator in the normal reflection mode or the transmission mode to determine the grain sizes and the a-
Figure 1 A pol~-izing microscope photog'raph of BSCCO thin fi~m with large grains (q,'pe-C).
0921-4534D1/$03.50 O 1991 - Elsevier Science Publishers B.V. All rights reserved.
Z Nakamura et al. / Microwave propeaies of halide-CVD grown BiSrCaCuO thin films
2022
can say that type-C films consist of large grains with
with their c-axis perpendicular to the MgO (001) plane, the
dimensions of >30pro, whose a-axes are aligned with the MgO [1(30] or [010] directions.Similar POM observations
Rs difference between the type A- and B films is due to the difference of the a- and b-axis orientation. Therefore, we
show that type-A films consist of small grains with
can say that the Rs of the BSCCO films strongly depends
dimensions of <0.5pm, whose a-axes are aligned with the
not only on the density of the grain-boundaries but on the
MgO [100] axis. Type-B films also consist of small grains
rotational misalignment of the grains.
with dimensions of <0.5pm, but the a-axes are not aligned with the MgO <100> axis so that the grain-boundaries could
4. CONCLUSIONS
not be distinguished by the POM observation. Figure 2 shows the temperature dependence of the Rs at
The 9.6 GHz surface resistance (Rs) of the CVD grown Bi-Sr-Ca-Cu-O films strongly depends not only on the
9.6GHz for the three types of samples. The large grain sample (type-C) shows Rs as low as 0.2m~ at a
density of the grain boundaries but on the orientational alignment. Rs-values as low as 0.2m~ at 60K, which is
temperature between 10 and 60K which is about 50 times
about 50 times lower than the Rs of Cu could be attained in
lower than the Rs of Cu at the same frequency and
films whose grain size are as large as 30gin. Films
temperature. The limitation on sensitivity in this 9.6GHz
consisting of small grains, that is, containing a high density
measurement is =0.2m~8, 9 so that the actual surface
of grain boundaries showed a dependence of Rs on the
resistance is below our sensitiviy limit. The gradual
rotational misalignments of grains. Highly a-axis oriented
decrease of Rs from 110K to 60K seemes to be due to the
films had a Rs-value of about 0.6mf~ at 4K which is less
mixed phase feature of our films (80 and 110K-phases). The small grain samples (type-A and -B) show a broader Rs
than one third of that of the rotationaly misaligned film.
transition between 4 and 80K and the Rs at 70K is about
REFERENCES
two orders of magnitude higher than that of the type-C sample. This means that the temperature dependent Rs in the type-A and -B films is attributed to the grainboundaries. The type-A films show a Rs-value which is less than one third of that of the type-B films in spite of similar grain sizes. Since all the films are highly oriented
1 0° A
¢b
a
z.,...
m10-1
iA
A A
A
........... ~ ....... ¢ ............. ~.......... i - ............................ •.........................
o" U)
A
z_
• 10 fD,,,
-2
I::
...........
i
J, A A
,,,¢
010-a
............ i , .
~ •
i
...........
i~,
i
........................... : ..........................
*i
.-. .............. .a....0. .......................... j.....................................
~o®_
H. Piel and G. Miiller, IEEE Trans. Magn. MAG-27, 854(1991) and references therein. . G. Miiller, D.J. Brauer, R. Eujen, M. Hein, N. Klein, H. Piel, L. Ponto, U. Klein, and M. Peinger, IEEE Trans. Magn. MAG-25, 2402(1989). C.L. Bohn, J.R. Delayen, U. Balachandran, and M.T.Lanagan, Appl. Phys. Lett. 55, 304(1989). . M. Ihara, T. Kimura, H. Yamawaki, and K. Ikeda, IEEE. Trans. Magn. MAG-25, 2470(1989). . M.Ihara, H. Nakao, H. Yamawaki, and T. Kimura, contr, to this conf.. . T.Nakamura, C. Yoshida, T. Kimura, M. Ihara, and O. Ueda, to be published. . The Rs measurements were perfomed in Superconductor Technolo~es Inc.
i
1 0 "4
O 20 40 60 80 1 0 0 1 2 0 1 4 0 1 6 0 Temperature(K) Figure 2 The temperature dependence of the Rs at 9.6GHz for the three types of films (type-A, B, and C).
. L. D. Chang, M. J. Moskowitz, R. B. Hammond, M. M. Eddy, W. L. Olson, D. D. Casavant, E. J. Smith, M. Robinson, L. Drabeck, and G. Gruner, Appl. Phys. Lett. 55, 1357(1989). 9. J. Bybokas at STI, priv. comm..