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Artificial chessboard like textured YBCO films
Physica C 460–462 (2007) 766–767 www.elsevier.com/locate/physc
Artificial chessboard like textured YBCO films M.P. Lisitskiy a
a,*
, C. Camerlingo a, L. Gozzelino b, F. Laviano b, M. Russo
a
Consiglio Nazionale delle Ricerche, Istituto di Cibernetica ‘‘E. Caianiello’’, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy b Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy Available online 24 March 2007
Abstract A chessboard like structure of in-plane textured superconducting film with 4 · 4 lm2 elementary area has been fabricated by means of the homo-biepitaxial growing of YBCO film on yttria stabilized zirconia substrate. Regular arranged grain boundaries with fixed mismatch angle of 45 were realized. Each elemental square was connected to the four neighboring regions by p-Josephson junctions. Electro-physical properties of YBCO films with and without the chessboard like texture were measured. The magnetic field penetration into the chessboard like YBCO sample has been investigated by magneto-optical imaging at T = 4.2 K at different values of the applied magnetic field. The magneto-optical images have demonstrated the contribution of the grain-boundary superconducting transport to the formation of the magnetic field distribution inside the chessboard like sample. 2007 Elsevier B.V. All rights reserved. Keywords: Homo-biepitaxial YBCO film growth; High Tc Josephson junction; Magnetic field structure
1. Introduction The study of artificial thin film high Tc texture structures is important in order to understand the transport properties of natural granular high Tc films [1] and to carry out the experimental confirmation of d-wave pairing symmetry in cuprate superconducting materials [2]. In addition, artificial texture influences on the optical properties of high Tc thin films with potential implication in the field of terahertz application [3]. In the present paper, we report on results of experimental investigation of electro-physical and magnetic properties of chessboard like structure YBCO film realized by the homo-biepitaxial technique.
2. Sample fabrication The homo-biepitaxial growing is based on a 45 in-plane rotation of the grown YBCO films with respect to the substrate orientation realized by using a thin YBCO buffer *
Corresponding author. E-mail address: [email protected] (M.P. Lisitskiy).
0921-4534/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2007.03.076
layer deposited at a temperature (600 C) out of the superconducting phase condition and lower than the optimal value (800 C) [4]. Yttria-stabilized ZrO2 (YSZ) single crystal of (1 0 0) orientation was used as a substrate. YBCO films were deposited by dc magnetron sputtering with time modulated power as described in details in Ref. [5]. The first fabrication step was the deposition of an YBCO (600 C) buffer layer with a thickness of 20 nm. The buffer layer was patterned as chessboard like structure with 4 · 4 lm2 elementary area by means of UV photolithography process followed by a fast atom bombardment (FAB) in argon atmosphere. The second step was the deposition of YBCO (800 C) film with a thickness of 200 nm. The final chessboard textured YBCO film represented the system where each elemental square was connected to the four neighboring regions by p-Josephson junctions. The square shape sample of 2 · 2 mm2 was realized by photolithography process and FAB for electro-physical measurements. The square shape structure of 2 · 2 mm2 of YBCO (800 C) without buffer layer was fabricated as reference sample. At the end of the electro-physical tests, the chessboard like structures with square shapes of 50 · 50 lm2, 100 · 100 lm2, 150 · 150 lm2 and 200 · 200 lm2 were
M.P. Lisitskiy et al. / Physica C 460–462 (2007) 766–767
Fig. 1. Chessboard like YBCO structure of 200 · 200 lm2: (a) photograph of microscope image; (b) MO image registered at remnant state after application of a magnetic field of 180 mT. T = 4.2 K.
realized for magneto-optical imaging. Fig. 1a shows the photograph of microscope image of the chessboard like YBCO structure of 200 · 200 lm2. 3. Experimental results and discussion 3.1. Electro-physical measurements Four electrodes (one to each corner) were connected to the square shape samples of 2 · 2 mm2 with and without chessboard like texture. Voltage–current ratio for opposite pairs of electrodes was measured as a function of temperature (T) in order to evaluate both the temperature associated with a full superconducting transition ðT fc Þ and the resistivity at T = 200 K (q(200 K)) calculated by Montgomery method [6]. For each sample the measurements were done for two orthogonal sides. The chessboard like YBCO sample exhibited the complete superconducting transition at T fc ¼ 76:5 K. In the case of the bare YBCO film a slight difference between the resistivity for the two orthogonal sides was obtained (q1(200 K) = 3.2 mX cm, q2(200 K) = 2.7 mX cm), while the resistivity of chessboard like textured sample was of 1.3 mX cm for both orthogonal sides. 3.2. Magneto-optical analysis Magnetic properties of the chessboard like square YBCO structure of 200 · 200 lm2 were studied by the
767
quantitative magneto-optical (MO) analysis based on the optical Faraday effect [7]. The MO characterization of the magnetic field penetration into the sample was performed at T = 4.2 K. After cooling in zero magnetic field, a sequence of increasing magnetic field oriented perpendicular to the sample surface was applied. Fig. 1b reports the remnant state of the sample after application of maximum magnetic field of 180 mT. The chessboard pattern visualized in the optical analysis (see Fig. 1a) repeats itself in the magnetic field distribution. In particular, the MO measurement reveals that there are square shaped grains with strong supercurrent loops, surrounded by lower supercurrent paths. This result indicates that the magnetic field structure inside the chessboard like textured YBCO film depends on the grain-boundary superconducting transport capabilities as dictated by the homo-biepitaxial YBCO growth. As a conclusion, we developed the fabrication process for realization of large scale artificial textured YBCO structures. Electro-physical and MO measurements demonstrated that magnetic properties of such structures depend on the transport properties of grain-boundary between misoriented film regions. Acknowledgements This work is partially supported by MIUR under the project ‘‘Sviluppo di componentistica avanzata e sua applicazione a strumentazione biomedica’’ and under the project FIRB-RBAU01PYB3. References [1] E. Mezzetti, R. Gerbaldo, G. Ghigo, L. Gozzelino, B. Minetti, C. Camerlingo, A. Monaco, G. Cuttone, A. Rovelli, Phys. Rev. B 60 (1999) 7623. [2] C.C. Tsuei, J.R. Kirtley, Physica C 367 (2002) 1. [3] H.-T.S. Lihn, E.-J. Choi, S. Kaplan, H.D. Drew, Qi Li, D.B. Fenner, Phys. Rev. B 53 (1996) 927. [4] S.H. Tsai, C.C. Chi, M.K. Wu, Physica C 339 (2000) 155. [5] M.P. Lisitskiy, C. Camerlingo, M. Salvato, A. Vecchione, M. Russo, J. Phys.: Conf. Series 43 (2006) 1135. [6] H.C. Montgomery, J. Appl. Phys. 42 (1971) 2971. [7] F. Laviano, D. Botta, A. Chiodoni, R. Gerbaldo, G. Ghigo, L. Gozzelino, S. Zannella, E. Mezzetti, Supercond. Sci. Technol. 16 (2003) 71.
Artificial chessboard like textured YBCO films M.P. Lisitskiy a
a,*
, C. Camerlingo a, L. Gozzelino b, F. Laviano b, M. Russo
a
Consiglio Nazionale delle Ricerche, Istituto di Cibernetica ‘‘E. Caianiello’’, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy b Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy Available online 24 March 2007
Abstract A chessboard like structure of in-plane textured superconducting film with 4 · 4 lm2 elementary area has been fabricated by means of the homo-biepitaxial growing of YBCO film on yttria stabilized zirconia substrate. Regular arranged grain boundaries with fixed mismatch angle of 45 were realized. Each elemental square was connected to the four neighboring regions by p-Josephson junctions. Electro-physical properties of YBCO films with and without the chessboard like texture were measured. The magnetic field penetration into the chessboard like YBCO sample has been investigated by magneto-optical imaging at T = 4.2 K at different values of the applied magnetic field. The magneto-optical images have demonstrated the contribution of the grain-boundary superconducting transport to the formation of the magnetic field distribution inside the chessboard like sample. 2007 Elsevier B.V. All rights reserved. Keywords: Homo-biepitaxial YBCO film growth; High Tc Josephson junction; Magnetic field structure
1. Introduction The study of artificial thin film high Tc texture structures is important in order to understand the transport properties of natural granular high Tc films [1] and to carry out the experimental confirmation of d-wave pairing symmetry in cuprate superconducting materials [2]. In addition, artificial texture influences on the optical properties of high Tc thin films with potential implication in the field of terahertz application [3]. In the present paper, we report on results of experimental investigation of electro-physical and magnetic properties of chessboard like structure YBCO film realized by the homo-biepitaxial technique.
2. Sample fabrication The homo-biepitaxial growing is based on a 45 in-plane rotation of the grown YBCO films with respect to the substrate orientation realized by using a thin YBCO buffer *
Corresponding author. E-mail address: [email protected] (M.P. Lisitskiy).
0921-4534/$ - see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.physc.2007.03.076
layer deposited at a temperature (600 C) out of the superconducting phase condition and lower than the optimal value (800 C) [4]. Yttria-stabilized ZrO2 (YSZ) single crystal of (1 0 0) orientation was used as a substrate. YBCO films were deposited by dc magnetron sputtering with time modulated power as described in details in Ref. [5]. The first fabrication step was the deposition of an YBCO (600 C) buffer layer with a thickness of 20 nm. The buffer layer was patterned as chessboard like structure with 4 · 4 lm2 elementary area by means of UV photolithography process followed by a fast atom bombardment (FAB) in argon atmosphere. The second step was the deposition of YBCO (800 C) film with a thickness of 200 nm. The final chessboard textured YBCO film represented the system where each elemental square was connected to the four neighboring regions by p-Josephson junctions. The square shape sample of 2 · 2 mm2 was realized by photolithography process and FAB for electro-physical measurements. The square shape structure of 2 · 2 mm2 of YBCO (800 C) without buffer layer was fabricated as reference sample. At the end of the electro-physical tests, the chessboard like structures with square shapes of 50 · 50 lm2, 100 · 100 lm2, 150 · 150 lm2 and 200 · 200 lm2 were
M.P. Lisitskiy et al. / Physica C 460–462 (2007) 766–767
Fig. 1. Chessboard like YBCO structure of 200 · 200 lm2: (a) photograph of microscope image; (b) MO image registered at remnant state after application of a magnetic field of 180 mT. T = 4.2 K.
realized for magneto-optical imaging. Fig. 1a shows the photograph of microscope image of the chessboard like YBCO structure of 200 · 200 lm2. 3. Experimental results and discussion 3.1. Electro-physical measurements Four electrodes (one to each corner) were connected to the square shape samples of 2 · 2 mm2 with and without chessboard like texture. Voltage–current ratio for opposite pairs of electrodes was measured as a function of temperature (T) in order to evaluate both the temperature associated with a full superconducting transition ðT fc Þ and the resistivity at T = 200 K (q(200 K)) calculated by Montgomery method [6]. For each sample the measurements were done for two orthogonal sides. The chessboard like YBCO sample exhibited the complete superconducting transition at T fc ¼ 76:5 K. In the case of the bare YBCO film a slight difference between the resistivity for the two orthogonal sides was obtained (q1(200 K) = 3.2 mX cm, q2(200 K) = 2.7 mX cm), while the resistivity of chessboard like textured sample was of 1.3 mX cm for both orthogonal sides. 3.2. Magneto-optical analysis Magnetic properties of the chessboard like square YBCO structure of 200 · 200 lm2 were studied by the
767
quantitative magneto-optical (MO) analysis based on the optical Faraday effect [7]. The MO characterization of the magnetic field penetration into the sample was performed at T = 4.2 K. After cooling in zero magnetic field, a sequence of increasing magnetic field oriented perpendicular to the sample surface was applied. Fig. 1b reports the remnant state of the sample after application of maximum magnetic field of 180 mT. The chessboard pattern visualized in the optical analysis (see Fig. 1a) repeats itself in the magnetic field distribution. In particular, the MO measurement reveals that there are square shaped grains with strong supercurrent loops, surrounded by lower supercurrent paths. This result indicates that the magnetic field structure inside the chessboard like textured YBCO film depends on the grain-boundary superconducting transport capabilities as dictated by the homo-biepitaxial YBCO growth. As a conclusion, we developed the fabrication process for realization of large scale artificial textured YBCO structures. Electro-physical and MO measurements demonstrated that magnetic properties of such structures depend on the transport properties of grain-boundary between misoriented film regions. Acknowledgements This work is partially supported by MIUR under the project ‘‘Sviluppo di componentistica avanzata e sua applicazione a strumentazione biomedica’’ and under the project FIRB-RBAU01PYB3. References [1] E. Mezzetti, R. Gerbaldo, G. Ghigo, L. Gozzelino, B. Minetti, C. Camerlingo, A. Monaco, G. Cuttone, A. Rovelli, Phys. Rev. B 60 (1999) 7623. [2] C.C. Tsuei, J.R. Kirtley, Physica C 367 (2002) 1. [3] H.-T.S. Lihn, E.-J. Choi, S. Kaplan, H.D. Drew, Qi Li, D.B. Fenner, Phys. Rev. B 53 (1996) 927. [4] S.H. Tsai, C.C. Chi, M.K. Wu, Physica C 339 (2000) 155. [5] M.P. Lisitskiy, C. Camerlingo, M. Salvato, A. Vecchione, M. Russo, J. Phys.: Conf. Series 43 (2006) 1135. [6] H.C. Montgomery, J. Appl. Phys. 42 (1971) 2971. [7] F. Laviano, D. Botta, A. Chiodoni, R. Gerbaldo, G. Ghigo, L. Gozzelino, S. Zannella, E. Mezzetti, Supercond. Sci. Technol. 16 (2003) 71.