Effects of Oxygen-Potential-Controlled Annealing on the Superconducting Properties of (Bi, Pb)2Sr2Ca2Cu3Oy Thin Films

Hattori, Hisao; Nakamura, Keikichi; Ogawa, Keiichi

doi:10.1143/jjap.29.l36

Cited by 26 publications

(3 citation statements)

References 11 publications

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“…It is known that the Tc of the BSCCO superconductor either increases or decreases with decreasing the oxygen content (12-17, 36, 37). This phenomenon may be explained because the BSCCO superconductor with an optimum value of oxygen content can obtain the optimum carrier concentration which corresponds to the maximum Tc (37)(38)(39). In this study, it is suggested that for the film annealed above 500~ in an oxygen-free atmosphere the decomposition of the 2212 phase as well as the change of the carrier concentration have strong relevance to the degradation of the Tc of the film.…”

Section: Resultsmentioning

confidence: 79%

Effect of Annealing Atmosphere on the Contact Resistivity, Superconductivity, and Phase Transformation in the Al / BiSrCaCuO System

Lin¹,

Kao²,

Fang³

et al. 1991

J. Electrochem. Soc.

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The contact resistivity, superconductivity, and phase transformation in the A1/BiSrCaCuO(BSCCO) system annealed in air, argon, and vacuum, respectively, were studied. The BSCCO films were deposited by dc sputtering on MgO substrates. For the A1/BSCCO films, capped with gold and annealed at 750~ in air, the contact resistivity of 7 x 10 .7 ~-cm 2 at 77 K can be obtained, whereas for the Al/BSCCO films annealed at above 500~ either in argon or in a vacuum of 6 x 10 .6 Torr, the contact resistivities show semiconducting behavior due to degraded superconductivity of the BSCCO film. During annealing in argon or a vacuum of 6 x 10 .6 Torr the melting temperatures of the 2212 phase are about 750 and 675~ respectively. These are considerably lower than that in air, 875-895~ The 2201 phase is the most stable phase in comparison with the 2212 and Bi2Sr2Ca~Cu30= phases during annealing in the oxygen-free atmosphere. The reversible change of the Tc of the BSCCO film has an intimate relationship with the decomposition and recrystallization of the 2212 phase, depending on the annealing atmosphere. Two of the decomposition products of the 2212 phase for the BSCCO film annealed in the oxygen-free atmosphere are identified to be 3-Bi203 and Cu20. In this study, the phase transformation and reversible change of the Tc for the BSCCO film annealed in various atmospheres can be explained in terms of the desorption and absorption of oxygen in the film.The discovery of high Tc superconductors (1, 2) has given a great impetus to applications of superconductors in many technical fields such as electronic devices, power transmission lines, and Josephson junctions. The essential requirement for these applications is the preparation of low-resistance electrical contacts to the superconductors. Numerous studies on silver and gold contacts to the superconductors have been performed (3-8). Aluminum is widely used in electronic devices, and it has been reported 5 that the substitution of aluminum into the BiSrCaCuO (BSCCO) system up to 20 atom percent (a/o) of the cations seems to have no significant effect on T~s (9-10). Therefore, 2.4 it is suggested that aluminum may be chosen for the electrode contacts on the BSCCO superc6nductor. Our previo 1.8 ous results have shown that for the Au/A1/BSCCO system W annealed in air a contact resistivity as low as 7 • 10 .7 ~-cm 2 can be obtained (11). However, in semiconductor processing technology, the aluminum contact is generally an-~ 1.2 0) nealed in an oxygen-free atmosphere to protect it from oxidation. Moreover, several authors have reported that for BSCCO samples annealed in various oxygen pressure the 0.6 Tc increases with decreasing oxygen content (12-17). Therefore, it is very interesting to study further the effect 0 of oxygen-free annealing on the AI/BSCCO contact system. In this study the contact resistivity, superconducting behavior, and the phase transformation of the A1]BSCCO and BSCCO films after annealing in argon and vacuum were studied and compared with the results obtained after anne...

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Section: Resultsmentioning

confidence: 79%

Effect of Annealing Atmosphere on the Contact Resistivity, Superconductivity, and Phase Transformation in the Al / BiSrCaCuO System

Lin¹,

Kao²,

Fang³

et al. 1991

J. Electrochem. Soc.

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“…[1] that it is only the La(2:l:4) system that truly follows the entire curve in both ascending and descending parts of the plateau. Rare-earth-based (1:2:3) and Bi-based 2122 compounds do not follow the curve in the range where p^ > 0.25 which is clear from the corresponding references, from where the pertinent data are taken [3,5]. In fact there are no experimental points available to substantiate the descending part of the plateau.…”

mentioning

confidence: 90%

“…It is characterized by a plateau, with sharp bends at both sides. The relation is primarily based on the experimental results [2][3][4][5][6][7][8] and is depicted in Fig. 1 of Ref.…”

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Comment on ‘‘Universal relationship betweenTcand the hole content inp-type cuprate superconductors’’

Awana

Narlikar

1993

Phys. Rev. Lett.

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Comment on "Universal Relationship between T c and the Hole Content in />-Type Cuprate Superconductors"In Ref.[1], Zhang and Sato have recently shown a universal relation to hold between T c and the hole content in high-r c cuprates. It is characterized by a plateau, with sharp bends at both sides. The relation is primarily based on the experimental results [2][3][4][5][6][7][8] and is depicted in Fig. 1 It is evident from Fig. 1 of Ref.[1] that it is only the La(2:l:4) system that truly follows the entire curve in both ascending and descending parts of the plateau. Rare-earth-based (1:2:3) and Bi-based 2122 compounds do not follow the curve in the range where p^ > 0.25 which is clear from the corresponding references, from where the pertinent data are taken [3,5]. In fact there are no experimental points available to substantiate the descending part of the plateau.In the case of Tl-based cuprates the above authors have considered the Tl 1212 where the data points have been depicted on both sides of the plateau. The hole concentration in this case is estimated by iodometric titration on the assumption of a fixed valence state of Tl 3+ . This we feel is incorrect and needs some discussion. In fact using the data of Ref.[9] the authors could well have similarly filled data points on both sides of the plateau for all Bibased cuprate systems also. We again feel this to be unjustified as the estimation of Cu valence in Ref.[9] is based on the iodometric titration on the assumption of a fixed 3 + valence state of Bi.Recently, there has been a weight of evidence that the valence states of Bi and Tl are less than 3+ [10-13] and can undergo variation, which has also been theoretically substantiated [14][15][16]. As a consequence of the simultaneous presence of two mixed valence cations, viz., Tl and Cu (or Bi and Cu), the task of estimating the copper valence, and hence the hole concentration, in both Tl-and Bi-based cuprates is seemingly an unsolved problem through the iodometric technique and, thus, the results yielded by the latter are not free from ambiguity. Moreover the T c of these systems is not only dependent on the number of holes in Cu, but is also controlled by the valence state of Bi and Tl [10-13].In the above background, the so-called universal relation presented in Ref.[1] is strictly valid, over the whole range of the plateau curve, only for the La(2:l:4) system [17], and the data presented for other systems remain far from conclusive in this respect. Clearly the problem of high T c in these materials is far more complicated. In cuprate systems with relatively large unit cells, such as those of Bi and Tl compounds formed with several stacks of cationic oxygen layers, the T c is controlled by interlayer coupling effects rather than by the carrier concentration alone, and as such it seems futile for us to expect any such universal relation existing between T c and carrier concentration.

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Effect of the oxygen pressure during annealing on T_c and lattice parameter c of Bi‐2212 single crystals

Vlasov

Kaminskaya

Moshkin

et al. 1994

Cryst. Res. Technol.

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Effects of Oxygen-Potential-Controlled Annealing on the Superconducting Properties of (Bi, Pb)₂Sr₂Ca₂Cu₃O_y Thin Films

Cited by 26 publications

References 11 publications

Effect of Annealing Atmosphere on the Contact Resistivity, Superconductivity, and Phase Transformation in the Al / BiSrCaCuO System

Effect of Annealing Atmosphere on the Contact Resistivity, Superconductivity, and Phase Transformation in the Al / BiSrCaCuO System

Comment on ‘‘Universal relationship betweenTcand the hole content inp-type cuprate superconductors’’

Effect of the oxygen pressure during annealing on T_c and lattice parameter c of Bi‐2212 single crystals

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Effects of Oxygen-Potential-Controlled Annealing on the Superconducting Properties of (Bi, Pb)2Sr2Ca2Cu3Oy Thin Films

Cited by 26 publications

References 11 publications

Effect of Annealing Atmosphere on the Contact Resistivity, Superconductivity, and Phase Transformation in the Al / BiSrCaCuO System

Effect of Annealing Atmosphere on the Contact Resistivity, Superconductivity, and Phase Transformation in the Al / BiSrCaCuO System

Comment on ‘‘Universal relationship betweenTcand the hole content inp-type cuprate superconductors’’

Effect of the oxygen pressure during annealing on Tc and lattice parameter c of Bi‐2212 single crystals

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Product

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Effects of Oxygen-Potential-Controlled Annealing on the Superconducting Properties of (Bi, Pb)₂Sr₂Ca₂Cu₃O_y Thin Films

Effect of the oxygen pressure during annealing on T_c and lattice parameter c of Bi‐2212 single crystals