Preparation of Tl-Ba-Ca-Cu-O thin films by diffusion of Tl into laser evaporated Ba2Ca2Cu3Ox films

Lengfellner, Hans; Betz, J.; Renk, K. F.

doi:10.1007/bf00619726

Cited by 12 publications

(4 citation statements)

References 7 publications

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“…We find Tc values for the resistive transition of 100 K -115 K (10%-90%) and T fl=° ,,, 98 K. Towards high temperatures the resistivity increases almost linearly. The slope of the resistivity including the Tc values is very similar to films produced by the Nd:YAG laser ablation technique [6]. To compare the surface quality of Nd:YAG-and excimer laser produced films we made surface profile scans with a stylus equipment (a-step).…”

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confidence: 88%

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Superconducting Tl Ca Ba Cu O thin films prepared by diffusion of Tl into an excimer laser ablated Ca 2 Ba 2 Cu 3 O x film

Betz

Lengfellner

Duschl

et al. 1989

Physica C: Superconductivity and its Applications

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By laser ablation with an excimer laser (308 nm) cuprate films from a Ca2Ba2CuaOz sintered bulk target were deposited onto SrTiO3 (100) single crystal substrates. Thallium was added by a diffusion process by simultaneously annealing of the cuprate films together with a sintered T12Ca2Ba2Cua01o bulk sample both enclosed in a covered metal box; this film production method allowed to reduce the contamination by thallium. Scanning electron micrographs of the film surface show crystalline structures, i.e. a network of needle shaped crystallites laying in the film plane. For comparison, Nd:YAG laser produced films show rough surfaces consisting of clusters of grains.Thin films of T1-Ca-Ba-Cu-O compounds have been produced by several groups using electron beam evaporation [1] and sputtering techniques [2][3][4]. The use of thallium leads, however, to contamination of the film deposition system. This has been partially avoided by a film preparation procedure [5]: First, a Ca-Ba-Cu-O film was prepared by sputtering, then, by a heat treatment, thallium was diffused into the film from a metallic piece of thallium. Films with T~ =° values of 75 K were obtained by this technique [5]. We have recently developed a technique [6] where thallium was brought into the film by a diffusion technique, too; a Nd:YAG laser was used for preparation of the Ca-Ba-Cu-O film. In the work described here we have used an excimer laser, thus reaching a largely improved film quality.The film deposition system [7] consisted of a vacuum chamber with a base pressure of 5 x 10 -8 Torr. The excimer laser beam (308 nm, pulse duration 40 ns, pulse energy 450 m J) was directed by a quartz optic into the vacuum chamber and focused onto a rotating Ca2Ba2CuaOx sintered bulk target. The energy density on the target was about 10 J/cm 2. The SrTiO3 (100) single crystal substrates were heated to 400°C during the deposition procedure. To obtain structurized films a mask could be aligned in front of the substrate. Bridgelike structures could be easily obtained and were used for bolometric applications in optical response measurements.In the next preparation step the film was loaded with thallium by a diffusion procedure: A standard 0921-4534/89/$03.50 © Elsevier Science Publishers B.V. (North-Holland) Tl2Ca2Ba2CuaOao bulk sample was placed upon the film, a stainless steel ring was used as a spacer between film and bulk sample. The whole arrangement was placed into a small covered stainless steel box, and was heated for about 5 min in a preheated furnace to 880°C, then taken off and cooled to room temperature.

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confidence: 88%

“…Films with T~ =° values of 75 K were obtained by this technique [5]. We have recently developed a technique [6] where thallium was brought into the film by a diffusion technique, too; a Nd:YAG laser was used for preparation of the Ca-Ba-Cu-O film. In the work described here we have used an excimer laser, thus reaching a largely improved film quality.…”

mentioning

confidence: 99%

Superconducting Tl Ca Ba Cu O thin films prepared by diffusion of Tl into an excimer laser ablated Ca 2 Ba 2 Cu 3 O x film

Betz

Lengfellner

Duschl

et al. 1989

Physica C: Superconductivity and its Applications

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“…The measurements were carried out on polycrystalline T1-BaCa-Cu-O superconducting films of about l#m thickness showing transition temperatures near 100 K. The film preparation procedures and details on the morphology of the films were described elsewhere [6,7]. The films were deposited on 10 • 10 x 1 mm 3 SrTiO3 substrates and had bridge-like patterns.…”

Section: Experimental Techniquementioning

confidence: 99%

Nernst effect in Tl-Ba-Ca-Cu-O superconducting films due to infrared laser heating

Lengfellner

Schnellbögl²,

Betz

et al. 1990

Int J Infrared Milli Waves

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A Nernst effect has been observed in a high temperature superconductor for the first time. Irradiating superconducting T1-Ba-Ca-Cu-O thin films by short pulses of a TEA-COs laser, a photovoltaic signal is detected perpendicular to a magnetic field applied parallel to the film surface. The signal is attributed to magnetic flux line depinning and flux line transport driven by the laser induced temperature gradient. The results are described by thermal flux line activation leading to a calcuiated distribution of pinning energies from 100 K to 4000 K.

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“…Because of their high T c (~ 125 K) and high J c , they are readily amenable to operation at liquid nitrogen temperature (~ 77 K). Uptil now, various methods for the preparation of HTSC thin films such as electron beam evaporation (Ramesh et al 1990;Ginley et al 1998a,b;Sugise et al 1998), sputtering (Lengfellner et al 1989;Lin and Wu 1989;Subramanyam et al 1990;Saito et al 1991;Ichikawa et al 1998;Zhou et al 1998), laser ablation (Betz et al 1989;Johs et al 1989), thermal flash evaporation (Barboux et al 1988;Ece and Vook 1989;Verma et al 1989), chemical spray pyrolysis (Kawai et al 1987;Gupta et al 1988;Saxena et al 1988;DeLuca et al 1991;Verma et al 1992) and spin coating (Rice et al 1987) etc have been employed. Out of these techniques, the simple chemical process like spray pyrolysis and spin coating are economically viable.…”

Section: Introductionmentioning

confidence: 99%

Effect of annealing temperature on the structural-microstructural and electrical characteristics of thallium bearing HTSC films prepared by chemical spray pyrolysis technique

2005

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In order to get good quality reproducible films of Tl : HTSC system, we have studied the different annealing conditions to finally achieve the optimized annealing condition. In the present investigation, Tl-Ca-Ba-Cu-O superconducting films have been prepared on YSZ (100) and MgO (100) single crystal substrates via precursor route followed by thallination. The post deposition heat treatments of the precursor films were carried out for various annealing temperatures (870°C, 890°C) and durations (1 and 2 min). The optimized thallination procedure occurred at 870°C for 2 min into good quality films with T c (R = 0) ~ 103 K for YSZ and T c (R = 0) ~ 98 K for MgO substrates, respectively. Further we have correlated the structural/microstructural characteristics of the films.

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Preparation of Tl-Ba-Ca-Cu-O thin films by diffusion of Tl into laser evaporated Ba2Ca2Cu3Ox films

Cited by 12 publications

References 7 publications

Superconducting Tl Ca Ba Cu O thin films prepared by diffusion of Tl into an excimer laser ablated Ca 2 Ba 2 Cu 3 O x film

Superconducting Tl Ca Ba Cu O thin films prepared by diffusion of Tl into an excimer laser ablated Ca 2 Ba 2 Cu 3 O x film

Nernst effect in Tl-Ba-Ca-Cu-O superconducting films due to infrared laser heating

Effect of annealing temperature on the structural-microstructural and electrical characteristics of thallium bearing HTSC films prepared by chemical spray pyrolysis technique

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