Comparisons of high temperature superconductor thin films on various substrates for microwave applications

Young, K. H.; Negrete, G. V.; Eddy, M. M.; Sun, Jian; James, T. W.; Robinson, McD.; Smith, E. J.

doi:10.1016/0040-6090(91)90403-k

Cited by 22 publications

(4 citation statements)

References 14 publications

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“…The criteria governing the choice of substrate are dictated by the requirements of both the intended application and the desire to induce epitaxial film growth. Substrate selection for HTS thin-film growth is covered in depth in a number of review articles [102][103][104], but these generally concentrate on the growth of YBCO films on the available substrate materials. The choice of substrate for the deposition of Tl-based HTS phases, particularly by ex situ deposition methods, is further constrained by the need to avoid film-substrate reactions during the high-temperature thalliation anneal.…”

Section: Substrate Selectionmentioning

confidence: 99%

Thallium-based HTS thin films, processing, properties and applications

Bramley¹,

O'connor²,

Grovenor³

1999

Supercond. Sci. Technol.

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Thin films of the Tl-based high-temperature superconducting (HTS) phases are beginning to find application in a number of practical devices, especially in the field of microwave communication systems. This review describes the issues surrounding the fabrication of thin films of the thallium-based HTS materials. The influence of thermodynamics and kinetics, the various potential thalliation techniques and the selection of an appropriate substrate material are all important considerations when designing a process for the fabrication of thin films of these highly reactive materials. The properties of the resulting films are critically dependent on the microstructures developed during thalliation. Microstructural evolution during thalliation, the effect of structural defects on the properties of such films and the importance of achieving biaxial grain alignment in optimizing the properties of the films are all discussed.

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Section: Substrate Selectionmentioning

confidence: 99%

Thallium-based HTS thin films, processing, properties and applications

Bramley¹,

O'connor²,

Grovenor³

1999

Supercond. Sci. Technol.

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“…5 For these devices, substrate selection is critical, and single-crystal substrates with a relatively low dielectric constant are needed for optimal performance. LaAlO 3 ͑LAO͒ is particularly interesting since it exhibits a low loss, a relatively low dielectric constant (⑀ r ϭ24, at 77 K and 2 GHz͒, 6 a good lattice match to STO ͑ϳ3%͒, and a high chemical stability at typical STO growth conditions. Different deposition methods have been used to synthesize STO films, such as, laser ablation, 7 radio frequency ͑rf͒ sputtering, 8 metalorganic chemical vapor deposition, 9 ozone assisted molecular beam epitaxy, 10 and sol-gel techniques.…”

Section: Introductionmentioning

confidence: 99%

Composition, structure, and dielectric tunability of epitaxial SrTiO3 thin films grown by radio frequency magnetron sputtering

Wang¹,

Helmersson²,

Madsen³

et al. 1999

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Epitaxial (001) oriented SrTiO3 films have been deposited on LaAlO3(001) substrates by off-axis radio frequency magnetron sputtering in Ar:O2 gas mixtures at substrate temperatures ranging from 650 to 850 °C. For the deposition conditions used, stoichiometric targets yielded 20% Sr-deficient films, whereas Sr-enriched targets (Sr1.1Ti0.9O3.0) resulted in stoichiometric films. The Sr-deficient films had a mosaic structure and a larger lattice parameter in comparison to bulk SrTiO3. The stoichiometric films on the other hand had a much higher crystalline quality in the as-deposited condition. The mosaicity of the latter films was primarily limited by the crystalline quality of the LaAlO3 substrates. The lattice parameters of the stoichiometric films were also smaller than the Sr-deficient ones and closer to the bulk value. The dielectric properties of the stoichiometric films were superior to the Sr-deficient films. For films with a thickness of ∼300 nm, the typical dielectric constants as measured at ∼77 K and 1 MHz were determined to be 820 and 500, for the stoichiometric and Sr-deficient films, respectively. Also the capacitance change, as a direct current bias voltage was applied to an interdigital capacitor, was higher for the stoichiometric film, 27.3% as compared to 8.6% when applying a bias of 300 V at 77 K. We also demonstrate the effectiveness of thermal annealing in improving both crystalline quality and dielectric properties, especially for the Sr-deficient films.

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“…The linear thermal expansion coefficients of the LCMO and LAO compounds are close in magnitude [11,12].…”

Section: Resultsmentioning

confidence: 88%

10.1007/s11451-008-3009-5

2010

CrossRef Listing of Deleted DOIs

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The structure and electrical resistance of La 0.67 Ca 0.33 MnO 3 (40 nm) epitaxial films grown quasicoherently on the surface of LaAlO 3 (001) substrates are investigated. Compressive mechanical stresses that are active in the substrate plane during nucleation and growth encourage a decrease in the effective unit cell volume and an increase in the relative concentration of tetravalent manganese ions in the manganite layers. This leads to a decrease in the temperature of the maximum in the temperature dependence of the electrical resistivity of the films by approximately 90 K compared to the Curie temperature for the corresponding stoichiometric bulk crystals. It is found that, at T < 120 K and µ 0 H = 0 (where H is the magnetic field strength), the measuring current depends nonlinearly on the voltage V b applied to the contacts. An increase in the applied voltage V b and in the magnetic field strength H favors linearization of the current-voltage characteristics of the films.

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Comparisons of high temperature superconductor thin films on various substrates for microwave applications

Cited by 22 publications

References 14 publications

Thallium-based HTS thin films, processing, properties and applications

Thallium-based HTS thin films, processing, properties and applications

Composition, structure, and dielectric tunability of epitaxial SrTiO3 thin films grown by radio frequency magnetron sputtering

10.1007/s11451-008-3009-5

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