High critical current density ultrathin YBa2Cu3O<i>x</i> films made by a modified rf-magnetron sputtering technique

Gao, J.; Häuser, B.; Rogalla, Horst

doi:10.1063/1.345503

Cited by 73 publications

(18 citation statements)

References 4 publications

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“…An exception occurs if the field is confined to one side of the film ( H I or H2 = 0), meaning that the film represents a real wall. Then the surface impedance reads as: (26) which is in agreement with the usual expression for this case [121. The general pattern of Z, 1 and Z,Z is shown in Fig. 1 at a frequency f = 10 GHz, with a penetration depth X = 100 nm and skin depth 6 = 1OOX.…”

Section: A Surface Impedance Of a Film Of Arbitrary Thicknesssupporting

confidence: 73%

“…The measurements are performed in the temperature range of 4.2 to 80 K at excitation levels for which the data are independent of incident microwave power (-30 dBm). The thin films are deposited on sapphire substrates by off-axis rf magnetron sputtering [26]. A c-axis oriented YBazCu307-, layer is separated from the substrate by a PrBapCu307-, buffer layer, both layers having a thickness of 50 nm.…”

Section: Resultsmentioning

confidence: 99%

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The propagation characteristics of wave-guiding structures with very thin superconductors; application to coplanar waveguide YBa/sub 2/Cu/sub 3/O/sub 7-x/ resonators

Klopman

Gerritsma

Rogalla

1993

IEEE Trans. Microwave Theory Techn.

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Abstrucf-We have analyzed the propagation characteristics of wave-guiding structures with superconductors which are thin compared to the magnetic penetration depth. The complex propagation constant is evaluated within the framework of the modified spectral domain method without the need for numerical calculations in the complex plane. Good agreement is found with the results of other methods. The numerical analysis is instrumental in deducing results for the penetration depth and the surface resistance of Y B a 2 C~3 0 7~~ thin films on sapphire with a PrBa2Cu307--s buffer layer. We confirm recent observations of a non-single-gap BCS temperature dependence.

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Section: A Surface Impedance Of a Film Of Arbitrary Thicknesssupporting

confidence: 73%

Section: Resultsmentioning

confidence: 99%

The propagation characteristics of wave-guiding structures with very thin superconductors; application to coplanar waveguide YBa/sub 2/Cu/sub 3/O/sub 7-x/ resonators

Klopman

Gerritsma

Rogalla

1993

IEEE Trans. Microwave Theory Techn.

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“…Experimental details can be found elsewhere [16,17]. As substrates yttria-stabilized ZrO 2 (YSZ) (10t3) single crystals were used.…”

Section: Methodsmentioning

confidence: 99%

“…The basis for high-T~ superconducting devices will be formed by high-7~, supercnnducting multilayer structures [16][17][18][19][20]. The composition of interfaces in these structures plays a very important role and it strongly affects the performance of high-T, superconducting devices.…”

Section: Introductionmentioning

confidence: 99%

Quantitative analysis of X-ray photoemission spectra, acquired on c-axis oriented high-Tc superconducting YBa2Cu3O7−δ thin films

Aarnink

Gao

Rogalla

et al. 1992

Applied Surface Science

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Angle-resolved X-ray photoemission spectroscopy (ARXPS) was performed on c-axis oriented high-T~ superconducting YBa,Cu30 , ~ thin films. The layered structure of the YBa2Cu30 7 ~ films was used to develop a model for the quantitative analysis of the ARXPS experiments. Our XPS results may be compared to spectra taken on YBazCu30 7_~ single-crystal surfaces. On the spectra features are superposed that are assigned to a thin non-superconducting surface layer. For the first time. relative ARXPS measurements show that the interface between the superconducting YBa,Cu3OT_,~ film and the surface layer is formed by the atomic Y layer. The surface layer consists mainly of BaCO~ and C. A small volume fraction ( ~ 20%) contains Ba-and Cu-oxides. probably in the form of BaCuO 2. From absolute ARXPS measurements, the thickness of the surface layer was calculated to be 11.93 + 11.06 nm. It is shown that the surface roughness of our films is on the order of 0.6 rim. A good agreement between theory and experiment has been found in this report.

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“…6. The deposition of the CeO 2 was done by pulsed laser ablation, using an eximer laser ͑XeCl mode; ϭ308 nm͒, 75 mJ pulse, pulse rate 1 Hz, spot size 6.4 mm 2 , from a 99.9% pure CeO 2 target.…”

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CeO2 as insulation layer in high T c superconducting multilayer and crossover structures

Wijck

Verhoeven

Reuvekamp

et al. 1996

Applied Physics Letters

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We present a study of the electrical properties of insulating CeO 2 layers in combination with superconducting ͑Y/Dy͒ Ba 2 Cu 3 O 7Ϫ␦ ͑RBCO͒ films over ramps and in crossover structures. CeO 2 is frequently used as a buffer layer, or template layer for biepitaxial grain boundary junctions, but can also be used as an insulating layer in ramp-type junctions and other multilayer structures. Epitaxial thin films of CeO 2 were deposited by pulsed laser ablation using SrTiO 3 substrates. We characterized the insulating performance of CeO 2 thin films in terms of breakdown field E bd and the relative dielectric constant ⑀ r . For 80 nm thick CeO 2 at 77 K we found E bd ϭ1ϫ10 6 V/cm, using a 1 nA/100 m 2 breakdown criterion, which gives us a specific resistivity of у10 9 ⍀ cm up to breakdown. From capacitance measurements on planar RBCO/CeO 2 /RBCO structures we obtained for the dielectric constant: ⑀ r Ϸ15. The texture of CeO 2 in combination with RBCO on ramped surfaces, simulated by SrTiO 3 ͑STO͒ ͑103͒ substrates having their normal tilted by 18°away from the STO͓001͔ direction, has been studied by x-ray diffraction. © 1996 American Institute of Physics. ͓S0003-6951͑96͒02604-6͔High-quality heteroepitaxial multilayers of superconductors and insulators are required for high T c superconducting electronic devices, like ramp-type junctions and crossover structures in multiturn coils. For the use in highfrequency applications, an insulator having a low dielectric constant is preferred to reduce capacitive shunting. Materials often used as insulators in high T c superconducting devices are PrBa 2 Cu 3 O 7 ͑PBCO͒ 1 and SrTiO 3 ͑STO͒. 2 The use of PBCO has some disadvantages for its relatively low resistivity at 77 K and the anisotropic growth. The last property enhances the formation of granular films, and leaks are likely to occur at boundaries between a-and c-axis oriented grains. The main drawback of STO is its large dielectric constant ͓⑀ r Ϸ300 for thin films ͑Ref. 2͔͒, which severely limits its applicability in high-frequency devices. CeO 2 has been shown to be useful as a planar insulator. 3 It has a cubic crystal structure with lattice constant a 0 ϭ5.411 Å, and CeO 2 ͓100͔ is commensurate with YBCO͓110͔, corresponding to a relative rotation of 45°of the lattices. The very simple crystal structure, containing only one metal ion and oxygen, makes CeO 2 an easy material to grow by pulsed laser deposition, as no problems with the stoichiometry are to be expected. The use of CeO 2 in ramp-type junctions and crossover structures requires a nearly perfect heteroepitaxy with RBCO, both on top of flat surfaces and on artificially created ramped surfaces. The rotation of CeO 2 relative to RBCO, however, might induce grain boundaries or cracks when growing on a ramped surface. Reuvekamp et al. 4 showed that the preferential orientation of RBCO grown on YSZ is with the c-axis perpendicular to the local YSZ substrate surface. The difference in orientation in the upper YBCO layer on the ramp and on flat surfaces then caused cr...

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High critical current density ultrathin YBa2Cu3Ox films made by a modified rf-magnetron sputtering technique

Cited by 73 publications

References 4 publications

The propagation characteristics of wave-guiding structures with very thin superconductors; application to coplanar waveguide YBa/sub 2/Cu/sub 3/O/sub 7-x/ resonators

The propagation characteristics of wave-guiding structures with very thin superconductors; application to coplanar waveguide YBa/sub 2/Cu/sub 3/O/sub 7-x/ resonators

Quantitative analysis of X-ray photoemission spectra, acquired on c-axis oriented high-Tc superconducting YBa2Cu3O7−δ thin films

CeO2 as insulation layer in high T c superconducting multilayer and crossover structures

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