Local characterization of HTS thin films by laser scanning microscopy

Korolev, K.A.; Shadrin, P.M.; Preston, John S.; Hughes, Robert A.; Nam, J.; Павловский, В.

doi:10.1016/s0921-4534(00)00976-x

Cited by 5 publications

(5 citation statements)

References 8 publications

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“…In low-temperature laser scanning microscopy, thermoelectric or bolometric voltages induced in the samples by irradiation with a scanned laser beam are utilized to image the transport properties of the grain boundaries, with submicrometer resolution at best (Divin et al, 1991;Shadrin et al, 1998Shadrin et al, , 1999Korolev et al, 2000).…”

Section: Viid)mentioning

confidence: 99%

Grain boundaries in high-Tcsuperconductors

2002

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Since the first days of high-T c superconductivity, the materials science and the physics of grain boundaries in superconducting compounds have developed into fascinating fields of research. Unique electronic properties, different from those of the grain boundaries in conventional metallic superconductors, have made grain boundaries formed by high-T c cuprates important tools for basic science. They are moreover a key issue for electronic and large-scale applications of high-T c superconductivity. The aim of this review is to give a summary of this broad and dynamic field. Starting with an introduction to grain boundaries and a discussion of the techniques established to prepare them individually and in a well-defined manner, the authors present their structure and transport properties. These provide the basis for a survey of the theoretical models developed to describe grain-boundary behavior. Following these discussions, the enormous impact of grain boundaries on fundamental studies is reviewed, as well as high-power and electronic device applications. CONTENTS I. Introduction 485 II. Introduction to Grain Boundaries 486 III. Preparation of Single Grain Boundaries 488 A. Bicrystalline junctions 489 B. Biepitaxial junctions 489 C. Step-edge junctions 491 IV. Structural Properties 491 V. Transport Properties of Grain Boundaries 496 A. Current-voltage characteristics 496 B. Critical current density 498 1. Dependence on grain-boundary angle 498 2. Temperature dependence of the critical currents 502 3. Magnetic-field dependence of the critical currents 502 C. Current-phase relation 504 D. Normal-state resistivity 504 E. The I c R n product 505 F. Grain-boundary capacitance 506 G. Microwave properties 507 H. Grain-boundary noise 507 I. Self-generated magnetic flux 509 J. Penetration of magnetic flux into grain boundaries 510 VI. Effects of Doping 510 VII. Grain-Boundary Mechanisms 511 A. Mechanisms based on structural properties 511 B. Mechanisms based on deviations from ideal stoichiometry 512 C. Order-parameter symmetry-based mechanisms 514 D. Interface charging and band bending 515 E. Mechanisms based on direct suppression of the pairing mechanism 516 VIII. Control of Grain Boundaries with Electric Fields or Quasiparticle Injection 517 A. Applied electric fields 517 B. Quasiparticle injection 518 IX. Irradiation of Grain Boundaries 518 A. Irradiation with electrons 518 B. Irradiation with light 518 C. Irradiation with ions 519 X. Bulk Applications 519 A. Powder-in-tube method 520 B. Coated conductors 520 XI. Applications of Grain Boundaries in Thin Films 522 A. SQUIDs 522 B. Radiation detectors and spectrometers 524 C. Three-terminal devices 525 D. Superconducting logic circuits 526 E. Research devices 526 XII. Summary and Outlook 528 Acknowledgments 529 References 529

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Section: Viid)mentioning

confidence: 99%

Grain boundaries in high-Tcsuperconductors

2002

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“…By scanning the beam it becomes possible to determine the sample's local electrical characteristics. The technique is well suited for determining the electrical homogeneity of a superconducting thin film [3], [4], [9]- [11].…”

Section: Laser Scanning Microscopymentioning

confidence: 99%

“…This reduces the overall current carrying capacity of the film. The image obtained by rastering the beam can be used to determine the homogeneity of local current carrying capacity of the film [3], [4]. The second mode allows for a thermoelectric measurement that is carried out on an unbiased bridge.…”

Section: Laser Scanning Microscopymentioning

confidence: 99%

“…A thermoelectric voltage is obtained by inducing a temperature gradient in the film using the focused laser beam. Any electrical defects, such as a grain or a bi-crystal junction will produce a response with odd-symmetry [3], [4], [10], [11] meaning that the voltage obtained on one side of the boundary will be equal in magnitude, but opposite in sign to the one obtained on the other side of the boundary. This mode, therefore, provides a method to identify the location of defect boundaries.…”

Section: Laser Scanning Microscopymentioning

confidence: 99%

“…Boundaries inside a grain were the least resistive, followed by boundaries between grains with the same microtwin orientation. The most resistive boundaries were those between grains with a perpendicular microtwin orientation [3], [4]. The extent of the microtwinning in thin films has made it difficult to study the transport properties of individual twin boundaries as the length scales involved are inaccessible to the LSM technique.…”

Section: Introductionmentioning

confidence: 99%

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Laser Scanning Microscopy Studies on Detwinned<tex>$rm YBa_2rm Cu_3rm O_7-delta$</tex>Thin Films

Nam

Hughes

Dąbkowski

et al. 2005

IEEE Trans. Appl. Supercond.

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YBa 2 Cu 3 O 7 thin films are heavily microtwinned due to the crystal's orthorhombic unit cell and the confining effects of underlying substrate. Single crystal YBCO can be detwinned by thermally annealing the sample while applying uniaxial pressure. A similar technique has been devised to detwin a portion of a YBCO thin film. Through the use of photolithographic techniques, a suspended YBCO microbridge structure is fabricated, but with both ends of the bridge anchored to the substrate. During a subsequent anneal, the ends of the bridge induce a uniaxial stress along its length that arises from the lattice misfit and the thermal expansion coefficient mismatch between YBCO and the underlying materials. Without the confining effects of the substrate the suspended material can either detwin or twin on a macro length scale; the extent of which is largely determined by the substrate material. The ability to produce superconducting YBCO bridges that range from heavily microtwinned, to macrotwinned, to nearly detwinned provides an ideal experimental system. To study these phenomena, an optical and laser scanning microscopy set-up was employed. The images obtained provide insight into the role that twins play in determining the transport properties of superconducting YBCO thin films.

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Detwinning YBa2Cu3O7−δ thin films

Nam

Hughes

Dąbkowski

et al. 2003

Applied Physics Letters

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Single crystals of YBa2Cu3O7-δ (YBCO) have been detwinned under the simultaneous application of heat and uniaxial stress. This approach, however, has proved futile in thin films as they become heavily twinned due to strain from the underlying substrate as well as the orthorhombic unit cell. This lack of control over twinning has made it difficult to determine the role that twins play in determining the transport properties of films. Here, we present a technique for detwinning YBCO thin films. The detwinning in YBCO thin film is achieved by suspending a portion of the YBCO film above the underlying substrate. The suspended material is no longer influenced by the confining effects of the substrate and this allows it to detwin under the application of a uniaxial stress brought about by an anneal. With this technique, we are able to produce high-quality detwinned regions that will help aid the understanding of transport mechanisms in YBCO.

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Local characterization of HTS thin films by laser scanning microscopy

Cited by 5 publications

References 8 publications

Grain boundaries in high-Tcsuperconductors

Grain boundaries in high-Tcsuperconductors

Laser Scanning Microscopy Studies on Detwinned<tex>$rm YBa_2rm Cu_3rm O_7-delta$</tex>Thin Films

Detwinning YBa2Cu3O7−δ thin films

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Local characterization of HTS thin films by laser scanning microscopy

Cited by 5 publications

References 8 publications

Grain boundaries in high-Tcsuperconductors

Grain boundaries in high-Tcsuperconductors

Laser Scanning Microscopy Studies on Detwinned&lt;tex&gt;$rm YBa_2rm Cu_3rm O_7-delta$&lt;/tex&gt;Thin Films

Detwinning YBa2Cu3O7−δ thin films

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Laser Scanning Microscopy Studies on Detwinned<tex>$rm YBa_2rm Cu_3rm O_7-delta$</tex>Thin Films