Surface degradation of YBa2Cu3O7−δ observed by means of contact resistance measurement

Grajcar, M.; Plecenı́k, A.; Darula, M.; Beňačka, Š.

doi:10.1016/0038-1098(92)90387-o

Cited by 18 publications

(13 citation statements)

References 14 publications

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“…The observed decrease of the surface conductivity over time is in agreement also with works done on YBCO/metal contacts [5]. Effects shown in Fig.…”

Section: Resultssupporting

confidence: 91%

“…Relatively low activation energy for the oxygen diffusion in the YBCO, which has been shown by various experiments to be in range from ~0.5 to ~1.3 eV within the material and about ~1.7 eV for out-diffusion from the surface [2][3][4][5], leads to leakage of the oxygen out of the YBCO surface and spontaneous creation of a degraded insulating near-surface layer with decreased amount of oxygen content [5][6][7]. This is a big challenge in many applications where well defined and sharp interfaces between HTS and electrodes are required.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

Truchlý

Pleceník

Krško

et al. 2012

Physica C: Superconductivity

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Local surface conductivity properties and surface degradation of c-axis oriented YBa 2 Cu 3 O 6+x (YBCO) thin films were studied by Scanning Spreading Resistance Microscopy (SSRM). For the surface degradation studies, the YBCO surface was cleaned by ion beam etching and the SSRM surface conductivity map has been subsequently repeatedly measured over several hours in air and pure nitrogen. Average surface conductivity of the scanned area was gradually decreasing over time in both cases, faster in air. This was explained by oxygen out-diffusion in both cases and chemical reactions with water vapor in air. The obtained surface conductivity images also revealed its high inhomogenity on micrometer and nanometer scale with numerous regions of highly enhanced conductivity compared to the surroundings. Furthermore, it has been shown that the size of these conductive regions considerably depends on the applied voltage. We propose that such inhomogeneous surface conductivity is most likely caused by varying thickness of degraded YBCO surface layer as well as varying oxygen concentration (x parameter) within this layer, what was confirmed by scanning Auger electron microscopy (SAM). In our opinion the presented findings might be important for analysis of current-voltage and differential characteristics measured on classical planar junctions on YBCO as well as other perovskites.

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“…The observed decrease of the surface conductivity over time is in agreement also with works done on YBCO/metal contacts [5]. Effects shown in Fig.…”

Section: Resultssupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

Truchlý

Pleceník

Krško

et al. 2012

Physica C: Superconductivity

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“…As was shown in Ref. 18, the degradation processes near the HTS interface are diffusion-like and the oxygen concentration gradually decreases from the bulk to the HTS surface where a depleted layer is formed. It is in the disordered state because of the disordered oxygen vacancies and will be modeled further as a nonsuperconducting N' layer with variing width 1 along the contact (see the right part of Fig.…”

Section: Zero Bias Anomaliessupporting

confidence: 57%

Influence of degraded surface layer of HTS on differential conductance of HTS/metal junctions

Seidel

Grajcar

Plecenı́k³

et al. 1998

SPIE Proceedings

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We have performed a detailed study of the effect of the HTS degraded surface layer on conductance spectra of HTS/metal junctions. It has been found that the corresponding resistance changes by applying an external bias voltage can be explained as an alteration of the oxygen content near the interface. To take into account the spatially inhomogeneous nature of a few top HTS unit cells, we have examined theoretically the influence of a nonuniform normal covering on the subgap tunneling characteristics of a superconductor. A simple approach to coherent charge transport through a planar double-barrier structure has been generalized to the case of an anisotropic order parameter, non-uniformity of the middle nonsuperconducting layer, and magnetic field effect. In particular, we show that, under suitable circumstances, the conductance peak at zero bias voltage and its splitting at low temperatures often observed for HTS/metal junctions can be interpreted within the s-wave scenario, too, if above mentioned inhomogeneity is considered.

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“…1 an increase in point contact resistance immediately after preparation is shown. This change was explained in the term of out-diffusion of oxygen from surface layer of HTS near HTS/metal interface caused by lower activation energy of oxygen on the surface [15]. On the base of our results we assume the lowering of the surface barrier for out-diffusion of oxygen from HTS due to Schottky effect.…”

Section: Degradation Processes In the Surface Layermentioning

confidence: 50%

“…±0.5 V -±2 V. This effect we explained by rapid changes of oxygen concentration in HTS near HTS/metal interface caused by the electric field or/and electromigration. The changes of oxygen content directly yield a change of resistivity in HTS near the interface [15,17,18].…”

Section: Degradation Processes In the Surface Layermentioning

confidence: 99%

Tunneling and Point Contact Spectroscopy of High-T_cSuperconducting Thin Films

1998

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Tunneling and point contact junctions between a normal metal and thin high temperature superconducting film were studied to obtain information on snrface properties. Surface degradation and time development of contact resistance are investigated as well as peculiarities of the conductance-voltage characteristics. The quasi-linear background is related to carrier transport through degraded surface layer described by a model of inelastic scattering from a broad flat continuum of states inside the potential barrier. An asymmetry of the characteristics appears as the result of low Fermi energy values in the high temperature superconductors in comparison to common metals. An extrinsic nature of these peculiarities is supported by effects of barrier formation by applied voltages in the 1 volt range. As an often observed anomaly a conductance peak at zero bias is observed which can be related to different mechanisms. In the case of high temperature superconductors this zero bias anomaly is related to the d-wave pairing symmetry of the pair potential. Experimental results on YBCO and BSCCO films are compared to calculations taking into account the Andreev reflections for a junction between a normal metal and a d-wave superconductor.

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Surface degradation of YBa2Cu3O7−δ observed by means of contact resistance measurement

Cited by 18 publications

References 14 publications

Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

Influence of degraded surface layer of HTS on differential conductance of HTS/metal junctions

Tunneling and Point Contact Spectroscopy of High-T_cSuperconducting Thin Films

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Surface degradation of YBa2Cu3O7−δ observed by means of contact resistance measurement

Cited by 18 publications

References 14 publications

Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

Influence of degraded surface layer of HTS on differential conductance of HTS/metal junctions

Tunneling and Point Contact Spectroscopy of High-TcSuperconducting Thin Films

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Tunneling and Point Contact Spectroscopy of High-T_cSuperconducting Thin Films