Quantitative structure analyses ofYBa2Cu3

Jinhua Ye

¹

,

Keikichi Nakamura

²

Abstract

Quantitative structure analyses of YBa2cu, O, s thin films, prepared by radio-frequency sputtering and molecular-beam-epitaxy methods, have been carried out with the x-ray-diffraction method. The expansion in c-lattice parameters of the as-grown thin films were found to be caused by one of the following factors or a combination of them: lattice defects introduced during deposition, deficiency of oxygen, and the disordering of Y and Ba atoms. To study phenomena concerning the deficiency of oxygen, further investigations were carried out with the use of experimentally controlled oxygen-deficient thin films with 6 values ranging from 0.07 to close to 1.0. Systematic changes in the c-lattice parameters and diffraction intensities with increasing 5 were observed; also, a very convenient method for the quantitative determination of oxygen content in the thin films determined from the ratio of the integrated intensity of 005 to 006 reAections has been established. Structure analyses of the oxygen-deficient thin films revealed that the oxygen dependence of the structural parameters in the thin films are similar to that reported for bulk samples. Electrical-resistivity measurements showed that the thin films exhibit clearly a "two-plateau" T, versus 6 behavior.

Study of in-plane electrical transport anisotropy of a -axis oriented YBa2Cu3O7−δ nanodevices

“…In the normal state, a strong anisotropy is present: the resistance in the c-axis direction is ≈100 times larger than in the the b-axis direction just above the superconducting transition, in agreement with earlier reports on untwinned YBCO single crystals [29,30]. The behavior of the resistance with the temperature is also anisotropic: along the b axis, the resistance shows a linear temperature dependence from 300 K down to the superconducting transition, which is typical of optimally doped films [31]; along the c axis, the range of linearity decreases, and a downward bending of the resistance with the temperature, resembling that of an underdoped YBCO c-axis film, develops at low temperatures. Finally, we have recorded a critical temperature T C ≈ 88 K along both the YBCO in-plane directions, calculated as the temperature where the derivative dR/dT is maximum, and a transition broadening T C ≈ 3 K.…”

The superconducting transition width and illumination wavelength dependence of the response of MgO substrate YBCO transition edge bolometers

“…The dependence of the transition width on oxygen content has been studied by some groups. For example, Ye and Nakamura [24] and Cogollo et al [25] ascribe the broad resistive transitions of the YBCO bolometers to the amount of oxygen deficiency and Uchiyama et al attribute it to nonuniformity of the oxygen content (7 À d) in the YBCO thin film [26]. We investigated the effect of precipitates on the superconducting transition width.…”

Evaluation ofCuO2plane hole doping inYBa2Cu3O6+xLiang1, Bonn2, Hardy3 2006Phys. Rev. B374443801View full textAdd to dashboardCite

“…The change in c is mainly caused by the change in d Cu(2)-O(4) because it is much more sensitive to change in the oxygen content than other bond lengths. The lattice parameter c can be easily measured to high precision by diffraction techniques and there has been considerable work [7][8][9][10][11][12] on the relationship between c and the oxygen content of YBCO. However, by examining the data for our single crystals we have found that the dependences of p and c on the oxygen content are not unique: both p and c depend not only on the oxygen content but also on the degree of oxygen ordering in the Cu(1)-O chains.…”