Characterization of defect modes in YBa2CU3O7-δ thin films probed by Raman scattering

초록

A Raman analysis is performed on a series of fully oxygenated YBa2Cu3O7-delta thin films, on MgO(100) substrates, deposited by the pulsed laser technique at temperatures between 680degreesC and 820degreesC. theta-2theta scans of the films by the Xray diffraction show that the YBCO films are oriented in the c-axis. There are no extra peaks appearing in the X-ray diffraction data. Besides the well-known active modes, however, Raman spectra reveal a number of defect modes. The defect mode at 594 cm(-1) redshifts and merges toward the O(4)-A(g) mode at 502 cm(-1) with decreasing deposition temperatures. This mode is significantly asymmetrical and broad, whereas the mode at 243 cm(-1) is symmetrical, with a small full width at half maximum remaining unchanged at a value around its own frequency. The intensity of the mode at 243 cm(-1) seems to depend on the intensity of the mode at 594 cm(-1). Quantitative calculations concerning the relative intensities show that the two modes are related to each other. (C) 2004 Elsevier B.V. All rights reserved.

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