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The effect of sputter deposition conditions on the growth mechanism of YBa2Cu3O7-delta thin films studied by scanning tunnelling microscopy
G.S. Shekhawat, R.P. Gupta, , K.B. Garg, P.D. Vyas
Published in
Volume: 8
Issue: 5
Pages: 291 - 295
Surface topography of as-grown films of YBa2Cu3O 7-delta (YBCO) deposited by off-axis RF magnetron sputtering on MgO and SrTiO3 single-crystal (100) substrates, has been investigated by scanning tunnelling microscopy (STM)/scanning tunnelling spectroscopy (STS) operated in air at ambient temperature. Both c-axis- and a-axis-oriented YBCO films have been investigated. In the case of c axis thin films, we have directly observed spiral-shaped growth terraces, which emanate from screw dislocations of this layered superconducting oxide. The growth steps are generally seen to possess a step height close to or multiples of the unit cell height of the YBCO crystalline structure. In the case of a axis growth, the substrate as well as the deposition temperature determines the grain orientation. Furthermore, our STS data revealed that the surface layer of the film is semiconducting and the tunnelling spectrum varies its shape depending on the tip-to-sample distance. A superconducting gap appears clearly in the spectra when the STM tip is placed closer to the surface than the normal position of the scanning mode. This suggests that the semiconducting layer is confined in the topmost surface region of the as-prepared film, while the layer beneath it is superconducting in character.
About the journal
JournalSuperconductor Science and Technology