Characterisation of the surface morphology and electronic structure of YBa2Cu3O7-x thin films by atomic force and scanning tunneling microscopies

AFM, STM and STS techniques have been used to characterise the surface morphologies and electronic structures of YBCO films. All of the films prepared under optimum laser deposition conditions exhibited dominant spiral growth features. Besides, layer growth cakelike shaped crystal grains were also frequently observed. The (I-V) curve analysis indicated that the spiral or layer-by-layer growth grains exhibited a metallic tunneling behaviour, while the particulates on the films showed typical semiconductor tunneling behaviour. In addition, some tiny insulator inclusions have also been revealed by CITS analysis.