Electron and scanning probe microscopies in the study of YBa2Cu3O7 thin-film growth

Abstract

Electron and scanning probe microscopies are used to examine the microstructure and surface topography of YBa2Cu3O7 (YBCO) thin films formed by pulsed-laser deposition (PLD). A major emphasis of this work has been the correlation of the observed microstructural features and the deposition parameters.The formation of microscopic features on the surface of thin films deposited by PLD seems to be an undesirable and almost unavoidable feature of this process. One such feature is often associated with microstructural changes produced in the target during laser irradiation. These are apparently spherical particles with diameters ranging from 0.1 to 10μm. These particles are produced by melting of the target and the subsequent solidification of the molten ejecta. Particles may also be produced as a result of changes in the surface morphology of the target during laser irradiation. However, notall surface features observed on the films deposited by PLD are due to ejecta from the target. Figure 1 shows an atomic force microscope (AFM) image of a YBCO film grown on a (100)-oriented LaAlO3 substrate. Usually films grown with our typical deposition conditions on (100)-oriented LaAlO3 substrates arepredominantly c-axis oriented. The film is approximately 150 nm thick. Different types of outgrowth are visible on the film surface.