Three-dimensional observation of microstructures in Y123 films fabricated by TFA-MOD method

We were successful for three-dimensional imaging of microstructures in YBa₂Cu₃O_7-y (Y123) films fabricated by metal organic deposition using trifluoroacetates (TFA-MOD) method. We have reported previously, that a transmission electron microscopy (TEM) analysis clarified microstructures such as Y123 crystal grains and pores in the Y123 films. In order to derive important parameters for enhancement of superconducting properties of the Y123 films, quantitative analyses of those microstructures are required. Then, control of both pores and a-axis oriented grains distribution in the Y123 films are important. However, general TEM images provide only a two-dimensional projection of a three-dimensional object. An electron tomography is an effective technique for three-dimensional structure analysis of various materials. Cross-sectional view specimen for the three-dimensional electron tomography was prepared by focused ion-beam milling equipped with micro-sampling system. A scanning transmission electron microscopy - annular dark field technique was used for the present three-dimensional electron tomography. For the cross-sectional specimen of fired Y123 films, three-dimensional shapes and distributions of both pores and unreacted phases were observed in reconstructed images. Also, morphologies of the Y123 film surface were clearly seen.