Quantitative image analysis of superconductor thin film microstructure: The use of conditional, multiparametric, shape-a
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Mark Lelental Ceramics Science Laboratory-Corporate Research Laboratory, Eastman Kodak Company, Rochester, New York 14650
Ray C. Bowen Analytical Technology Division, Eastman Kodak Company, Rochester, New York 14650 (Received 6 January 1993; accepted 20 July 1993)
We have developed a novel approach for quantifying the microstructure of granular thin films using digital image processing and analysis. In the past, conventional scanning electron microscopy of thin films has generated qualitative information on the surface topography and film microstructure. However, when coupled to digital image analysis, the amount or degree of surface contours (i.e., granularity) in SEM micrographs can be quantified in a rapid and reproducible manner. Briefly, SEM micrographs are digitized and the edge boundaries on the film surface are enhanced by a gradient filter; granularity is then quantified by calculating the %AREA covered by the edges with respect to the entire field. Objects of a particular shape, such as phase impurity particles, can be selectively deleted from the image using a specific sequence of shape analysis algorithms and parameter values. In this manner, the contributions of edges from the phase impurity particles is minimized in the final measurement of real surface contours. Statistical analysis of the data yields quantitative information concerning variations in microdomains within single thin films and can detect statistically significant differences among samples. This method is being used in the characterization of the microstructure of superconducting thin films for optimization of their electrical and magnetic properties.
I. INTRODUCTION Large-scale practical application of high-temperature ceramic superconductor tapes awaits the development of thin or thick films capable of carrying current in excess of 105 A/cm 2 . Attempts to produce such films have so far met with considerable difficulty. It is generally accepted that highly textured films are required for the efficient transport of intergranular currents. This requirement is associated with the anisotropic nature of superconducting properties of copper oxide based ceramics. Therefore, the characterization of the microstructure of films of superconducting cuprates is of great importance for optimization of their electrical and magnetic properties.1 Characterization of thin films by direct (scanning electron microscopy, transmission electron microscopy, field ion, and optical microscopy) and indirect (spectroscopic ellipsometry, image enhancement and analysis of morphology photographs, small angle x-ray and electron scattering, and computer simulations of film growth) methods has been reviewed by Messier.2 The application of digital image processing and analysis to J. Mater. Res., Vol. 8, No. 11, Nov 1993 http://journals.cambridge.org
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microscopy images is growing rapidly,3 7 especially for materials.8"10 The objective of this work was to design and implement an analytical method that will quantify the amount of surface micros
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