A fuzzy logic approach to HREM image analysis of III-V compounds

Among advanced theories, fuzzy logic (FL) is highly suited for image analysis. It is known that high-resolution electron micrographs (HREM) can provide information on the nature of crystals. For studying interdiffusion phenomena in layered structures of III-V compounds, image variations, described by the term similarity, have to be correlated with the chemical properties of the III-V crystal cells, called composition. Applying difference measures in terms of ''similarity'' for comparing image cells with known equilibrium templates, two data matrices are extracted. To adapt the latter to FL, triangular membership functions are employed. The composition is arrived at by applying the set of fuzzy rules formulated to an oriented mask of two neighboring cells. In order to draw meaningful conclusions, all resulting fuzzy sets are defuzzified by applying the popular ''center of gravity'' method. The fuzzy logic tool designed provides chemical composition maps (3D) and the corresponding concentration profiles of the HREM images of III-V crystals. It is applied to interpret simulated contrast tableaus of GaAs/P (As/P variation) as well as experimental micrographs of MBE-grown Al/GaAs (Al/Ga variation).