Study of amorphous alloy structures with medium range atomic ordering

Structures with atomic medium range order (MRO) extending as small as approximately 2 nm in amorphous alloys can be observed under suitable defocus conditions as clear lattice fringe images by means of axial-beam high-resolution electron microscopy (HREM). In this article, our studies of local structure observation in some metal-metalloid amorphous alloys with the "selected-defocus method" are introduced. Also introduced are an HREM image simulation study of amorphous alloy structures and a nano-probe (1-1.5 nm) electron diffraction analysis of MRO structure. A multislice image simulation study for suitable structure models (1) with a random atomic distribution, (2) with MRO regions having different sizes, distributions, and specimen thicknesses, is a necessary step to verify the MRO observation in amorphous alloys. It was demonstrated that not only HREM information but also nano-diffraction information are necessary in order to understand local structures of amorphous alloys.