HIGH-RESOLUTION ELECTRON-MICROSCOPE OBSERVATION OF MEDIUM RANGE ATOMIC ORDERING IN AN AMORPHOUS PD-SI ALLOY

High resolution electron microscope images in amorphous Pd-Si alloy were calculated with various structure models and compared with the observed ones. For the structure models, atomic models of (1) dense random packing (DRP), (2) FCC atom clusters (embedded in DRP structure) and (3) icosahedral atom clusters (embedded in DRP structure) were constructed by using the Lennard-Jones type atomic potentials. Structure observations on the atomic level were made with a high resolution electron microscope at 200 kV for amorphous Pd80Si20 thin films deposited at 195 K by beam-sputtering technique. Atom clusters as large as 1-2 nm having the FCC-Pd type structure were observed locally. These FCC clusters are embedded in the structure which is thought to be that of DRP. A radial distribution function (RDF) calculated for the FCC cluster in the DRP structure was found to explain well the experimental RDF obtained by other reseachers for the amorphous Pd80Si20 alloy. © 1990, The Japan Institute of Metals. All rights reserved.