Orientation and Structure of Palladium Particles Formed by Evaporation on Alkalihalide Crystals

Abstract

The orientation and structure of palladium particles evaporated onto NaCl, KCl, KBr and KI cleaved in ultrahigh vacuum have been studied by electron diffraction and electron microscopy. It is concluded that the external shape of the epitaxial particles with the (001) orientation, showing a square shape, is generally an octahedron, although they have so far been considered to be a square pyramidal shape. The particles with the octahedral form grow at the nucleation stage, and then their shape changes gradually into a form truncated by six {100} faces in the subsequent stage. This shape is similar to Wulff polyhedron. The particles with the (001), (111) and (110) orientations have been observed. Furthermore, three kinds of the multiply-twinned particles of palladium have actually been observed on electron micrographs. Their particle sizes are generally very large as compared with those predicted by Ino.