COMPARATIVE TEM STUDY OF THE 3D LATTICE OF TELLURIUM NANOCLUSTERS FABRICATED BY DIFFERENT TECHNIQUES IN AN OPAL HOST

An electron-microscope study of synthetic opals containing tellurium i ntroduced into the regular void array either by melt injection or by e vaporation from solution is reported. In the first case, a three-dimen sional array of tellurium clusters interconnected by bridges was revea led. The clusters retain the same crystallographic orientation as one moves from one cluster to another. This suggests that cooling after in serting tellurium results in its directional crystallization, which is possibly controlled by the interconnecting channels. The second techn ique of tellurium introduction produces a nonuniform cluster array, wi th three-dimensional clusters growing not in all voids. The surface of most of the silica spheres is coated by a thin discontinuous layer of tellurium. This structure of the cluster array accounts for the nonli near current-voltage characteristic of the object as a whole. A possib ility of engineering cluster lattices differing in structural paramete rs has been demonstrated. (C) 1997 American Institute of Physics.