ELECTRON-MICROSCOPIC STUDIES OF STRUCTURE AND CRYSTALLIZATION OF AMORPHOUS METAL-OXIDE FILMS

High-resolution transmission electron microscopy using axial beam illumination was carried out on vacuum-deposited WO3, TiO2, and MoO3 films. In as-deposited WO3 films thinner than 100 Å and films heated at 350°C for 2∼5 h which gave rise to amorphous haloes in electron diffraction, crossed fringe-like structure images of the order of 10∼20 Å was observed. This means that the amorphous films consisted of micro-crystallites in which the W–O6 octahedra were arrayed like crystalline WO3. When the films were heated at 350°C for 10 h, they grew to crystallites of WO3 as large as 100 Å. On the other hand, in WO3 films thicker than about 200 Å, crystals of a few microns grew after shorter heat treatment. Similar results were obtained for the TiO2 and MoO3 films. The differnce in crystallization between the very thin films and the thicker films is interpreted by considering the heat generated during crystallization and its dispersion. © 1979 The Japan Society of Applied Physics.