Epitaxial growth and surface morphology of aluminum films deposited on mica studied by transmission electron microscopy and atomic force microscopy

The bulk structure and epitaxial growth of aluminum films deposited on mica substrates by thermal evaporation in a wide temperature range (16-550 degrees C) in high vacuum were investigated by transmission electron microscopy and transmission electron diffraction. The surface morphology of the films was observed and analyzed by atomic force microscopy. The films prepared at room temperature consist of single crystals having a diameter of 90 40 nm with (111) planes. The surface of the films comprises spherical grains with morphology that is caused by self-shadowing during the deposition. The surface of the films becomes smoother as the temperature increases, and atomically-smooth surfaces with a root-mean-square roughness of about 0.45 nm over an area of 1 mu m(2) are obtained at 250-350 degrees C. The crystals are oriented randomly along the [111] direction perpendicular to the substrate. The surface of the films consists of larger (> 300 nm) grains with terraces, and the surface becomes rough above 400 degrees C. Films with well-oriented single crystals along the [111] direction perpendicular to the substrate are obtained above 520 degrees C. The films grown epitaxially at 520-550 degrees C are characterized by the isolated grains with a diameter of 1220 +/- 450 nm. (C) 2007 Elsevier B.V. All rights reserved.