Interfacial layer formation in Gd2O3 films deposited directly on Si(001)

Gd2O3 films were deposited on Si(0 0 1) substrates using electron-beam evaporation from pressed-powder targets. Near the surface of the films the composition is stoichiometric, according to the results of X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering measurements. Thermal stability of the films was evaluated in a series of samples annealed in O-2 between 500 and 780 degreesC. Transmission electron microscopy reveals a complicated multilayer structure even in the as-deposited film. The thicknesses of the constituent layers change with annealing, and the reaction depends on the annealing temperature. X-ray reflectivity was used to verify the layer thicknesses and to determine their composition. An SiOy layer was identified, as well as an intermediate, mixed (SiO2)(x)(Gd2O3)(1-x) layer, The silicon dioxide fraction (x) increases with annealing temperature, reaching the value of 33% in the most extreme case. XPS and Auger depth profiling were used to gain additional insight into the elemental composition and to verify the bonding of the constituent species, The SiOy layer forms a good electrical interface with the substrate, but reduces the dielectric constant of the film. (C) 2001 Elsevier Science B.V. All rights reserved.