Thin Film Crystallisation Behaviours for Oxides of Rare-Earth Metals on Amorphous Silica

Abstract

Crystallisation behaviours of rare-earth metal oxides (REMO) were investigated. By electron beam evaporation of the rare-earth metals in O₂ at a pressure of (2 – 6)·10^-3 Pa their oxide films were obtained on SiO₂ films that served as substrates. Thin REMO films deposited on the amorphous silica surface without any special heating the substrate were amorphous. When the condensation temperature increased, crystallisation of REMO films began. for different REMO films the start of crystallisation was observed at a substrate temperature of 80 – 200°C. A characteristic of the initial crystallisation stages was the appearance of high-temperature REMO phases (monoclinic phase of Sc₂O₃, hexagonal phase of Gd₂O₃, Er₂O₃ etc.) alongside with the C-cubic form. for the C-cubic form a high degree of the coherent dispersion blocks texturing was typical. With a small increase in the condensation temperature, the high-temperature phases disappeared in the film, and crystallites reoriented. in increasing the condensation temperature, nanocrystallites rebuilt repeatedly in the film. This was accompanied with reorientation of film texture in the film growth direction. It seems that amorphous silica surface is to influence on the phase transitions at a growth boundary during the initial stages of the REMO film crystallisation.