Measurement of Atomic Incorporation Rates and Modeling of Surface Reactions in (Ba, Sr)TiO3 Films Prepared by a Liquid Source Chemical Vapor Deposition

Abstract

Atomic incorporation rates in (Ba, Sr)TiO3 [BST] films prepared by a liquid source chemical vapor deposition (CVD) method were measured using an X-ray fluorescence (XRF) method for several source supply ratios with different substrate temperatures (Ts) of 420–520°C. The atomic incorporation rates of Ba, Sr, and Ti increased with increasing incident flux of each source material, and subsequently the values became saturated. The activation energies Ea for the incorporated reactions were estimated using the Arrhenius plots of the saturated values. The Ea values were almost the same for Ba, Sr, and Ti, and were about 1.5 eV. The values were almost independent of the source supply ratios. From these experiments, we assumed a CVD model, where the precursors were transported onto the film surface and adsorbed there with their own sticking coefficients. In the model, the sticking coefficients of the Ba and Sr precursors (βBa and βSr, respectively) were effected by the species of precursors adsorbed thereon. The values of βBa and βSr estimated from the experiments were about 1.0×10-4 on the surface adsorbing Ti precursors, while they were about 1.0×10-3 on the other surfaces, i.e., surfaces excluding those adsorbing Ti precursors. The atomic incorporation rates of Ba, Sr, and Ti were numerically simulated, and were in good agreement with the experimental results for several source supply ratios with different Ts values of 420–520°C.