Measurement of atomic incorporation rates and modeling of surface reactions in (Ba, Sr)TiO3 films prepared by a liquid source chemical vapor deposition

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 (T-b) of 420-520 degreesC. The atomic incorporation rates of Ba, Sr, and Ti increased with increasing incident flux of each sou rce material, and subsequently the values became saturated. The activation energies E-a for the incorporated reactions were estimated using the Arrhen ius plots of the saturated values. The E-a values were almost the same for Ba, Sr, and Ti, and were about 1.5 eV. The values were almost independent o f the source supply ratios. From these experiments, we assumed a CVD model, where the precursors were transported onto the film surface and adsorbed t here with their own sticking coefficients. In the model, the sticking coeff icients of the Ba and Sr precursors (beta (Ba) and beta (Sr) respectively) were effected by the species of precursors adsorbed thereon. The values of beta (Ba) and beta (Sr) estimated from the experiments were about 1.0 x 10( -4) on the surface adsorbing Ti precursors, while they were about 1.0 x 10( -3) on the other surfaces, i.e., surfaces excluding those adsorbing Ti prec ursors. The atomic incorporation rates of Ba, Sr, and Ti were numerically s imulated, and were in good agreement with the experimental results for seve ral source supply ratios with different T-s values of 420-520 degreesC.