  We present models of electrodeposition of ZnO films with organic additives,
with focus on the growth of hybrid films with eosin Y. First we propose a rate
equation model which assumes that the additives form branches with an exposed
part above the ZnO deposit, growing with larger rate than the pure film, and
that the rate of production of ZnO near those branches is proportional to the
height exposed to the solution. This accounts for the production of OH- ions
near the branches and the reactions with Zn++ ions. The steady state solution
shows both species growing with the rate of the branches, and qualitatively
explains their catalytic effect. Subsequently, we propose a more realistic
statistical model for the formation of the hybrid deposits from Zn++ ions, a
hydroxide precursor and eosin in solution. Simple probabilistic rules are used
for reactions of eosin and oxygen, taking into account diffusion from solution
along the same lines of the diffusion-limited aggregation models. The catalytic
effect is represented by the preferencial production of OH- ions near eosin
branches, which form ZnO species. An improvement of the growth rate is possible
only with a rather large diffusion coefficient of eosin in solution compared to
that of hydroxide precursors, in agreement with experimental findings. In the
cases where a series of neighboring eosin clusters competitively grow, the
increase in the growth rate and the high eosin loading observed in the
simulated deposits also agree qualitatively with electrodeposition experiments.
