  In this paper we briefly review a model that describes the
diffusion-controlled aggregation exhibited by particles as they are deposited
on a surface. This model allows to understand many experiments of thin film
deposition. In the first part, we describe the model, which incorporates
deposition, particle and cluster diffusion, and aggregation. In a second part,
we study the dynamical evolution of the model. Finally, we analyze the effects
of small cluster mobility, and we show that the introduction of cluster
diffusion dramatically affects the dynamics of film growth. Some of these
effects can be tested experimentally.
