Ion beam deposition is a process far from thermodynamic equilibrium and is in particular suited to grow metastable thin films with diamond‐like properties, such as tetrahedral amorphous carbon (ta‐C) and cubic boron nitride (c‐BN). In this contribution the atomistic description of the deposition and growth processes are reviewed and compared to experimental results, obtained from mass selected ion beam deposition. The focus will be set to the nucleation and growth processes of boron nitride as a model system for ion based thin film formation. Furthermore, recent examples for nanostructure formation in ion deposited compound thin films will be presented. Ion beam deposited metal‐carbon nano‐composite thin films exhibit a variety of different morphologies such as rather homogeneous nanocluster distributions embedded in an a‐C matrix, but also the self‐organized formation of nanoscale multilayer structures. © 2004 American Institute of Physics