The structure and properties of thin solid films deposited in vacuum can be influenced substantially if additional energy and momentum is provided to the growing layers by energetic, inert or film-forming species. Various ion beam configurations for investigating these effects are discussed. Recent results are presented in conjunction with the following special film structures: (1) epitaxial, graphoepitaxial, and hydrogenated amorphous silicon deposits; (2) hard and unusual films of carbon and of boron nitride. Though the basic structure of the latter films is quasi-amorphous, microcrystals of high-pressure phases could be detected. Further trends are outlined.