This interdisciplinary book brings together researchers from a wide range of scientific fields to offer insights into the nature of polycrystalline thin films. These films have properties that are different from those of a bulk polycrystal and from those of a single crystal film. In particular, the volume focuses on film deposition and processing techniques which allow the fabrication of films with innovative microstructures and technologically relevant properties. The work presented ranges from theoretical studies to technological applications. Topics include: microstructural evolution; interfaces and mechanical properties; characterization of microstructure; hard and refractory films; polycrystalline silicon; electrical properties; optical properties; gas sensors; ferroelectric films; metallization; and magnetic and MEMS applications.