The chemical and physical interactions of ions with surfaces in the energy range 5 eV to several keV will be described. Hyperthermal reactive ions impinging on surfaces provide a method for deposition/growth/synthesis of materials within a unique nonequilibrium UHV environment, giving rise to the technique of ion beam deposition (IBD). IBD allows independent control over parameters such as ion energy and type, ion fluence and dose, substrate temperature, and background gases. The depth of penetration/interaction of the impinging ions with the surface is determined by the ion kinetic energy. The excellent control over ion dose allows deposition of thin films, e.g. < 30 @Ao@, with sharp film-substrate interfaces. The UHV conditions in the sample chamber allow deposition onto atomically clean and well-ordered surfaces. In situ diagnostic techniques, such as reflection high energy electron diffraction (RHEED), x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), mass spectrometry, and a microbalance allow direction characterization of the deposited/reacted layers. Examples of the use of mass- and energy-selected beams for hyperthermal surface reactions, film growth, and shallow implantation will include: Si+ ion homoepitaxy, growth SiO2 and TiSi2 films on silicon, growth of Ti and TixAlyOz films on sapphire (a-Al2O3), controlling cationic diffusion coefficients in sapphire, and interactions of chlorotitanium ions TiClx+ with graphite and silicon surfaces.