ion beam deposition (ibd) is the direct formation of thin films using a low-energy (tens of ev) mass-analyzed ion beam. the process allows depositions in which the energy, isotropic species, deposition rate, defect production, and many other beam and sample parameters can be accurately controlled. this paper reviews recent research at ornl on the ibd process and the effects of deposition parameters on the materials properties of deposited thin films, epitaxial layers, and isotopic heterostructures. a variety of techniques including ion scattering/channeling, cross-sectional transmission electron microscopy, scanning electron microscopy, and auger spectroscopy has been used for analysis. the fabrication of isotopic heterostructures of /sup 74/ge and /sup 30/si are discussed, as well as the fabrication of metal and semiconductor overlayers on si and ge. the use of ibd for low-temperature epitaxy of /sup 30/si on si and /sup 76/ge on ge is presented. the use of self-ion sputter cleaning and in situ reactive ion cleaning as methods for preparing single-crystal substrates for epitaxial deposition is discussed. examples of ibd formation of oxides and silicides on si at low temperatures are also presented