We have investigated hydrogen diffusion in hydrogenated ͗100͘ Si/ Si homoepitaxial structures, which were grown by molecular beam epitaxy at various temperatures. The substrate growth temperature can significantly affect the H diffusion behavior, with higher growth temperatures resulting in deeper H diffusion. For the Si/ Si structure grown at the highest temperature of 800°C, H trapping occurs at the epitaxial Si/ Si substrate interface, which results in the formation of ͑100͒ oriented microcracks at the interface. The mechanism of H trapping and the potential application of these findings for the development of a method of transferring ultrathin Si layers are discussed.