We report on the microstructure of silicon coimplanted with hydrogen and helium ions at moderate energies. X-ray diffraction investigations in as-implanted samples show the direct correlation between the lattice strain and implanted ion depth profiles. The measured strain is examined in the framework of solid mechanics and its physical origin is discussed. The microstructure evolution of the samples subjected to intermediate temperature annealing (350 ° C ) is elucidated through transmission electron microscopy. Gas-filled cavities in the form of nanocracks and spherical bubbles appear at different relative concentration, size, and depth location, depending on the total fluence. These different microstructure evolutions are connected with the surface exfoliation behavior of samples annealed at high temperature (700 ° C ) , determining the optimal conditions for thick layer transfer. 1.5 μ m thick Si films are then obtained onto glass substrates.