High fluence H implantation in Si and Ge results in the formation of extended planar defects, the H-Induced Platelets (HIP), which are known to be the precursors for the layer splitting process via ion cutting. Although HIP have been largely investigated both experimentally and theoretically, many questions about their structure remain unanswered. In particular, it is not clear whether vacancies (V) are required for forming HIP, and how H interacts with the native atoms.

(001) Ge was implanted with H and the as-induced (001) HIP were studied by HRTEM (0.19 nm point resolution). Their typical size being of a few nanometers and the interpretation of the HRTEM contrast being not straightforward, coupling with image simulations and first-principles atomistic calculations appears to be the only relevant approach to determine the atomic structure of the defects. A large set of possible configurations were considered, including various numbers of vacancies and H₂ molecules in the core of the defect. Low energy configurations were then introduced into a larger model, which was compared with HRTEM images. The most favorable configuration involves a dihydride passivation, the presence of vacancies, and a filling of the formed cavity with H₂ molecules. The presence of dihydrogen molecules into the platelet leads to a dilation of the surrounding layers, with a calculated maximum amplitude of 0.6 Å, in agreement with the lattice shifts measured on both the HRTEM micrographs and the image simulations. These results suggest that the atomic species (H, V) involved in the formation of (001) and {111} HIP are different. High resolution Z‑contrast, under progress, is expected to provide an experimental determination of the number of vacancies involved in the HIP formation.