A process for forming a thin film of a given material includes providing a first substrate having, on the surface, an amorphous and/or polycrystalline film of the given material and a second substrate is bonded to the first substrate by hydrophobic direct bonding (molecular adhesion), the second substrate having a single-crystal reference film of a given crystallographic orientation on the surface thereof. A heat treatment is applied at least to the amorphous and/or polycrystalline film, where the heat treatment causes at least a portion of the amorphous and/or polycrystalline film to undergo solid-phase recrystallization along the crystallographic orientation of the reference film, where the reference film acts as a recrystallization seed. The at least partly recrystallized film is then separated from at least a portion of the reference film.