Hydrogen platelets in crystalline silicon - precursors for the `smart cut'

High concentrations of H in crystalline Si are known to induce planar defects (platelets), primarily in the (100) and the (111) planes. These platelets are precursors for the so-called `smart cut' technique for fabricating Silicon-On-Insulator (SOI) structures. The atomic-scale mechanisms for the nucleation and growth of the H-induced platelets and many other experimental observations have remained elusive. We review recent extensive first-principles calculations in terms of which a comprehensive picture of platelet nucleation and growth has emerged. The theory naturally accounts for the observed preference for (111) and (100) planes, for H release and trapping of H₂ molecules, and other observations. The platelets are arrays of second-neighbor hydrogenated vacancies that do not bind to each other, but their formation is due to energetically preferred reaction pathways.