Role of hydrogen in the separation of a porous Si layer in a layer transfer process

The role of hydrogen in a recently developed one-step method for the formation and separation of a thin porous Si film from the initial Si substrate is investigated by means of Raman spectroscopy and detailed morphological analysis. It is shown that hydrogen plays a crucial role in the formation and separation of the porous Si film. Micro-Raman spectroscopy reveals that hydrogen in molecular form is accumulated in the micropores and creates hydrodynamic pressure which could be strong enough to break the thin pore walls in a high-porosity layer. As a result the upper porous Si film is separated from the original substrate. The kinetics of the process is confirmed by transmission and scanning electron microscopy.