Pit formation on p-Si during hydrogen evolution in HF electrolyte

In-situ electrochemical characterizations together with ex-situ SEM observations have been used to characterize (111)-oriented p-Si surfaces after electrochemical treatments known to lead to H incorporation into the Si lattice. Prolonged cathodic polarization of Si substrates results in surfaces presenting a large number of defects with regular triangular shapes, characteristics of substrate orientation. These observations can be understood if p-Si is etched in 5% HF under cathodic conditions. It can be inferred that etching proceeds by H incorporation into Si, which creates subsurface and surface defects that are preferentially etched through a chemical mechanism, resulting in the appearance of triangular pits.