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

In-situ electrochemical characterizations together with ex-situ SEM observa tions have been used to characterize (111)-oriented p-Si surfaces after ele ctrochemical treatments known to lead to H incorporation into the Si lattic e. Prolonged cathodic polarization of Si substrates results in surfaces pre senting a large number of defects with regular triangular shapes, character istic of substrate orientation. These observations can be understood if p-S i is etched in 5% HF under cathodic conditions. It can be inferred that etc hing proceeds by H incorporation into Si, which creates subsurface and surf ace defects that are preferentially etched through a chemical mechanism. re sulting in the appearance of triangular pits.