The morphology of anodized p-type Si with the native oxide formed between t
he back surface of Si and the back metal was studied. Anodization of p-type
Si having a 4.2 Angstrom native oxide laver resulted in the formation of a
pproximately rectangular parallelepiped macropores with pore size of 1-3 mu
m followed by needlelike structures with diameter of 1.7 mum and finally th
e mirror surface. with an increase of the current density.