Stain etchants made from (HF+V(2)O(5)) or (HF+FeCl(3)center dot 6H(2)O+HCl or H(2)SO(4)) exhibited virtually no initiation time before the formation of porous silicon. Etching with Fe(III) solutions for extended periods resulted in a unique dual layer structure that can reach a thickness >10 mu m and exhibited not only red-orange but also green photoluminescence (PL). Etching with (CeF(4)+H(2)SO(4)) produced extremely uniform films. Visible PL was observed immediately after etching except for those films produced with (CeF(4)+H(2)SO(4)), which required several days of air exposure before bright and robust PL developed.
Electrochemical and Solid State Letters
Electrochemical Society Inc
Dudley, M. E., & Kolasinski, K. (2009). Stain Etching with Fe(III), V(V), and Ce(IV) to Form Microporous Silicon. Electrochemical and Solid State Letters, 12(4) http://dx.doi.org/10.1149/1.3074333