PREPARATION OF THIN NANOPOROUS SILICON LAYERS ON N-SI AND P-SI

The formation of thin nanoporous Si layers on n- and p-Si(lll) was inv estigated with field emission scanning electron microscopy for prepara tion in aqueous NH4F solutions with pH 3.2 and 3.8. It was shown that very thin homogeneous nanoporous Si layers can be prepared on both n- and p-Si substrates in a well-controlled manner. The thickness of the nanoporous Si layers was limited by corrosion reactions and could be c hanged from about 20 nm to 180 nm depending on flowed charge, the conc entration of the solution and the anodization current.