The Dependence of Silicon Reactivity on the Constituents of the Etchant Electrolyte and the Effect of Some Postetch Treatments on the Photoluminescence Properties of Porous Silicon

The cyclic voltammetry (C.V.) technique was used to study the electrode
process of silicon in different etchant electrolytes. Also, similar anodizing
solutions to the electrolytes used in the C.V. were used for fabricating porous
silicon (PS) samples in the electrochemical cell and the effect of some postetch
treatments on the photoluminescence (PL) properties of these PS samples were
tested. The j-v relation showed that, up to ≈ 50% water in the etchant
electrolyte, the critical current peak height in HF:HCl:C2H5OH: H2O
electrolyte is higher than the critical current peak height in HF:(CH3)2CO:H2O
electrolyte, which is higher than the peak in HF:C2H5OH:H2O electrolyte. Also,
the j-v relation in case of concentrated electrolytes (≈0.4 % water) was not the
standard one for PS formation. These results were reflected in the PL
properties of the fabricated PS samples. Water in the presence of HF had a
magnified influence in the PL intensity of PS samples fabricated via anodization
in concentrated electrolyte. A mechanism for Si dissolution in HF-acetone was
proposed. The results were explained in terms of the model which attributes the
PL to surface confined molecular emitters.