Electrochemical behaviour of p Si in met

The mechanism of anodic dissolutions of p-Si single crystals in CH₃OH–LiCl and CH₃OH–LiCl–HCl solutions was investigated by means of the following electrochemical methods: linear sweep voltammetry, the potentiostatic transient technique, and XPS surface analysis. The dissolution of p-Si proceeds by a two-step mechanism with the creation of a Si(II) surface intermediate. At low anodic overvoltage, the dissolution proceeds with the formation of porous silicon, probably through the reaction: Si(II) → Si + Si(IV). Structural etching of the single crystal’s surface was observed at high anodic overvoltage (E > 2 V). At this potential, the concentration process involves the formation of a Si(IV) soluble product. Electrolysis of the methanol solvent containing Si(IV)M, where M = Pt, Cu, or 18/8 stainless steel, leads to the deposition of an amorphous organosilicon layer on the cathode. The analysis of the deposit performed by means of XPS, FTIR, and SEM allows determination of the morphology and composition of the film. The layer consists of Si–O–CH₃ compounds and can be created only in methanol solvent. The film is unstable in a humid atmosphere and undergoes transformation into a Si–OH layer.