Control of mesoporous silicon initiation by cathodic passivation

• Cathodic polarization was applied before and during mesoporous silicon formation.
• We characterized the effect on pore size and pore density at the surface.
• The cathodic treatments significantly change the surface morphology.
• These effects are explained by the cathodic passivation of {100} silicon surfaces.

We demonstrate that cathodic polarization is an effective method for in-situ control of surface morphology in the fabrication of mesoporous silicon. The cathodic currents are applied on the silicon electrode before or during the anodic formation of mesoporous silicon. On the surface, the formation of a parasitic microporous layer is avoided, the pores diameter can be increased from 5 to 32 nm, and the pore density can be decreased from 1900 to 600 μm− 2. A simple growth model is proposed to explain the surface morphology evolution based on the hydrogen passivation of the silicon surfaces in the cathodic regime.