Self-assembled mesoporous silicon in the crossover between irregular and regular arrangement applicable for Ni filling

Porous silicon (PS) channels fabricated during an electrochemical anodization process in hydrofluoric acid solution, without pre-structuring, normally arrange in an irregular morphology. In this work self-organized quasi-2D regular pore arrangements have been fabricated by accurate mutual control of various process parameters. Self-organized pore formation can be tailored and periodic pore arrangements are possible. A particular parameter to vary the inter-pore spacing is mainly the HF concentration, whereas the pore diameter primarily depends on the current density. The well-separated pores are highly oriented perpendicular to the surface and the pattern of self-organized pores is quadratic like due to the (1 0 0)-crystal orientation of the wafer. The isolated pores show little dendritic growth and their diameter can be tuned between 10 and 100 nm, thus belonging to the meso-porous up to the macro-porous regime. The pore growth occurs in an anisotropic manner which means that the channels grow significantly faster in (1 0 0) direction than in (1 1 1) direction. Into this self-assembled PS template metallic Ni is deposited using an electrochemical deposition step which results in a PS/Ni-nanocomposite with potential for applications as magnetic and magneto-optical devices. The filling process is performed under cathodic conditions and could be refined by pulsed current charging.