Towards more complex shapes of macroporous silicon

Macroporous silicon membranes, prepared by electrochemical etching, were subjected to pore widening performed either by multiple oxidation/oxide-removal cycles or by anisotropic etching in alkaline solutions. While multiple oxidations are used to obtain perfect cylindrical pores, the alkaline etching allows the fabrication of macropores with square and also, eight-sided (octagonal) cross-section. The shown post-etching treatment of macroporous silicon extends the possibilities of the electrochemical etching technique and enables the realization of 2D and 3D photonic structures with very complex geometries.