Over-etching at the edges of the mask during local macropore formation. The electrochemical etching was performed in low-doped n-type silicon (30 Ω cm) under potentiostatic control (4 V/CE) for 3 h under 130-W backside illumination. The electrolyte was composed of HF (2.4 wt.%) and CTAC (120 ppm).
Defforge et al. Nanoscale Research Letters 2012 7:344 doi:10.1186/1556-276X-7-344