Drying induced self-formation of semi-ordered nano-porous silicon micro-hairs

Spontaneous drying induced self-transformation of highly-porous Si layers into oriented micro-tubular hairs is reported. Main mechanisms involved in such a self-formation of the porous silicon hairs are analyzed: the large capillary stresses at the liquid evaporation from the pores during the drying process, existence of lateral in-plane stresses at the interface "PS layer - bulk Si substrate", engineering of in-depth mechanical stress gradient and preferential cracking of the porous layer along the [110] and [1$ \bar 1 $0] directions.