Figure 1: A schematic depiction illustrating the electroless deposition of silver on silicon in HF/AgNO3 solution and the silver-nanoparticle-catalyzed chemical etching of silicon in HF/Fe(NO3)3 solution. (a-c) Nucleation and growth of silver nanoparticles on the silicon surface in HF/AgNO3 solution: SiO2 forms simultaneously underneath the silver nanoparticles, and pits form as a result of etching away of SiO2 in HF solution. (d-f) Reduction of Fe3+ ions, etching of silicon, and sinking of silver nanoparticles in HF/Fe(NO3)3 solution: deeper pits are created by the silver nanoparticles. (g) Silver nanoparticle arrays form on the silicon surface. (h) Deep pores form in the bulk silicon in HF/Fe(NO3)3 solution as a result of the continuous etching away of SiO2 underneath the silver nanoparticles [36].