Etching anisotropy mechanisms lead to morphology-controlled silicon nanoporous structures by metal assisted chemical etching

Abstract

The etching anisotropy induced by the morphology and rotation of silver particles controls the morphology of silicon nanoporous structures, through various underlying complex etching mechanisms. The level of etching anisotropy can be modulated by controlling the morphology of the silver catalyst to obtain silicon nanoporous structures with straight pores, cone-shaped pores and pyramid-shaped pores. In addition, the structures with helical pores are obtained by taking advantage of the special anisotropic etching, which is induced by the rotation and revolution of silver particles during the etching process. An investigation of the etching anisotropy during metal assisted chemical etching will promote a deep understanding of the chemical etching mechanism of silicon, and provide a feasible approach to fabricate Si nanoporous structures with special morphologies.

Nanostructuring of Si substrates by a metal-assisted chemical etching and dewetting process

“…Lithographic methods are based on fabrication of desirable catalytic metal pattern. 1,12 Non-lithographic methods use various ways to depose catalytic metal into the form of a discontinuous layer, islands 7,8,10,13 or particles from a colloidal suspension. [14][15][16][17] Density of particles, islands and cracks in a metal layer determines whether the obtained structures are more like porous material or nanowires.…”

General corrosion during metal-assisted etching of n-type silicon using different metal catalysts of silver, gold, and platinum

“…16 Complex 3D structures, e.g. helical pores, 17,18 spiraling pillars created by grid-shaped and star-shaped catalysts, 19 nanocone arrays, 20 and zigzag wires, 21 have also been reported. We successfully enhanced the conversion efficiency of solar cells by using Si nanohole arrays.…”

“…etchant and Si wafer. 13,15,18,21,27,[31][32][33][34][35][36][37] Metal catalyst is also an important factor to change the porous structure. 25,26,[38][39][40][41] Lee at al.…”

Photoelectrochemical Characterisation on Surface‐Inverted Black Silicon Photocathodes by Using Platinum/Palladium Co‐catalysts for Solar‐to‐Hydrogen Conversion

“…This simplea pproach allowsf or advanced controlo ver the parameters of etching. For instance, generally the use of Au-MaCE [8] or Fe-MaCE [9] etchingf or 10-20 min resultsi nt he formation of highly ordered dense nanostructures of severalm icrons in length, whereas Ag-MaCE etching for the same period only results in meso-/nanoporouss ilicon, [10][11][12] or submicron lengths, [8,13,14] with required times up to 500 min to match the topologyo f that of Au-or Fe-MaCE. [5,13,15,16] However,t he interplay of a range of other factors, such as etchantconcentration,temperature and substrate type, determinet he resultant morphology.…”