Role of Ag⁺ Ion Concentration on Metal-Assisted Chemical Etching of Silicon

Abstract

Abstract. Metal-assisted silicon etching in the HF/H2O2/H2O solution with silver ions as a catalyst was investigated. It is found that geometric parameters of layers of nanostructured silicon are determined by the silver-catalyst concentration. A spontaneous stop of the etching process at low Ag+ ion concentration is explained by formation of insoluble Ag2SiO3.

The Role of the Molecular Hydrogen Formation in the Process of Metal-Ion Reduction on Multicrystalline Silicon in a Hydrofluoric Acid Matrix

“…The widespread explanation of the molecular hydrogen formation resulted from a divalent reaction process [ 17 , 21 , 34 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ] in combination with the hydrogen-free reaction process during tetravalent valence transfer [ 11 , 12 , 15 , 21 , 34 , 40 , 41 , 44 , 55 ] may still fit, to some extent, based on the findings of example 2 of silver deposition. The results of the other metal depositions explained in Section 3.2 , Section 3.3 and Section 3.4 , especially the findings of platinum deposition, support a different and more complex theory for molecular hydrogen formation.…”

“…The unstable Si 2+ species [ 17 , 34 ] is subsequently converted by an H(+I)-based oxidant to the Si 4+ state (SiF 6 2− ) [ 17 , 34 ] with the formation of H 2 . There are different assumptions as to whether the oxidant is H + [ 36 , 37 , 38 , 39 ], H 2 O [ 34 ], HF [ 17 , 34 , 40 ] or the HF dissociation product HF 2 − [ 21 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ] (Equation (3)): …”

“…According to the most prominent theory, the course of the reaction changes from the divalent to the tetravalent mechanism when a certain current density is exceeded [ 17 , 34 ]. The bulk silicon is oxidized to Si 4+ and, subsequently, converted to the formal end product SiF 6 2− in the presence of F − [ 11 , 12 , 29 , 50 , 51 , 52 , 53 , 54 ], HF [ 15 , 21 , 34 , 41 , 44 , 55 ] or HF 2 − [ 21 , 44 ] with the intermediate formation of SiF 4 [ 34 , 40 ] without the formation of molecular hydrogen (Equation (4)): …”

“…Several series of experiments have been carried out based on HF solutions with Ag + , Cu 2+ , AuCl 4 − or PtCl 6 2− and multicrystalline silicon. The metal ions were chosen because they are commonly used in the metal-assisted etching of silicon [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 26 , 27 , 29 , 30 , 31 , 32 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 63 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , …”

Влияние типа и степени легирования на морфологию por-Si, полученного гальваническим травлением

“…Нанесение металла осуществляют либо вакуумным испарением [16], либо из раствора, содержащего ионы металла, которые мо-гут самопроизвольно восстанавливаться на поверхно-сти кремния, например ионы Ag + [17]. [20], в результате гальванического травления кремния на поверхности образуются микро-, мезо-и макропористые слои.…”