Metal-Assisted Chemical Etching Using Tollen’s Reagent to Deposit Silver Nanoparticle Catalysts for Fabrication of Quasi-ordered Silicon Micro/Nanostructures

Abstract

Metal-assisted chemical etching (MacEtch) of semiconductor materials in HF/H 2 O 2 solution using noble-metal particles as catalysts has gained much attention in the past few years due to its unique properties. In this work, nanoscale Ag particles were deposited on (100) and (111) surfaces of polished p-Si wafers through the silver-mirror reaction. Subsequently these wafers were etched in 1:1:1 (v:v:v) HF(49%):H 2 O 2 (30%):EtOH solution at ambient temperature and pressure for 12 h, producing a number of different quasiordered silicon micro/nanostructures. The resulting surface-modified wafers exhibited mixed micro-and nanostructures that are an inherent feature of the etch process; for example, steps appear on the sidewalls of crystallographically defined nanopores, because the catalytic Ag nanoparticles are convected as they transit the developing pore during the etching process. The resulting materials exhibited much reduced reflectivity, reaching a maximum of 3.79 reduction near 330 nm, which renders them of interest in potential applications such as back-reflector templates for deposition of thin-film solar cell materials.

Comparisons of Fastness of the Coating Processes of Electroless Silver Plating on Polyethylene Membrane Surfaces

“…Fastnesses of the electroless silver plating processes of Tollen agent and then reducing agent on polyethylene membrane surfaces As a chemical reagent for electroless plating and consisted of the silver-amino complex solution of silver nitrate and ammonia, Tollen reagent could be precipitated of elemental silver in the presence of the aldehyde or alphahydroxy ketone groups in several organic matters on the PE membrane surfaces with a positive test of producing a characteristic "silver mirror" on the inner surfaces [1,3]. Besides being used to apply a silver mirror to glassware, Tollen agent could also be coated on the surfaces of many plastic applications (PE membranes) with the help of the processes of electroless plating reduced by glucose (an aldehyde).…”

“…For being freshly prepared in the laboratories, the Tollen reagent was not commercially available due to its short shelf life. It should be checked the utilities of the fastnesses of the electroless silver plating on PE membrane surfaces using Tollen agent firstly and then reducing agent [3].…”

“…Being called the reductants or reducers, the reducing agents in this experiment were complex compounds that could donate some electrons to the above-mentioned Tollen agent in the electroless silver plating reactions. The both strong (positive oxidation potential) and weak (negative oxidation potential) reducing agents typically in one of the lower possible oxidation states were oxidized by losing electrons with oxidizers of fewer electrons [3]. With the molecular formula C6H12O6 whose five hydroxyl (OH) groups were arranged in a specific way along the six-carbon back and known as the dextrose or grape sugar and one of the 16 aldose stereoisomers, D-glucose did occur widely in nature and be classed as a hexose of one sub-category of monosaccharides with 6 carbon atoms [25].…”

“…Fastnesses of the electroless silver plating processes of the mixed solution of Tollen agent and reducing agent on polyethylene membrane surfaces It was well known that the applications of silver mirror reactions requiring the highest optical qualities were occurred on cleaned and insulated surfaces such as PE membrane surfaces since it created nano-scale roughness and reduced the reflectivity when Tollen agent and D-glucose as reducing agent were put together in solutions [3,30]. The processes to produce silver mirrors by Tollen agent and Dglucose on PE membrane surfaces included additional additives to increase adhesion and film resilience.…”

“…Different from electroplating without use of external electric current through the solution and known as nongalvanic chemical plating, electroless plating in aqueous solutions is one of plating methods with several advantages versus electroplating such as free from flux-density and power supply issues providing an even deposit regardless of work-piece geometry and with the proper pre-plate catalyst depositing on non-conductive surfaces [1][2][3]. The several simultaneous electroless plating reactions are carried out when hydride ions from reducing agents (normally glucose) are released by producing negative charges on the solid substrates like the surfaces of the polymer plastics [4].…”