Fabrication of ordered silicon nanopillars and nanowires by self‐assembly and metal‐assisted etching

Abstract

Silicon nanowires (SiNWs) and nanopillars have been obtained by metal-assisted etching (MAE), starting from silver thin films deposited by thermal evaporation and sputtering on silicon substrates. Different deposition methods and thickness are strongly affecting spatial distribution and shapes of the extruded silicon nanostructures. The paper reports a study of distribution and morphology, as a function of silver thickness, deposition conditions and etching times. The application of polystyrene soft masks obtained by self-assembly and the sputter-etching by Ar ions allow the formation of regular indentations in the silver thin films, giving origin to a regular distribution of extruded pillars and wires during the following etching in HF:H2O2:H2O. The aqueous etching and the use of silver still influence the homogeneity of the etching result on large area and introduce a modulation in the etching front, so\ud affecting thickness homogeneity. Work is in progress to replicate these former results with gold and different etching solutions

Electrical Contacts on Silicon Nanowires Produced by Metal-Assisted Etching: a Comparative Approach

“…The techniques used to synthesize nanowires are many, and among all, our study refers to the combination supramolecular self-assembly of polystyrene nanospheres and metal-assisted chemical etching (MACE) [ 11 , 12 ], a technique based on electroless etching of silicon in the presence of a noble metal acting as a catalyst [ 13 ]. With this approach, it is possible to fabricate ordered wires with a well-defined diameter and spatial distribution.…”

Macro and quasi‐mesoporous silicon by self‐assembling and metal assisted etching

“…This structure is then propagated to the silicon substrate by metal assisted etching, with time ranging from 30 s to 1 min at 60 °C in a solution of HF:H 2 O 2 :H 2 O 22%:9%:69% in volume 8, 12.…”

Sub-Parts Per Million NO2 Chemi-Transistor Sensors Based on Composite Porous Silicon/Gold Nanostructures Prepared by Metal-Assisted Etching

“…This augmented etching rate is due to the increasing physical access of the etchant to the area 31 underneath Au nanoislands (active site), which is related to the increase of grain size and coalecence of gold NPs and, in turn, determined by the augmented thickness of metal film deposited. 21,37 By further increasing Au thickness, cSiAuN depth becomes slightly dependent on both size and distribution of metal NPs and the depth-thickness curve tends to saturate around 2 μm of pore depth (Figure 1g). Such a behavior can be explained by considering that the catalytic activity of Au nanoparticles has been demonstrated to be very sensitive to the ratio between Au particle size and Au/semiconductor perimeter interface.…”

“…19 Here we propose a facile and effective top-down method for the high-yield fabrication of chemi-transistor sensors making use of composite porous silicon/gold nanostructures (cSiAuNs) acting as sensing gate. In particular, we investigate the integration of cSiAuNs synthesized by metal-assisted etching (MAE), 20,21 using gold NPs as catalyst, in solid-state junction-field-effect transistors (JFETs), aimed at the detection of NO 2 down to 100 parts per billion (ppb). The chemitransistor sensors, namely cSiAuJFETs, operate at room temperature and are reliable, sensitive, and fully recoverable for the detection of NO 2 at concentrations between 100 and 500 ppb, up to 48 h of continuous operation.…”