Mechanical properties of vertically aligned single-crystalline silicon nanowire arrays

Abstract

Single-crystalline p-type silicon nanowire (SiNW) arrays have been formed by electroless metal deposition on a silicon wafer piece in an ionic Ag/fluorhydric acid (HF) solution through selective etching. They display mechanical properties that are different from those of both bulk silicon and single SiNWs. As any practical application of these materials is likely to involve a large number of nanowires in close proximity to each other, it is necessary to understand the mechanical properties of SiNW arrays. In this work, as a first step to characterize their mechanical properties, the buckling instabilities of the surfaces formed by vertically aligned SiNWs have been studied by nanoindentation tests.

Fully Tunable Silicon Nanowire Arrays Fabricated by Soft Nanoparticle Templating

“…Nanoscale patterning is widely used across disciplines to impart new functions and properties to materials. Arrays of vertically aligned silicon nanowires (VA-SiNWs) are a prominent example where control of both their crystallographic structure (i.e., growth direction) and of their geometrical parameters (diameter, height, and spacing) enables the emergence of different photonic, − electronic, mechanical, wetting, and biointerface properties , compared to the bulk material. These include increased optical absorption due to light trapping, generation of structural colors due to wave-guiding and resonance phenomena, ,,, high density of nanowire field-effect transistors (FETs), and the ability to transfect cells in vitro and in vivo. ,, Future nanowire-based device technology requires an economically viable path toward high-throughput, robust, and scalable processing, and ideally the ability to fabricate VA-SiNW arrays with precise control of their geometrical parameters.…”

Sarcosine Prostate Cancer Biomarker Detection by Controlling Oxygen in NiOx Membrane on Vertical Silicon Nanowires in Electrolyte–Insulator–Nanowire Structure

“…The areal density of nanowires is 5.71 μm –2 , which is higher than the reported density value of 3.6 μm –2 . Owing to this higher areal density of the nanowires with respect to planar sensors, sarcosine sensing ability is enhanced 1000 times more than the planar substrate.…”

“… The time-dependent lengths of SiNWs are shown (Figure S3) and estimated using eq below: where “ l ” is the length of NWs, “ t ” is the etching time, l max is the average maximum length of 24.426 μm, “α” is a constant with a value of 6/5, “β” (= 1/ t sat ) is a constant, and “ t sat ” is the saturation time. Several groups have reported different values of length and diameter of the NWs in other conditions. ,− Etching with longer time causes the bundling up of the NWs on some places (Figure D). When the length is much larger than the proper ratio of NW diameter, the mechanical strengths get weakened and well-separated NWs are not to be observed. ,, The nanowires have a rough surface, and they are ribbon-type (Figure S4), which is also beneficial to increase pH sensitivity as well as surface-site activity.…”

“…A certain gap is maintained between the nanowires corresponding to the deposited Ag particles. The chemical etching mechanism is well-known. − However, it is observed that synthesis at room temperature (RT) is better than elevated temperature (Figure S1) because the number of free-standing NWs is few and they are vertical over the wafer (Figure C).…”

“…The areal density of nanowires is 5.71 μm −2 , which is higher than the reported density value of 3.6 μm −2 . 31 Owing to this higher areal density of the nanowires with respect to planar sensors, sarcosine sensing ability is enhanced 1000 times more than the planar substrate. To reduce the sample volume and to detect at shorter time, a drop of mixture (Tris plus SOx plus sarcosine) is used and kept on the sensing area.…”