The synthesis of matrices of embedded semiconducting nanowires

Abstract

In this work we report how single crystal nanowires can be assembled into regular arrays using mesoporous thin films to define the architecture. Mesoporous thin films were prepared by a sol-gel method. These provide films of very regular structure and dimensions. The films produced in this way have almost single crystal like structures and can also exhibit strong epitaxy to the underlying silicon substrate. The films are subjected to a supercritical fluid (SCF) environment in which a precursor is decomposed to yield nanowires of metals, semiconductors or oxides. Using these SCF conditions, pore filling is complete and the products are nanowires which are single crystals and structurally aligned in one direction. The growth mechanism of the nanowires is described and size effects discussed.

Ordered Mesoporous Silicate Structures as Potential Templates for Nanowire Growth

“…In previous work we have shown that the supercritical-fluid method can be used to develop nanowires within the pore structure. [4,9] Furthermore, the use of supercritical CO 2 to deposit metal species into the pore has been seen to cause minimal disruption to the porous structure and this is confirmed here. A TEM image of the sample surface (Fig.…”

“…We have used mesoporous powders and thin films as templates for nanowire growth. [4,7,9,10] Along with many authors we have shown that very regular MTFs can be produced at surfaces. [11] The synthesis of highly organized ordered domains using patterned substrates with adjustable dimensions has proved very successful.…”

“…However, the appearance of sharp features is consistent with the formation of 1D nanowires of this diameter. [4,9,10] Energy dispersive X-ray (EDX)…”

Containing the catalyst: diameter controlled Ge nanowire growth

“…11,15 This same technique has been used to make metallic nanowires of cobalt, copper and iron oxide 16 and has even been extended to the growth of Ge nanowires within mesoporous silica hosts. 12,13 Anodic alumina membranes (AAMs) have also been used to template the growth of Ge nanowires using both batch and injection ow-through SCF experiments. 10 In these experiments, Au colloids were used as growth catalysts inside the AAMs and the ow-through methods were found to produce better quality Ge nanowires compared to batch reactions.…”

“…9 Various templated growth methods have been employed for growing small diameter Ge nanowires (<15 nm), including the use of anodic alumina oxide and silica membranes. [10][11][12][13] The high-diffusivity of a supercritical uid enables rapid transport of precursors into the pores of many templates, permitting swi nucleation and growth of nanowires. Control over the pore geometry of templates has subsequently allowed the aspect ratio and optical properties of the included nanowires to be controlled with excellent precision.…”