Monodisperse nanoparticles via metal induced crystallization

Abstract

Articles you may be interested inPhotoluminescence properties and crystallization of silicon quantum dots in hydrogenated amorphous Si-rich silicon carbide films This paper discusses the self-assembled formation of monodisperse gold-rich nanoparticles and associated crystalline silicon nanostructures. Multilayer films comprising of amorphous Au 25 Si 75 and amorphous silicon were grown via dc magnetron sputtering and subsequently annealed under varying thermal conditions. The films were characterized by electron microscopy before and after the thermal anneal. Thermal decomposition of the multilayer films results in the metal induced crystallization of amorphous silicon, as well as the formation of uniform Au-rich nanoparticles. Further annealing did not alter the size or position of the nanoparticles, indicating that the particles are too small to induce further silicon crystallization. Through thermodynamic modeling, two mechanisms are shown to be viable means for nanoscaled size selection. The first mechanism entails crystallization of Au 25 Si 75 followed by metal induced crystallization of amorphous silicon, while the second utilizes spinodal decomposition of Au 25 Si 75 to select a single nanoparticle radius.

Growth of Straight Silicon Nanowires on Amorphous Substrates with Uniform Diameter, Length, Orientation, and Location Using Nanopatterned Host-Mediated Catalyst

“…Such possibility has been demonstrated in both microscale 33,34 and nanoscale. 34,35 However, in our case the (111) Si texture is not clear from XRD, probably because the layer is too thin (<13 nm) and embedded with some <5 nm Au particles precipitated from annealing (Figure 6c). As a result, the (111) crystal Au nanoparticles, together with the thin Si layer (expected (111) crystallized after the annealing with Au), seed the growth of Si NWs into AE111ae orientation and vertical to the substrate.…”

Templated control of Au nanospheres in silica nanowires

“…34 Also, Au nanoparticles have been shown to develop in just 30 minutes in a Si/Au system at 250 °C. 35 The size of the Au islands is similar on the Si micro-and nano-structured substrates since both had comparable amounts of Au deposited on their surfaces. Why then do the nanowires form exclusively on nanostructured substrates?…”

“…This is vapor liquid solid (VLS) growth because of the presence of the liquid reservoir on top of the nanowire; here the reservoir is consumed during nanowire growth and therefore does not act purely as a catalyst. Unlike size selection by metal-induced crystallization or amorphization which results in 1-2 nm particles, 35 this mechanism relies on metal-induced oxidation, with the resulting nanosphere size being set by a combination of the thermodynamically-controlled oxidation rate and the Si/Au ratio.…”

Gold nanoparticles via alloy decomposition and their application to nonvolatile memory

“…Earlier work has shown that amorphous Au x Si 100−x / Si sputtered multilayers, when annealed at 250°C, result in Au-rich nanoparticles and crystalline silicon nanowires. 11 Postanneal samples were oxidized using ultraviolet ͑UV͒-ozone oxidation. 12,13 This step was carried out by transferring samples from the deposition chamber into an in situ oxidation chamber where high-purity O 2 gas ͑99.999%͒ and UV light from a Hg lamp ͑wavelengths 185 nm and 254 nm͒ were introduced.…”