Vapor-Liquid-Solid Growth and Properties of One Dimensional PbO and PbO/SnO2 Nanowires

PbO nanowires have been obtained via a self-catalyzed, vapor-liquid-solid mechanism and the reaction of Pb with O2 between 200°C and 300°C at 10 Pa. These had the form of tapes...

PULSE GROWTH OF THE GAAS NANOWIRES

The results of the simulation of the GaAs nanowire self-catalyzed growth via vapor-liquid-solid mechanism using various pulse modes are presented in this work.

Adjusting the Morphology and Properties of SiC Nanowires by Catalyst Control

We report on the growth of SiC nanowires on a single crystal Si substrate by pyrolysis of polycarbosilane and using two catalyst (Al2O3 and Ni) films with different thickness (2, 4, and 6 nm). The catalyst films were deposited on the Si substrate, and the SiC nanowires were grown according to two mechanisms, i.e., the oxide-assisted growth mechanism and vapor- liquid-solid mechanism. As a result, pearl-chain-like SiC nanowires and straight SiC nanowires were obtained. The prepared nanowires exhibited excellent photoluminescence properties, emission spectra displaying two emission peaks at 395 and 465 nm, and have good thermal stability below 1000 °C. The experimental results revealed the importance of the catalyst in controlling the morphology and properties of SiC nanowires.

Adjusting the Morphology and Properties of SiC Nanowires by the Catalyst Control

Herein, we report the growth of SiC nanowires on a single crystal Si substrate by pyrolysis of polycarbosilane and using two catalyst (Al2O3 and Ni) films with different thickness (2, 4, and 6 nm). The catalyst films were deposited on the Si substrate, and the SiC nanowires were grown according to two mechanisms, i.e., the oxide-assisted growth mechanism and vapor- liquid-solid mechanism. As a result, the pearl-chain-like SiC nanowires and straight SiC nanowires were obtained. The prepared nanowires exhibited excellent photoluminescence properties, the emission spectra displaying two emission peaks at 395 and 465 nm, and have good thermal stability below 1000℃.The experimental results revealed the importance of the catalyst in controlling the morphology and properties of SiC nanowires.

Greenockite Whiskers from the Bytom Burned Coal Dump, Upper Silesia, Poland

Orange greenockite (CdS) aggregates were found in a small fumarole at a burned coal dump near Bytom, Upper Silesia, Poland and were studied using a variety of techniques in order to determine their chemistry, morphology, and most importantly, the mechanism of crystal growth. Greenockite rods, wires, and whiskers with bismuth drops on crystal tops are predominant in these aggregates. Greenockite rods oriented sub-perpendicular to the substrate surface. The rod thickness reaches 5–6 μm and about 10 μm in length. The catalyst bismuth drop has a diameter comparable to the rod thickness. Fiber forms (wires and whiskers) are sub-parallel to the substrate surface. The thickness of these forms is usually less than 2 μm, and the length can be close to 1 mm. The bismuth drop diameter can show a large excess over the fiber thickness. Catalyst drops on the tops of whiskers began to change their form dynamically and exploded, spraying bismuth under the electron beam effect. Rods grow along the [01–10] direction, and whiskers and wires (axial forms) along the [0001] direction. Greenockite rod crystals, carrying on top a relatively homogenous bismuth catalyst drop, were formed on the heated substrate according to the VLS (vapor–liquid–solid) mechanism at temperatures not lower than 270 °C. Greenockite whiskers and wires grew just above of the substrate surface according to the VQS (vapor–quasiliquid–solid) mechanism at temperatures lower than 200 °C. These mechanisms of growth have very rarely been recorded to occur in nature and even less so in burning coal dumps. The cooperative growth effects of the fiber greenockite crystals were also described.

Кинетика роста зародыша из нанофазы

We present a theoretical analysis of the growth kinetics of a nucleus from a nano-sized mother phase with a restricted amount of material in the presence of the stopping effect due to the depletion of supersaturation. Such a regime is typical for GaAs nanowires grown by the vapor-liquid-solid mechanism from a Ga droplet and is observed by in situ growth monitoring inside a transmission electron microscope. An analytical solution is obtained for the time-dependent size of the nucleus and atomic concentration in a nano-phase. A principally new time-scale hierarchy is found, whereby the entire growth process id divided into 3 stages – (1) fast nucleus growth to the stopping size, (2) slow nucleus growth at the rate of refill of a mother phase, and (3) further refill of a mother phase to resume the initial supersaturation. A general criterion is formulated for observing the stopping effect depending on the size of a nano-phase.

Кинетика роста планарных нитевидных нанокристаллов

A kinetic equation is obtained which describes the elongation rate of planar semiconductor nanowires growing via the vapor-liquid-solid mechanism in the substrate plane. Theoretical analysis of different regimes depending on the nanowire radius and epitaxial conditions shows that planar growth of nanowires can be limited by either the Gibbs-Thomson effect in a catalyst droplet (for small droplet size) or surface diffusion of adatoms (for larger nanowire radii. Diffusion-like dependence of the growth rate on the nanowire radius R has the form R^(-m), where the power exponent equal 1, 3/2 or 2 depending on the mechanism of surface diffusion transport.