Synthesis Of Si Nanowires Research Articles

Growth study of silicon nanowires by electron microscopies

We present a method that allows the synthesis of silicon nanowires (Si NWs) using Au or Ga as catalyst solvent in a scanning electron microscopy. The method is based on localized joule heating of tungsten wires to activate vapor–liquid–solid Si nanowire synthesis. Directly from scanning electron microscopy images we observe two different growth mechanisms for each catalyst solvent (Au and Ga). Since the conductive tungsten wires can be elaborated by focused ion beam induced deposition on 50-nm-thick Si 3N 4 membranes, we will show that transmission electron microscopy characterizations can be deduced from as-deposited .silicon nanowires.

Fe-Assisted Synthesis of Si Nanowires

Ultrafine and pure Si-nanowires (SiNWs) have been synthesized with the assistance of carbon nanotubes (CNTs) during a chemical vapor deposition process via the vapor liquid solid (VLS) mechanism. A mixture of CNTs and Si3N4 produces a high yield of fine SiNWs upon heating at 1600 °C under Ar atmosphere. Fe nanoparticles, located at the tip of CNTs, have been employed as a catalyst for the growth of nanowires and carbon acted as a reducing agent during the synthesis process. The resulting SiNWs have been appraised by SEM, TEM, XRD, Raman, BET, and FTIR to investigate the morphology, structure, and surface characteristics. Electron microscopic studies have demonstrated that the SiNWs have a uniform diameter of 7−17 nm, being single crystalline and enveloped with a tiny sheath of SiOx (x = 1∼2). Furthermore, hydrofluoric acid etching can remove the oxide shell, leading to much purer and finer SiNWs. Nitrogen-sorption isotherms indicate that SiNWs have very high BET specific surface areas. The high yield, ult...

Synthesis of Si nanowires with a thermally oxidized shell and effects of the shell on transistor characteristics

Silicon nanowires (SiNWs) with a single-crystalline Si core and a thermally oxidized shell (core-shell SiNWs) were synthesized by gold-catalyzed chemical vapor deposition followed by rapid thermal oxidation. To synthesize high-quality core-shell SiNWs, the relationship between the growth parameters and the crystallinity was studied. Furthermore, the formation process of the oxide shell was analyzed in detail by transmission electron microscopy. Using SiNWs as channels, back gate-type field effect transistors (FETs) were fabricated on p-type silicon wafers. FETs with core-shell SiNWs channels exhibited smaller hysteresis in the drain current ( I d ) vs. gate voltage ( V GS ) characteristics and higher on/off drain current ratio ( I ON/I OFF ) than those with bare SiNWs channels.

In Situ Laser Synthesis of Si Nanowires in the Dynamic TEM

The dynamic transmission electron microscope (DTEM) is introduced as a novel tool for in situ nanowire (NW) synthesis and characterization. Initial results show crystalline Si NW production by a root-based growth mechanism using a pulsed laser ablation (PLA) method inside the microscope column (see image). The potential of the DTEM to characterize the evolution of nanostructures by PLA methods is demonstrated.

Ultrafast synthesis of Si nanowires by DC arc discharge method and morphology control

Silicon nanowires (SiNWs) have been synthesized by a facile direct current (DC) arc discharge method. The SiNWs have homogeneous diameters of 10–20 nm and lengths ranging from several ten nanometers to several microns. Each SiNW interconnects with a metal nickel as catalyst. Morphology control of the products can be easily achieved by adjusting the current and the voltage of the discharge. X-ray diffractometer (XRD), field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM) and Selected-area electron diffraction (SAED) were used to study the structures and the morphology of the SiNWs. SiNWs were polycrystalline, which confirmed by XRD and SAED. The formation mechanism of SiNWs generally attribute to the presence of Ni catalysts in the synthesis process of vapor–liquid–solid (VLS).

Si nanowires synthesized with Cu catalyst

The metal copper which is a newly developed interconnecting material for integrated circuit (IC) has been used as the catalyst to catalyze the formation of the Si nanowires in high temperature tube furnace. The growth direction of the straight Si nanowires is <111> and the polyhedron η″-Cu 3Si alloy is on the tip of the Si nanowires. The synthesis temperature of the Si nanowires is 500 °C. Such a low temperature implies that the vapor–solid (VS) should be the growth method. The cheap Cu catalyst is favorable for the mass synthesis of Si nanowires.

Uniformly Sized Gold Nanoparticles Derived from PS-b-P2VP Block Copolymer Templates for the Controllable Synthesis of Si Nanowires

A monolayer of gold-containing surface micelles has been produced by spin-coating solution micelles formed by the self-assembly of the gold-modified polystyrene-b-poly(2-vinylpyridine) block copolymer in toluene. After oxygen plasma removed the block copolymer template, highly ordered and uniformly sized nanoparticles have been generated. Unlike other published methods that require reduction treatments to form gold nanoparticles in the zero-valent state, these as-synthesized nanoparticles are in form of metallic gold. These gold nanoparticles have been demonstrated to be an excellent catalyst system for growing small-diameter silicon nanowires. The uniformly sized gold nanoparticles have promoted the controllable synthesis of silicon nanowires with a narrow diameter distribution. Because of the ability to form a monolayer of surface micelles with a high degree of order, evenly distributed gold nanoparticles have been produced on a surface. As a result, uniformly distributed, high-density silicon nanowires have been generated. The process described herein is fully compatible with existing semiconductor processing techniques and can be readily integrated into device fabrication.

Investigation of the growth process of Si nanowires using the vapour-liquid-solid mechanism

Silicon nanowires have been grown by the thermal decomposition of silane via the vapour-liquid-solid (VLS) mechanism. Three different stages of VLS growth (eutectic alloy formation, crystal nucleation and unidirectional growth) were studied separately using a scanning electron microscope and a high-resolution transmission electron microscope. Very short silicon nanowires prepared under particular conditions provide direct evidence of the VLS mechanism on a nanometre scale. Our results will be very helpful for the controllable synthesis of Si nanowires.

Template-directed vapor–liquid–solid growth of silicon nanowires

The synthesis of Si nanowires in nanoporous anodic alumina membranes was demonstrated using a combination of Au electrodeposition and vapor–liquid–solid growth at 500 °C using SiH4 as the Si source. The average diameter of the nanowires was 200±54 nm which was close to the pore size distribution of the membranes. High-resolution transmission electron microscopy revealed that the nanowires consist of a crystalline Si core, oriented in the 〈100〉 or 〈211〉 growth direction, with a thin (&amp;lt;3 nm) native oxide coating. In this process, Au terminates both ends of the growing wires, resulting in the formation of Au–Si–Au nanowires.

Are Quasi-One Dimensional Structures of Si Stable?

The stability of quasi-one-dimensional structures of Si is investigated using a generalized tight-binding molecular-dynamics scheme. Our results show that these structures can be stable provided that their geometries consist of a core of fourfold coordinated atoms, surrounded by a threefold coordinated outer surface incorporating one of the most stable reconstructions of bulk Si. Recent experimental works reporting on the synthesis of Si nanowires support these findings.

SiO 2 -enhanced synthesis of Si nanowires by laser ablation

Si nanowires with uniform size have been synthesized by laser ablation of highly pure Si powder targets mixed with SiO2. A bulk quantity of Si nanowires was successfully obtained by mixing 30%–70% of SiO2 into the Si powder target. SiO2 played a crucial role in enhancing the formation and growth of the Si nanowires. The morphology and microstructure of the Si nanowire tips have been systematically characterized by means of high-resolution transmission electron microscopy. No evidence of metal was found at the tips. The results suggest that Si oxide is more important than metal in catalyzing the formation of Si nanowires.