Silicon Carbide Nanorods Research Articles

Single crystalline silicon carbide nanorods synthesized by hydrothermal method

A new and simple hydrothermal process has been used to synthesize single crystalline silicon carbide nanorods. The synthesized silicon carbide nanorods have a length of about 1 μm and nearly same diameter of about 40 nm. We have observed that the nanorods possess a well-defined single crystalline structure with a thin layer of amorphous silica on the surface. The X-ray diffraction analysis demonstrates that the structure of silicon carbide nanorods is β-SiC. Raman shifts of the silicon carbide nanorods are discussed and the oxide-assisted growth mechanism is proposed to explain the formation and growth of silicon carbide nanorods.

Fabrication of quasi-one dimension silicon carbide nanorods prepared by RF sputtering

Anodic aluminum oxide (AAO) template was prepared by a two-step anodization method at low temperature (1 °C) and silicon carbide was deposited on the templates by non-reactive radio frequency sputtering method. Well-aligned quasi-one dimension silicon carbide nanorods with the average diameter about 80–90 nm and a mean length of 400 nm were obtained perpendicular to the substrate and observed by AFM and SEM after the aluminum substrates were striped off. Then some samples were annealing at flowing N 2 at 400, 500 and 600 °C and FTIR was performed on these samples to obtain the information of structure.

Modification of SiC based nanorods via a hydrogenated annealing process

We present a novel and simple method to modify silicon carbide nanorods coated in quartz by annealing in an ammonia atmosphere. The process allows the coaxial nanorod to be restructured such that the core becomes quartz with a thick silicon carbide sheath. The nanorods were analysed using bulk sensitive EELS and Raman spectroscopy and on a local scale using TEM imaging and spectroscopy.

Synthesis of One-Dimensional Nanostructured Silicon Carbide by Chemical Vapor Deposition

Nanorods of the wide-bandgap semiconductor silicon carbide belong to a promising group of one-dimensional materials with potential applications extending from reinforcement of composites to applications as building blocks that can be logically assembled into appropriate two- (and three-) dimensional architectures, permitting researchers to exploit their unusual electronic, optical, and other properties. Specific to the most common silicon carbide polytypes are a low intrinsic carrier concentration, an exceptionally high breakdown electric field, high thermal conductivity, high-temperature stability, and resistance to an aggressive environment. This should permit one to develop even submicron-level SiC-based devices operating under high-temperature, high-power, and/or high-radiation conditions, under which conventional semiconductors cannot function. Detailed control of the conditions favorable for the nucleation and growth processes of nanorods of a given SiC polytype is necessary because the electrical and optical properties of each SiC polytype are very different. Therefore, a systematic investigation of factors that primarily influence the morphology and polytype of a vapor-phase-grown SiC has been made in the present work. These factors were the temperature, the flow rates of the gaseous precursors, and the Si/C molar ratio in the gas phase. In order to investigate the role of these factors, the “cold gas-hot substrate” chemical vapor deposition (CVD) method has been applied, because it permits them to be closely controlled in a wide range. While in the overwhelming majority of previous investigations nanorods of the 3C SiC polytype have been grown, the present work delineates conditions that are favorable for the growth of single-phase 2H, 3C, 15R, and 6H SiC nanorods, respectively.

Formation of Silicon Carbide Nanorods from Wood‐Based Carbons

Man‐made ceramic wood similar to petrified wood found in nature can be used at high temperature as the high oxidation rate of carbon above 500°C is suppressed by a 1 µm thin SiC coating similar to the shuttle's heat shield. Possible applications are in the field of energy production, e.g., gas filters. In this paper, Japanese cedar was carbonized at 700°C, vacuum infiltrated with tetraethylorthosilicate (TEOS), and heated at 1,500°C for 30 min using a pulse current heating device. A FIB–SEM dual beam microscope combination was used to investigate the SiC/C composite micro‐texture. By milling away successive slices of material approximately 20 nm in thickness, it was possible to confirm that a reaction layer of SiC, about 60 nm in thickness, covers uniformly the surface of all cell walls. Furthermore, SiC nanorods were observed, growing more or less randomly in the charcoal pores. Cross‐sectional SEM images of the SiC nanorods showed that either hollow or solid structures could be formed, having diameters ranging from 100 to 500 nm. The SiC nanorod formation is being initiated by a catalytically operating SiC particle in the SiC coating. TEM analysis confirmed that they were grown along the [1 1 1] direction and indicated that an additional carbon layer covers the external surface of the rods making the rods more resistant against electron beam damage.

Silicon Carbide Nanorods and Ceramics from Wood

Japanese cedar carbonized at 700degreesC was vacuum infiltrated with tetraethylorthosilicate (TEOS), and heated for 30 min at 1400, 1600 and 1800degreesC by electric pulse heating. The microstructure was investigated by X-ray diffraction and electron microscopy. Extra peaks in the XRD scans could be traced back to beta-SiC. Preliminary Auger analysis indicated an increase of the Si signal in pore walls. This was considered together with SEM images in agreement with the concept of a reaction layer covering the pore walls. Moreover, a large number of nanorods were present inside the pores. TEM analysis confirmed them to be SiC nanorods grown along the direction.

Synthesis of silicon carbide nanorods by catalyst-assisted pyrolysis of polymeric precursor

In this Letter, we report the synthesis of β-SiC nanorods by the pyrolysis of a polysilazane polymeric precursor in the presence of 3 wt% FeCl 2 as a catalyst. The precursor is completely converted to the nanorods after heat-treated at 1700 °C for 2 h, accompanied by ∼50% weight loss. Electron microscopy study reveals that the nanorods preferentially grow along [1 1 1] direction; and the diameters of the nanorods range from 80 to 200 nm and lengths are ∼4 μm. A solid–liquid–solid growth mechanism is proposed.

Controlled growth of silicon carbide nanorods by rapid thermal process and their field emission properties

Silicon carbide nanorods with a typical diameter of about 20 nm and a length ranging from 100 nm to a few microns have been formed by rapid thermal processing (RTP) of thin films containing a mixture of carbon and iron over silicon wafers at temperatures ranging from 1000 to 1200 °C. It is proposed that SiC nanorods were formed by solid–liquid–solid process of Si and C with Fe as catalyst. The controllability offered by RTP is crucial as field emission study showed that the turn-on field of the SiC nanorods was a strong function of their length and number density.

Structural transformation of carbon nanotubes to silicon carbide nanorods or microcrystals by the reaction with different silicon sources in rf induced CVD reactor

Silicon carbide (SiC) nanorods and microcrystals were synthesized through a two-step reaction scheme. Carbon nanotubes (CNTs) were first grown over metal catalyst-loaded Si(1 0 0) wafer surface by thermal decomposition of C 2H 2. The grown CNTs were then reacted with a gas mixture of SiH 4 and C 3H 8 or tetramethylsilane (TMS) to form β-SiC nanostructures. The growth of SiC nanorods was observed when CNTs were reacted with SiH 4 and C 3H 8, whereas SiC microcrystals were formed when reacting the CNTs with TMS. However, the SiC nanostructures were not grown without CNTs. The diameter of the nanorods was around six times larger than that of the mother nanotubes. The nanorods were crystalline β-SiC with the diameter of 300–400 nm and grew along (1 1 1) direction. The structural transformation of CNTs to SiC nanorods or to microcrystals during the reaction was discussed in this paper.

Effect of chemical vapor deposition energy sources on the structure of SiC prepared by carbon nanotubes-confined reaction

Silicon carbide (SiC) nanorods and microcrystals were synthesized with controlled structure through a two-step reaction scheme. Carbon nanotubes (CNTs) were first grown by the thermal decomposition of C2H2 over a Fe/Co metal catalyst loaded on a Si(100) wafer surface. The grown CNTs were then reacted with tetramethylsilane (TMS) to form β-SiC nanorods or microcrystals. SiC nanorods were observed when CNTs reacted with TMS at 1100 °C in an IR-induced heating chemical vapor deposition (CVD) reactor, whereas SiC microcrystals were formed at 1250 °C in an rf-induced-heating CVD reactor. Higher temperature and longer time were favorable for the growth of good quality SiC crystals. The blueshift of the PL spectra was observed from the SiC nanorods and SiC microcrystals. The structural change of CNTs in the growth was discussed in this work.

Nanomaterials for field electron emission: preparation, characterization and application

We review the current development in synthesis and deposition techniques of quasi-one-dimensional nanomaterials and recent achievements in the study of the field electron emission properties of these materials. Major findings are given from our recent experimental study of the field electron emission characteristics of carbon nanotubes, copper sulfide and silicon carbide nanorods. The study reveals that the above nanomaterials are promising candidates as cold cathode electron emitters. Furthermore, we review the recent development of techniques for growing and depositing the above nanomaterials in device structures. Typical device structures and their performance are also shown.

Simultaneous growth of silicon carbide nanorods and carbon nanotubes by chemical vapor deposition

Silicon carbide nanorods and carbon nanotubes are grown simultaneously on Ni-coated Si(001) substrates by chemical vapor deposition. The nanorods have a non-uniform diameter (average ≈100 nm) significantly larger than that of the nanotubes (<30 nm). Tips of the nanorods are decorated with catalyst particles. Both these features indicate that the SiC nanorods are not obtained through the chemical conversion of nanotubes. We demonstrate that the relative amounts of nanorods and nanotubes can be controlled by adjusting the Ni film thickness. Variants of our approach are potentially useful for creating hybrid architectures of high-aspect ratio nanostructures in one growth step.

Growth and emission properties of β-SiC nanorods

A one step procedure has been developed to grow beta-silicon carbide (β-SiC) nanorods from a solid carbon and silicon source on silicon substrates using a hot filament chemical vapor deposition. The growth process was catalyzed by the impurities of metallic particles confined in the solid source plate made of a mixture of graphite and silicon powders pressed at 150°C. Hydrogen was introduced into a reaction chamber to react with the solid source. The resulting process produced, hydrocarbon and hydrosilicon radicals, which subsequently reacted on the Si substrate surface and presumably formed SiC nanorods. The nanorods consisted of a crystalline β-SiC core with an amorphous silicon oxide shell layer. The nanorods were 10–30 nm in diameter and less than 1 μm in length. Field emission characteristics of the β-SiC nanorods were investigated using current-voltage measurements and the Fowler–Nordheim equation. The silicon carbide nanorods exhibited high electron field emission with high stability. Along with the ease of preparation, these silicon carbide nanorods are believed to have potential application in electron field emitting devices.

Nanobeam Mechanics: Elasticity, Strength, and Toughness of Nanorods and Nanotubes

The Young's modulus, strength, and toughness of nanostructures are important to proposed applications ranging from nanocomposites to probe microscopy, yet there is little direct knowledge of these key mechanical properties. Atomic force microscopy was used to determine the mechanical properties of individual, structurally isolated silicon carbide (SiC) nanorods (NRs) and multiwall carbon nanotubes (MWNTs) that were pinned at one end to molybdenum disulfide surfaces. The bending force was measured versus displacement along the unpinned lengths. The MWNTs were about two times as stiff as the SiC NRs. Continued bending of the SiC NRs ultimately led to fracture, whereas the MWNTs exhibited an interesting elastic buckling process. The strengths of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical values. Because of buckling, the ultimate strengths of the stiffer MWNTs were less than those of the SiC NRs, although the MWNTs represent a uniquely tough, energy-absorbing material.

Continuous synthesis and characterization of silicon carbide nanorods

A two-step reaction scheme has been employed for the synthesis of SiC nanorods at 1400°C. SiO vapour was generated via the silicon reduction of silica, and then this SiO vapor reacted with carbon nanotubes to form SiC nanorods. The morphology and structure of the nanorods were characterized by XRD, TEM, IR and Raman spectroscopy. The nanorods are single crystalline β-SiC with the diameters ranging from 3 to 40 nm. A broad photoluminescence peak located around 430 nm under 260 nm UV fluorescent light excitation at room temperature is observed. A growth model of SiC nanorods is proposed.