Selective Hemispherical Grained Polysilicon Transformation for 256 MB, 1 GB Dynamic Random Access Memory and Beyond

Research into Carbon Nanotubes and their applications is fast becoming an extremely popular topic, and any means to greatly improve the synthesis process has a huge marketability. While investigating the feasibility of continuous production of single-walled carbon nanotubes in a vertical Swirled Fluid Chemical Vapour Deposition (CVD) reactor, it was discovered that helical nanotubes were lifted from the reactor by the gas current while straight tubes remained behind. Investigation into the merits provided by the helical structure illustrated the greatly increased likeliness for helical tubes to be lifted from the reactor by the carrier gas giving rise to positive speculation of their possible use in vertical CVD reactors in the future.

The continuous search for effective and efficient engineered materials towards solving human challenges is in continuous needs. This study reports the preparation of alumina from kaolin as catalyst support using methanol as precipitant for the synthesis of multiwalled carbon nanotubes (MWCNTs) in a horizontal chemical vapour deposition (CVD) reactor. The process involved thermal treatment of kaolin in a static air furnace, leaching of the treated kaolin in tetraoxosulphate(VI) acid , precipitation in methanol medium, washing in distilled water and calcination at . The alumina in the kaolin was successfully leached and a cubic structure alumina of high thermal stability was synthesized. The alumina was then characterised and utilised as support for the bimetallic catalyst (Fe-Ni) using wet impregnation method. The produced catalyst was used to produce CNTs in a CVD reactor. The thermal properties, surface morphologies, surface functional groups, crystallinity, elemental analyses, and surface areas of the starting kaolin, alumina, prepared bimetallic catalyst (Fe-Ni/alumina) and the synthesized MWCNTs were determined using TGA/DTA, HRSEM, FTIR, XRD, EDX, and BET respectively. The XRD analysis of the bimetallic catalyst was employed to determine its average crystalline particle size to be 26.23 nm using Scherer equation. Tip growth mechanism of MWCNTs was observed during the MWCNTs nucleation process with 41.2 nm external diameters, length and 340 aspect ratio using dynamic light scattering (DLS) technique. The purified MWCNTs showed high antibacterial activities at long exposure time. The results of the various analysis conducted show that the synthesized alumina has potential properties as catalyst support for MWCNTs growth via CVD technique.

A self‐consistent set of thermochemical data for 88 chemical species in the B/F/H/N system is obtained from ab initio electronic structure calculation. Calculations were performed for both stable and radical species. The quantities calculated include the atomization energy (∑ D0), heat of formation (ΔHf) at 0 K and 298.15 K, and bond dissociation energies (BDE) for all species. Good agreement is found between the calculation data and experimental or theoretical reference data for the quantities analyzed in this work for several species containing B, F, H, and N atoms. We also present a compilation of experimental and theoretical atomization energies (16 experimental × 26 theoretical data), heat of formation at 0 K (25 experimental × 26 theoretical data), heat of formation at 298 K (29 experimental × 36 theoretical data), and bond dissociation energy for several species. Polynomial fits of the predicted thermodynamic data (heat capacity, entropy, and enthalpy) over the 200–6000 K temperature range are also included, for the 88 species. The species analyzed in this study are important in a kinetic mechanism for growth boron nitride films in a Chemical Vapour Deposition (CVD) reactor. It is generally difficult to optimize conditions in a CVD reactor because films properties depend on complex interactions involving heat and mass transport, chemical kinetics, and thermochemistry. Developing a reliable set of thermodynamic data is a necessary first step for system optimization, since it provides important constraints on the possible reaction mechanism. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005

In this paper, a laboratory chemical vapor deposition (CVD) reactor is described, which features an opposing screw rotating fluidized bed. The reactor efficiently concentrates powdered reactants in the reaction zone while maintaining fluidization independent of powder properties. This allows for lab-scale CVD processing of many small powder samples at high yields and without the need for re-adjustment of fluidization parameters for different samples. Alumina and graphite were carbon-coated and characterized in lithium batteries. The deposited carbon layer had a density of 1.84 g/ml and a capacity of 225 mA h/g when cycled between 7 mV and 0.9 V in lithium cells. Carbon coatings applied by this CVD reactor onto graphite particles were found to be effective at reducing surface reactions during cycling in lithium cells. We suggest that utilization of this opposing screw rotating fluidized bed reactor can effectively apply CVD coatings to small laboratory powder samples, with particular utility for Li-ion battery materials.

Modelling of Cu thin film growth by MOCVD process in a vertical reactor

A model is presented to simulate the non-Boussinesq flow in a vertical, two-dimensional, chemical vapor deposition (CVD) reactor under atmospheric pressure. Temperature-dependent conductivity, mass diffusivity, viscosity models, and reactive species mass transfer to the substrate are incorporated. In the limits of small Mach number and small aspect ratio, asymptotic expressions for the flow, temperature, and species fields are developed. The interaction of inertial and buoyancy-driven flows in a ramped temperature environment is described. The increase of heat at the reactor entrance leads to a recirculation of the flow at the entrance due to volumetric expansion of the gas. The recirculating flow forces the fresh incoming stream of gas toward the substrate. This, in turn, effects the species deposition rate. Soret diffusion effects are also investigated. Analytical solutions predict an inverse relationship between temperature field and concentration field due to Soret effects. This finding is consistent ...

A numerical verification procedure and the effects of operating conditions in a large, vertical, and close-spaced reactor for metalorganic chemical vapor deposition are investigated through simulation and analysis. A set of epitaxy experiments are presented for verifying the growth rate of the gallium nitride (GaN) mechanism reported in our previous study. The full governing equations for continuity, momentum, energy, and chemical reaction are solved numerically. The results show that the real operating parameters (susceptor temperature: 1188 °C or 1238 °C; pressure: 100–300 torr) affect thin-film uniformity, and the predicted growth rates agree reasonably well with the experimental data, indicating the accuracy of the projected chemical reaction mechanisms.

Balancing reactor fluid dynamics and deposition kinetics to achieve compositional variation in combinatorial chemical vapor depositions

Defect passivation by hydrogen reincorporation for silicon quantum dots in SiC/SiOx hetero-superlattice

Epitaxial BaTiO3 thin films were deposited on MgO (100) in a rotating disk vertical metalorganic chemical vapor deposition (MOCVD) reactor at 700°C. The metalorganic sources used were titanium tetraisopropoxide and the highly volatile fluorinated barium precursor (Ba(hfa)2∙pentaethyleneglycolethylbutylether(PEB)). To facilitate growth at the lower temperature while suppressing the formation of BaF2 impurity phases, a strong oxidant consisting of a mixture of 80% N2O and 20% O2 was employed. The BaTiO3 films deposited at 700°C are phase pure and show only BaTiO3 {001} x-ray diffraction peaks. The x-ray rocking curve full width at half maximum (FWHM) of the BaTiO3 (002) peak was 0.82°. The fourfold symmetry and coincident position of the {110} peaks for both the film and substrate confirms in-plane epitaxy of cube-on-cube orientation. The Φ-scan FWHM of the BaTiO3 film is 1.05°. The growth temperature in this work is lower than the temperatures used in most comparable thermal MOCVD epitaxial oxide processes for BaTiO3.

LPCVD deposition of silicon nitride assisted by high density plasmas

The fundamental mechanisms of diamond growth occur on the atomic scale; however, the geometry of the deposition reactor and the other operating parameters directly affect the chemical composition of the gas and the temperature at the growth surface. The properties are, in turn, controlled by both atomic- and microstructural-scale features. By developing diamond-growth models at each length scale and coupling the output of one model into the next, a comprehensive simulation scheme for diamond deposition is realized. This approach provides the missing link between chemical vapor deposition reactor design/operating conditions and the material structure/properties.

Computation of three-dimensional flow and thermal fields in a model horizontal chemical vapor deposition reactor

A dome-shaped cavity type microwave plasma chemical vapor deposition reactor for diamond films deposition

Influence of the synthesis conditions of silicon nanodots in an industrial low pressure chemical vapor deposition reactor