https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf

Advances in the science and technology of carbon nanotubes and their composites: a review

The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotube devices integrated into silicon technology.

https://science.sciencemag.org/content/sci/283/5401/512.full.pdf

Self-Oriented Regular Arrays of Carbon Nanotubes and Their Field Emission Properties

Nanotubes from Carbon.

Ordered carbon molecular sieves exhibiting Bragg diffraction of X-ray lines have been synthesized for the first time, using mesoporous silica molecular sieves as the template. Sucrose was converted to carbon inside the mesopores of the silica molecular sieves through a mild carbonization process using a sulfuric acid catalyst. The carbon molecular sieves were obtained after the removal of the silica framework using an aqueous solution of sodium hydroxide. The X-ray diffraction, transmission electron microscopy, and pore size analysis showed that the structure of the carbon molecular sieves consisted of a three-dimensional regular array of uniform mesopores 3 nm in diameter. The structure was not simply a negative replica of the used silica template, but the synthesis mechanism involved the unique transformation into a new ordered array that was triggered by the removal of the silica frameworks. The highly ordered mesoporous texture suggested its scientific and technological importance as a new shape-selec...

Synthesis of highly ordered carbon molecular sieves via template-mediated structural transformation

Polymer/carbon nanotube (CNT) composites are expected to have good processability characteristics of the polymer and excellent functional properties of the CNTs. The critical challenge, however, is how to enhance dispersion and alignment of CNTs in the matrix. Here, we review recent progress and advances that have been made on: (a) dispersion of CNTs in a polymer matrix, including optimum blending, in situ polymerization and chemical functionalization; and (b) alignment of CNTs in the matrix enhanced by ex situ techniques, force and magnetic fields, electrospinning and liquid crystalline phase-induced methods. In addition, discussions on mechanical, thermal, electrical, electrochemical, optical and super-hydrophobic properties; and applications of polymer/CNT composites are included. Enhanced dispersion and alignment of CNTs in the polymer matrix will promote and extend the applications and developments of polymer/CNT nanocomposites.

Dispersion and alignment of carbon nanotubes in polymer matrix: A review

Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.

https://science.sciencemag.org/content/sci/274/5293/1701.full.pdf

Large-Scale Synthesis of Aligned Carbon Nanotubes

Both optical transmission spectroscopy and photothermal deflection spectroscopy are used to determine the spectra of C70 thin films over a wide energy range (0.6–6.5 eV). Based on a molecular orbital model, the optical transitions for the C70 thin film are analyzed. The weak absorption spectra of C70 thin films are similar to that of an amorphous semiconductor. The optical energy gap is derived by a Tauc plot as 1.66 eV. The gap region can be described in terms used for amorphous semiconductors, having features such as an Urbach edge and subgap defect absorption, which are interpreted as a broadening due to disorder or impurities. The effects of the deflection medium on the weak absorption spectra of C70 films are discussed.

/pdf/optical-absorption-spectra-of-c70-thin-films-1kzcng9196.pdf

Optical absorption spectra of C70 thin films

The growth of carbon nanotubes from catalytic thermal decomposition of acetylene on fine iron particles has been studied. Electron microscopic images of the carbon nanotubes “as formed” and after annealing treatment are presented. Besides the ordinary carbon nanotubes which have been reported (S. Iijima, Nature, 354 (1991) 56), we have found, at first time, two other new kinds of carbon nanotubes: one is straight or curved nanotube with many irregular multi-layered diaphragms in the hollow core, in particular, the fringes of the wall of the tubes are not parallel to the axis of the tube; another one has many regular diaphragms (bamboo-like) which keep almost constant distance with each other. A model that postulates two steps growth of nanotubes from catalyst particles is proposed to explain the microstructure of the novel carbon nanotubes.

A structure model and growth mechanism for novel carbon nanotubes

The elastic free energy of carbon nanotubes grown by iron-catalyzed decomposition of acetylene is introduced to describe the possible tubular shapes. The equilibrium shape equation can be obtained by the first variation of the elastic free energy of the slightly distorted tube. The model is consistent with both stable and metastable shapes observed in our experiments. The results are due to the fluctuation of growth conditions, such as the pressure, temperature, and composition of the vapor. \textcopyright{} 1996 The American Physical Society.

Equilibrium shape equation and possible shapes of carbon nanotubes.

Inline voltage ramp stress (VRS) is used for fast wafer level reliability (fWLR) monitoring. For hot carrier injection (HCI) degradation, saturation current is monitored as drain and gate voltages are gradually increased. NFET VRS HCI is consistent with constant voltage stress (CVS) model, while PFET CVS model and VRS slope exhibits a large discrepancy. Similar to CVS data at short stress times and low gate voltage (Vg), the discrepancy is due to electron trapping during VRS when gate bias is less than drain voltage (Vd). As the gate voltage increases, the charge-trapping component reduces giving a better correlation for VRS slope versus the CVS model.

Ri‐an Zhao

Papers

Large-Scale Synthesis of Aligned Carbon Nanotubes

Optical absorption spectra of C70 thin films

A structure model and growth mechanism for novel carbon nanotubes

Equilibrium shape equation and possible shapes of carbon nanotubes.

Voltage Ramp Stress Test Optimization for Wafer Level Hot Carrier Monitoring in FinFET