This PDF file contains the front matter associated with SPIE Proceedings Volume 7761, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

We investigated single wall carbon nanotubes (SWCNTs) synthesized by the HiPCO method and further processed with nitronium hexafluoroantimonate (NO₂SbF₆ : NHFA) treatment using continuous resonant Raman scattering in the range of 570-900 nm. According to the population ratio calculation results from Raman scattering data, it is obvious that semiconducting SWCNTs with small diameter and metallic SWCNTs were selectively removed by NHFA.

Nanostructured carbon nitride films were prepared by pyrolysis assisted chemical vapour deposition(CVD). A two zone furnace with a temperature profile having a uniform temperature over a length of 20 cm length has been designed and developed. The precursor Azabenzimidazole was taken in a quartz tube and evaporated at 400 ⁰C. The dense vapours enter the pyrolysis zone kept at a desired temperature and deposit on the quartz substrates. The FTIR spectrum of the prepared samples shows peaks at 1272 cm^-1 (C.N stretching) and 1600 cm^-1 (C=N) confirms the bonding of nitrogen with carbon. Raman D and G peaks, are observed at 1360 cm^-1 and 1576 cm^-1 respectively. XPS core level spectra of C 1s and N 1s show the formation of π bonding between carbon and nitrogen atoms. The size of the nano crystals estimated from the SEM images and XRD is ~100 nm. In some regions of the sample a maximum of 57 atom % of nitrogen has been observed.

In this paper we demonstrate the efficiency of porous anodic alumina (PAA) to confine the growth of silicon nanowires (SiNWs). High-density arrays of parallel, straight and organized SiNWs have been realized, by Hot Wire Chemical Vapor Deposition (HW-CVD) growth process inside PAA templates with electrodeposited copper as catalyst. The PAA was made by the anodization of an aluminium layer, followed by the catalysts electrodeposition at the bottom of the pores. Subsequently, SiNWs were grown in a modified HW-CVD reactor with SiH₄ as the precursor gas. The morphology and the structure of the wires have been investigated by SEM and TEM, and their collective electrical behavior has been characterized with a 2-probes device.

We present our work on the growth and functionalization of carbon nanotubes (CNTs). A significant challenge in the growth of aligned single, double and triple walled nanotubes is in the deposition of a controlled thickness catalyst layer. Conventional techniques using line of sight deposition such as sputtering and evaporation produce uniform catalyst layers only when extreme care is taken in the placement of flat substrates. Growth of aligned low wall number carbon nanotubes on contoured, complex geometry, or large surface area substrates is simply not technically feasible through these techniques. Using iron atomic layer deposition (ALD) with ferrocene and oxygen precursors for catalyst deposition circumvents the line of sight problems and allows for uniform coverage across almost all substrates. Furthermore the ALD technique allows for extremely accurate and reproducible thickness depositions. Using these ALD catalyst layers reproducible aligned arrays consisting of primarily double and triple wall CNTS can be fabricated. Conformal coatings onto high aspect ratio surfaces are particularly challenging. The walls of single carbon nanotubes in a nanotube array are inaccessible by line of sight techniques. ALD circumvents this problem by relying on a gas-surface reaction to initiate growth. Generally, growth of ALD films on CNTs results in beading of the deposited materials around CNT defects. This is particularly true of high surface energy materials. The number of nucleation sites and the onset of growth of Pt by ALD can be tuned by use of Ar plasma, O2 plasma and chemical functionalization.

We successfully synthesized organized Carbon nanotubes (CNTs) and Silicon Nanowires (SiNWs) arrays using LPAA. This approach can yield very dense assemblies of nano-objects with a planar-type organization compatible with existing tools inherited from advanced microelectronic processes and adapted to electronic devices as field effect transistors, interconnects, sensors, etc. CNTs/SiNWs were grown using Hot-filament Chemical Vapor Deposition (HFCVD) within lateral-type porous anodic alumina. We demonstrate that the pulsed electrodeposition of metal nanoparticles to be further used as catalysts inside the membranes requires specific thinning and pore widening process to remove the alumina barrier layer located at the bottom of the pores. The growth of CNTs was found to strongly depend on the electrodeposition conditions as well as on the CVD parameters. In addition, we found that introducing atomic hydrogen (generated using a hot-wire) as etching agent was essential to prevent parasitic carbon/silicon deposition on the surface of PAA or on the wall of pores and to improve CNTs/NWs growth. Such organized CNTs/SiNWs arrays are very promising as advanced microelectronic devices and their potentiality for photosensing applications were investigated.

In this study, we present electric field (E-field) modelling and experiment of arrays of vertically grown carbon nanotubes as three dimensional electrode structures, in order to address liquid crystal molecules in a switchable nano-photonic device. The electric field spawned by the nanotube electrodes is used to align the liquid crystal molecules to generate a gradient refractive index profile across the device. It was observed that multiple nanotube groups generated wide and symmetrical electric fields compared to other geometries. We have utilized nano-photonic devices based on the simulation results and compared them with experimentally obtained electro-optic characteristics. These devices have many applications in voltage reconfigurable micro-optical systems.

Carbon nanotubes (CNTs) have been attracting strong attention owning to their fascinating one-dimensional structure and unique mechanical, electrical and thermal properties. CNTs are promising in various important applications, but their application is severely impeded by their poor processibility, since they do not melt and usually have quite low solubility in solvents. The methods reported in literature for the dispersion of CNTs require an ultrasonication of CNTs under a high power or a chemical reaction, which can alter the physical properties and bring severe defects to CNTs. They are still far away from processing of CNTs in large scale, because only in a small amount of CNTs can be dispersed by these methods. Here, we will report a simple and efficient method to directly disperse CNTs in nonionic surfactants. CNTs and a nonionic surfactant form gels by mechanical grinding. The gels can be processed into CNT films by coating. The CNT films have good adhesion to the substrates and do not detach from the substrate after several weeks. We also demonstrate that the CNT films prepared by our method can be used as the counter electrode of highperformance dye-sensitized solar cells (DSCs). The photovoltaic efficiency is comparable to the devices using conventional noble platinum as the counter electrode.

Observations of the Earth are extremely challenging; its large angular extent floods scientific instruments with high flux within and adjacent to the desired field of view. This bright light diffracts from instrument structures, rattles around and invariably contaminates measurements. Astrophysical observations also are impacted by stray light that obscures very dim objects and degrades signal to noise in spectroscopic measurements. Stray light is controlled by utilizing low reflectance structural surface treatments and by using baffles and stops to limit this background noise. In 2007 GSFC researchers discovered that Multiwalled Carbon Nanotubes (MWCNTs) are exceptionally good absorbers, with potential to provide order-of-magnitude improvement over current surface treatments and a resulting factor of 10,000 reduction in stray light when applied to an entire optical train. Development of this technology will provide numerous benefits including: a.) simplification of instrument stray light controls to achieve equivalent performance, b.) increasing observational efficiencies by recovering currently unusable scenes in high contrast regions, and c.) enabling low-noise observations that are beyond current capabilities. Our objective was to develop and apply MWCNTs to instrument components to realize these benefits. We have addressed the technical challenges to advance the technology by tuning the MWCNT geometry using a variety of methods to provide a factor of 10 improvement over current surface treatments used in space flight hardware. Techniques are being developed to apply the optimized geometry to typical instrument components such as spiders, baffles and tubes. Application of the nanostructures to alternate materials (or by contact transfer) is also being investigated. In addition, candidate geometries have been tested and optimized for robustness to survive integration, testing, launch and operations associated with space flight hardware. The benefits of this technology extend to space science where observations of extremely dim objects require suppression of stray light.

Epitaxial graphene (EG) grown on the carbon-face of SiC has been shown to exhibit higher carrier mobilities in comparison graphene grown via most other methods, while also remaining amenable to wafer-scale growth and fabrication. The ability to transfer large area (>mm²), continuous graphene films to arbitrary substrates while maintaining the electrical and structural integrity of the film is desirable. We demonstrate the dry transfer of EG from the C-face of 4H-SiC onto SiO₂, GaN and Al₂O₃ substrates using thermal release tape both with and without a PMMA backing layer. Van der Pauw devices fabricated from C-face EG that were transferred to SiO₂ and sapphire exhibited similar Hall effect mobilities, with an approximate three-fold reduction in carrier density when compared to devices fabricated on as-grown material. Raman spectroscopy illustrated that the optimized transfer process did not adversely affect the material quality, while XPS was used to both determine the transfer efficiency as well as to observe the presence of atomic silicon within the as-grown EG films. This latter observation may provide insight into the identity of the native dopant within these materials and/or a point defect that could be limiting carrier mobility.

Graphene has been given great attention to overcome current physical limits in electronic devices and its synthesis routes are developing rapidly. However, graphene film manufacturing is still hindered by either low throughput or low material quality. Here, we present a low temperature PE-CVD assisted graphene growth process on nickel thin films deposited on silicon oxide. Furthermore, our process leads to the formation of two separated graphene films, one at the nickel surface and the other at the Ni/SiO2 interface. A mixture of methane and hydrogen was employed as carbon precursor and activated by DC plasma. We found that the number of graphene layers on top of nickel can be controlled by carbon exposure time, from 1 to around 10 layers. Further annealing process of samples allowed us to achieve improved graphene films by the dissolution and segregation-crystallization process.

Bending tests of carbon nanotube thin-film transistors on flexible substrate have been characterized in this paper. The device channel consisting of dense, aligned, 99% pure semiconducting single-walled carbon nanotubes (SWCNT) are deposited using dip-coat technique on sacrificial substrate and then transferred on to the device substrate. Ink-jet printing technique is used to form the source, drain and gate electrodes using silver ink. A novel source-drain contact formation using wet droplet of silver ink prior to CNT thin-film application has been developed to enhance source-drain contact with the CNT channel. Bending test data on CNT-TFT test structures show minimal change (less than 10%) in their performance. To reduce the device performance variation due to bending, flexible electronic circuit is designed such that vertical device orientation is used for backward bending and horizontal orientation is used for forward bending.

Exploring renewable, sustainable and green energy resources is a critical challenge for scientists and engineers. Large-scale ambient energy, such as the solar energy is available but current technologies are not yet ready to capture it with great efficiency. The sun radiates visible light and also infrared energy, some of which is soaked up by the earth and later released as radiation for hours after sunset. In this study, the use of arrays of carbon nanotubes (CNT) Field Effect Transistors (FET) as photovoltaic (PV) elements is investigated. The interaction between electromagnetic waves and the CNT array is simulated using COMSOL Multiphysics in order to calculate the amount of absorbed power. The effects of the distribution of PV elements on the array performance are studied in order to maximize power absorption for the same number of elements.

It is shown that it is possible to obtain the phonon frequency distribution function (FDF) of aligned multi-walled carbon nanotubes (MWNT) by unfolding its temperature variation of specific heat in the temperature range 1.8-250 K. An anisotropic dynamical model which takes into account the presence of two-dimensional modes on the surface of the tube and the intertube coupling has been used as a trial function to carry out the unfolding process numerically. The aligned MWNT sample turns out to be somewhat similar to graphite.

This paper presents graphene nanoribbon (GNR) Schottky diode through an analytical approach. To achieve an analytical relation for channel current, first an analytical equation for potential distribution within the GNR is offered. Then by using the WKB approximation, transmission probability through Schottky barriers is derived. Finally the channel current is analytically achieved, which is a function of physical and electrical parameters including gate insulator thickness, Schottky barrier height, drain bias voltage, gate bias voltage, GNR width, and subband number. To get a rectification behavior of presented device, two different metals have been considered at the two ends of a p-type semiconducting GNR resulting in asymmetric contacts. The effect of different parameters such as gate bias voltage, GNR width, and contact metals on the rectification behavior is investigated. We demonstrate that the rectification characteristic, threshold voltage, reverse saturation current, and reverse turn-on voltage can be tuned through the use of these parameters. The derived analytical current well describes the rectifying behavior of presented GNR Schottky diode.