Over 50% of both high school and college students report experience with illicit drugs, and 27% of all Americans abuse drugs at some time in their lives. 1 In fact, 20 million people in the United States reported heavily using and abusing drugs in 1994. 2 Some of these drugs, including cocaine and the amphetamines, are stimulants that increase arousal and provide the user with a psychological “high.” But cocaine, for example, was used by only 3.6% of the U.S. populace in 1994, 3 as compared with the 80% of U.S. adults who drink coffee or tea daily. The average adult in the U.S. and Canada consumes 4 mg/kg/day, 4 and many exceed 15 mg/kg. 5,6 Similarly, Asians and some Europeans consume large amounts of caffeine in tea. Coffee contains a larger amount of caffeine, averaging 85 mg for ground roasted and 60 mg for instant in 5 oz, while leaf tea (5 oz) averages 30 mg and instant tea averages 20. 7

The graphitic nanocarbon allotropes—namely, the fullerenes, graphene, and carbon nanotubes—have attracted significant attention from academia and industry given their useful and controllable optoelectronic properties. Here we provide an up-to-date overview of the growth, alignment, manufacture, and function of engineered carbon nanotube-based electron field emission devices. Recent technological developments in chemical vapor deposition reactor design now allow for the low-cost, en masse production of well-aligned, reproducible carbon nanotubes. For the first time, nanoengineered, functionally enhanced devices can be viably manufactured, whose operation depends critically on both the electronic character and nanotube array geometries. Electron emission is pervasive and central to a wide range of technologies. We conclude by discussing various field emission applications using carbon nanotubes, including parallel electron beam lithography systems, X-ray sources, and displays.

In this chapter, we present a review of our continuing efforts toward the development of discrete, low-dimensional nanostructured carbon-based electron emitters. Carbon nanotubes and nanofibers, herein referred to simply as CNTs, are one-dimensional carbon allotropes formed from cylindrically rolled and nested graphene sheets, have diameters between 1 and 500 nm and lengths of up to several millimeters, and are perfect candidates for field emission (FE) applications. By virtue of their extremely strong sp2 C-C bonding, intrinsic to the graphene hexagonal lattice, CNTs have demonstrated impressive chemical inertness, unprecedented thermal stabilities, significant resistance to electromigration, and exceptionally high axial current carrying capacities, even at elevated temperatures. These near ideal cold cathode electron emitters have incredibly high electric field enhancing aspect ratios combined with virtual point sources of the order of a few nanometers in size. The correct integration and judicious development of suitable FE platforms based on these extraordinary molecules is critical and will ultimately enable enhanced technologies. This chapter will review some of the more recent platforms, devices and structures developed by our group, as well as our contributions towards the development of industry-scalable technologies for ultra-high-resolution electron microscopy, portable x-ray sources, and flexible environmental lighting technologies. © 2012 by Pan Stanford Publishing Pte. Ltd. All rights reserved.

We demonstrate the growth of multi wall and single wall carbon nanotubes (CNT) onto substrates containing commercial 1-μm CMOS integrated circuits. The low substrate temperature growth (450 °C) was achieved by using hot filament (1000 °C) to preheat the source gases (C$_2$H $_2$ and NH$_3$) and in situ mass spe-ctroscopy was used to identify the gas species present. Field effect transistors based on Single Walled Carbon Nanotube (SWNT) grown under such conditions were fabricated and examined. CNT growth was performed directly on the passivation layer of the CMOS integrated circuits. Individual n- and p-type CMOS transistors were compared before and after CNT growth. The transistors survive and operate after the CNT growth process, although small degradations are observed in the output current (for p-transistors) and leakage current (for both p- and n-type transistors).

Angular field emission (FE) properties of vertically aligned carbon nanotube arrays have been measured on samples grown by plasma enhanced chemical vapor deposition and characterized by scanning electron microscope and I-V measurements. These properties determine the angular divergence of electron beams, a crucial parameter in order to obtain high brilliance FE based cathodes. From angular distributions of the electron beam transmitted through extraction grids of different mesh size and by using ray-tracing simulations, the maximum emission angle from carbon nanotube tips has been determined to be about ± 30° around the tube main axis.

A vertically aligned multi-walled carbon nanotube (VACNT) film has been characterized by rectangular waveguide measurements. The complex scattering parameters (S-parameters) are measured by a vector network analyzer at X-band frequencies. The effective complex permittivity and permeability of the VACNT film have been extracted using the Nicolson-Ross-Weir (NWR) approach. The extracted parameters are verified by full wave simulations (CST -Microwave Studio) and very good agreement has been obtained. A systematic error analysis is presented and the errors are within the acceptable range. The performance of VACNT films as an absorber is examined, and comparison with the conventional carbon loaded materials shows that a 90% size reduction is possible whilst maintaining the same absorption level.

A vertically aligned multi-walled carbon nanotube (VACNT) film has been characterized by rectangular waveguide measurements. The complex scattering parameters (S-parameters) are measured by a vector network analyzer at X-band frequencies. The effective complex permittivity and permeability of the VACNT film have been extracted using the Nicolson-Ross-Weir (NWR) approach. The extracted parameters are verified by full wave simulations (CST - Microwave Studio) and very good agreement has been obtained. The performance of VACNT films as an absorber is examined, and comparison with the conventional carbon loaded materials shows that a 90% size reduction is possible whilst maintaining the same absorption level.

In this paper we present our mass participation experiment, Musical Moods. This experiment placed 144 theme tunes online, taken from TV and radio programmes from the last 60 years of the British Broadcasting Corporations (BBC) output. Members of the public were then invited to audition then rate these according to a set of semantic differentials based on the affective categories of evaluation, potency and activity. Participants were also asked to rate their familiarity of the theme tune and how much they liked the theme tune. A final question asked participants to identify the genre of the TV programme with which they associated the tune. The purpose of this is to aid in the affective classification of large-scale TV archives, such as those possessed by the BBC. We find correlations between evaluation and potency, potency and activity but none between activity and evaluation but no clear correlation between affect and genre. This paper presents our key findings from an analysis of the results along with our plans for further analysis. The initial results from this experiment are based on an analyses of over 51,000 answers from over 13,000 participants.

Vertically aligned multiwalled carbon nanotube (VACNT) films have been characterized by rectangular waveguide measurements. The complex scattering parameters (S-parameters) are measured by a vector network analyzer at X-band frequencies. The effective complex permittivity and permeability of the VACNT films have been extracted. The extracted parameters are verified by full wave simulations and very good agreement has been obtained. The results of the systematic error analysis are presented and the errors are within the acceptable range. The performance of VACNT films as an absorber is examined, and comparison with the conventional carbon loaded materials shows that a 90% size reduction is possible while maintaining the same absorption level.

This paper introduces methods used for Music Mood Classification to assist in the automated tagging of television programme theme tunes for the first time. The methods employed use a knowledge driven approach with tailored parameters extractable from the Matlab MIR Toolbox [1]. Four new features were developed, three based on tonality and one on tempo, to enable a degree of quantified tagging, using support vector machines, employing various kernels, optimised along six mood axes. Using a “nearest neighbour” method of optimisation, a success rate in the range of 80-94% was achieved in being able to classify musical audio on a five point mood scale.

In this paper, optical performance of CFEs fabricated from carbon nanotubes and tungsten single crystal is presented. A cold field emitter (CFE) source, which operates at room temperatures or lower, is shown to have better performance over the high temperature Schottky emitter source. Electron emission mainly due to electron tunneling at low temperatures in the cold field emission mode offers a low energy spread and smaller virtual source size. The low energy spread, smaller virtual source size, and higher brightness should result in superior imaging resolution from a CFE compared to the Schottky emitter.

A vertically aligned carbon nanotube mesh emitter array has been fabricated and tested, giving a current density of up to 1.5 A/cm2, and a threshold field of 1.5 V/μm for a current density 1 mA/cm2. Low temperature carbon nanotube growth is used to fabricate the carbon nanotube mesh emitter arrays significantly reducing the cost of the fabrication of large area electron emitters. This system exhibits ultralong lifetime.

A structure composed of zinc oxide nanowires (ZNWs) grown hydrothermally on an array of vertically aligned carbon nanofibers (CNFs) was fabricated and its field emission properties determined and compared with bare CNF arrays. The combination produced a macroscopic turn-on field of 1.2 V/μm which was found to be the lowest reported from ZNWs deposited on a two-dimensional substrate and much less than the equivalent CNFs array (5.2 V/μm). Crucially, field emission was found to be much more stable at higher pressures of 5×10−6 mbar without exhibiting current degradation for a fixed external field, while emitting with a current density of 1 mA/cm2, the current density typically required for backlighting and field emission displays. We propose a self-ballasting mechanism, in which the low carrier density in the zinc oxide prevents current runaway in the presence of adsorbed species.

The aim of this paper is to describe the growth and optimization of ballasted carbon nanotube (CNT) and CNT/Zinc Oxide nanostructures to produce novel electron sources for use in lighting and x-ray applications. © 2010 ITE and SID.

Reconfigurable liquid crystal microlenses employing arrays of multiwalled carbon nanotubes (MWNTs) have been designed and fabricated. The cells consist of arrays of 2 microm high MWNTs grown by plasma-enhanced chemical vapor deposition on silicon with a top electrode of indium tin oxide coated glass positioned 20 microm above the silicon and the gap filled with the nematic liquid crystal BLO48. Simulations have found that, while its nematic liquid crystal aligns with MWNTs within a distance of 10nm, this distance is greatly enhanced by the application of an external electric field. Polarized light experiments show that light is focused with focal lengths ranging from approximately 7 microm to 12 microm.

Transmission terahertz time-domain spectroscopy (THz-TDS) measurements of carbon nanotube arrays are presented. A relatively thin film with vertically aligned multi-walled carbon nanotubes has been prepared and measured using THz-TDS. Experimental results were obtained from 80GHz to 2.5THz, and the sample has been characterized by extracting the relative permittivity of the carbon nanotubes. A combination of the Maxwell-Garnett and Drude models within the frequency range provide a good fit to the measured permittivity.