Sarah Lastella

Density control of single-walled carbon nanotubes using patterned iron nanoparticle catalysts derived from phase-separated thin films of a polyferrocene block copolymer

Single-walled carbon nanotube (SWNT) density and bundle size has been controlled by a simple one step CVD growth process using a polyferrocenylsilane block copolymer as the pre-organized catalyst source.

Parallel arrays of individually addressable single-walled carbon nanotube field-effect transistors

High-throughput field-effect transistors (FETs) containing over 300 disentangled, high-purity chemical-vapor-deposition-grown single-walled carbon nanotube (SWNT) channels have been fabricated in a three-step process that creates more than 160 individually addressable devices on a single silicon chip. This scheme gives a 96% device yield with output currents averaging 5.4mA and reaching up to 17mA at a 300mV bias. Entirely semiconducting FETs are easily realized by a high current selective destruction of metallic tubes. The excellent dispersity and nearly-defect-free quality of the SWNT channels make these devices also useful for nanoscale chemical and biological sensor applications.

Reversible separation of single-walled carbon nanotubes in bundles

We show that electrostatic charging of nanotubes and the consequent repulsion can lead to reversible separation of individual single-walled carbon nanotubes in bundles. Low-energy electron beam irradiation leads to this completely reversible phenomenon. A simple semianalytical model is used to explain the observed separation mechanism. The reversibility of the separation process is attributed to discharging and thermal-fluctuation induced motion of the nanotubes in ambient air. Further, the separation impacts the electrical conductance of small nanotube bundled devices.

Single Walled Carbon Nanotube Junctions for Nano-Electronics and Sensors

Using a Fe-containing diblock copolymer as the catalyst, single walled carbon nanotubes (SWNTs) have been grown on Si/SiO2 substrate by chemical vapor deposition (CVD) technique. Atomic force microscopic image of the grown samples exhibit interesting junction architectures in the form of T, Y, and X of small-diameter (∼ 2nm) SWNT bundles. Two-and Two-and Two-and three-terminal measurements on back-gate field effect transistors (FET) fabricated using the CVD grown junctions show interesting pristine metallic behavior and diode-like properties after burning multiple metallic contributing nanotubes.

Current Rectification by As-Grown Chemical Vapor Deposited Single-Walled Carbon Nanotubes

Observation of diode-like current (I) - voltage (V) characteristics of switches fabricated from chemical vapor deposited (CVD) as-grown single-walled carbon nanotube (SWNT) bundles are presented. Atomic force microscopic analysis of the device structure and surface topology of SWNT suggest the observed rectification of current to possibly result from (a) cross-tube junctions, (b) a mixture of metallic and semiconducting tubes in the SWNT bundles, and/or (c) chirality change along a single tube. The exact mechanism underlying the observed rectification could not be established. The diode-like behavior of SWNT devices discovered in this research opens up new applications of SWNTs as nanoscale AC-DC converter.

Scanning tunneling microscope investigation of the current-voltage characteristics of a newly engineered /spl pi/-electron molecule

Current (I)-Voltage (V) characteristics of the self-assembled monolayer (SAM) of /spl pi/-conjugated, 4,4-1,4-phenylenebis(methylidynenitrilo)bisbenzene thiolate (PMNBT) adsorbed on Au (111) substrate have been investigated by scanning tunneling microscopy (STM). The measured tunneling current in the case of PMNBT SAM is much higher than that in the case of dodecanemonothiolate (DDMT) molecules. Furthermore, the PMNBT SAMs appear to exhibit a pronounced rectification of the tunneling current not observed in the case of DDMT. Possible reasons for the difference between the I-V characteristics of the two molecules are identified.