Event Information
Controlling Diameters and Transport Properties of Carbon Nanotubes by Synthesis and Chemical Modification
- Abstract:
- The research on carbon nanotubes has emerged to be one of the most active fields in the past decade. This seminar will present the research progress that has been made on controlling diameters of carbon nanotubes, separating metallic and semiconducting carbon nanotubes in their thin film devices and studying the effects that the channel lengths of nanotube thin film field effect transistors (FETs) have on their response to electric gating.
Uniform and very small single-walled carbon nanotubes (SWNTs) have been successfully synthesized by using identical giant inorganic metal-containing nanoclusters as catalysts. The diameters of SWNTs closely resemble the sizes of the nanoclusters. The average diameter of the SWNTs grown using this method is 1 nm and the standard deviation is about 17%. The method represents the first time that identical molecules have been used as catalysts for growth of SWNTs and produced the most uniform SWNTs at the time that the paper was published.
Semiconducting-only nanotube thin film devices have been successfully fabricated by using diazonium reagents to selectively eliminate metallic carbon nanotubes in the devices. Nanotube thin films always consist of both metallic and semiconducting nanotubes and it is problematic when they are integrated into electronic devices because metallic nanotubes are normally undesired for field effect transistors or chemical sensors. The approach we developed represents the easiest way to separate metallic and semiconducting carbon nanotubes in their thin film devices by making metallic nanotubes insulating. This will greatly enhance the performance of the nanotube thin film devices. We also found out that the concentrations of the diazonium reagents and the diameters of the carbon nanotubes are critical factors for this reaction.
The channel lengths of nanotube thin film FETs have a large impact on their response to electric gating because they will determine the number and the type of nanotube-nanotube junctions that form the conducting paths between the electrodes. More individual metallic nanotubes and more transport paths with only metallic-metallic nanotube junctions can cross smaller channel lengths and do not have a strong response to electric gating. However, when the channel lengths become very small compared with the average length of the nanotubes, the dominant conducting components will be individual nanotubes rather than nanotube junctions.
Student Exams Seminar