Record Details
Liquid-gated carbon nanotube transistor noise sources and sensitivity limits
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Liquid-gated carbon nanotube transistor noise sources and sensitivity limits |
| Names |
Sharf, Tal
(creator) Minot, Ethan (advisor) |
| Date Issued | 2014-08-27 (iso8601) |
| Note | Graduation date: 2015 |
| Abstract | Low-dimensional electronic materials offer a platform to observe biological processes with unprecedented spatial and temporal resolution. Carbon nanotubes (CNTs) are the closest physical analog to an ideal 1D system and can be scaled and integrated into multiplexed electronic circuitry. The molecular structure of a CNT is also biocompatible, making them an ideal platform to simultaneously interface and interrogate the biological world at the nanometer scale. The major theme of this dissertation is the investigation of the physical origins of electronic signals produced in CNT field-effect transistors (FETs) in physiological environments. Electronic signals measured in CNT FET biosensors are the result of electrostatic changes in the environment surrounding the CNT. Biological molecules in close proximity to a CNT can dominate the local electrostatic landscape surrounding it. The activity of these biological molecules can in turn modulate electronic transport in 1D CNT systems. The sensitivity of CNT FETs is ultimately limited by ever-present noise in the electrostatic environment. This noise is often due to the stochastic fluctuation of charge traps, which are inherent to nanometer scale material interfaces at ambient conditions. In order to push the detection limits of CNT FETs and enhance our ability to resolve biological signals, we must first minimize this unwanted noise. In order probe the major sources of noise in CNT FETs, we have systematically controlled the environment surrounding a CNT. We quantify the noise generated by the substrate, surface adsorbates, and biological molecular interactions with a CNTs surface. We show that electrostatically induced disorder at the CNT interface is a significant source of parasitic noise. By removing the substrate interaction and surface adsorbates, we find a 19-fold reduction in the power spectrum of electronic noise. To further investigate the microscopic origins of noise, we examine a correlation between the protonation state of charged biological moieties at the CNT interface and the magnitude of electronic noise. In some cases, the electrostatic perturbation generated by a single charge trap in close proximity to a CNT can dominate the noise in a CNT FET. The charge trap creates a scattering site in the CNT. When the trap is occupied, device conductance can be significantly reduced, leading to random telegraph signals (RTS), in constant-bias current. We experimentally and theoretically demonstrate that the amplitude of the RTS depends strongly on the Fermi energy and polarity of the free carriers. The high signal-to-noise ratio that we observe demonstrates that it is possible to detect the fields generated by the fluctuations of a single electron charge at room temperature. |
| Genre | Thesis/Dissertation |
| Topic | Carbon nanotube |
| Identifier | http://hdl.handle.net/1957/52282 |
