A Correlated Analysis of Defect in Nanostructures with TEM Inspection and Electrical Characterization
Date Issued
2012
Date
2012
Author(s)
Lan, Yann-Wen
Abstract
In this doctoral dissertation, we have developed a set of novel tool and a specific chip for a correlated study of defect based on electrical measurements and electron microscope imaging. Both of experimental details addressing these techniques are meticulously presented. In the former, a moveable carbon nanotube (CNT) cantilever gate is developed for the detection of embedded charge defects in suspended nanowires. The CNT gate is composed of a gold probe welded to a thick carbon nanotube which is in turn attached to a thinner carbon nanotube. It can not only detect embedded Ga ions in the suspended nanowires as well as trapped electrons, but also determine the polarity of the embedded ions and measure the amount of trapped electrons, respectively. The technique can be extended to other types of suspended nanowires. In the latter, a through-hole chip with suspended electrodes is fabricated to be a platform. This allows a physical correlation to be established for transmission electron microscopy inspection and electrical characterization. For demonstration purpose, the single-walled carbon nanotube bundles are placed on top of suspended electrodes by manipulators and we report the effects of oxygen doping on the electrical properties of defective metallic and semiconducting carbon nanotube bundles on the through-hole chip. Carbon vacancies are generated by electron beam knock-out process, which can be clearly examined by transmission electron microscopy. The dangling carbon bonds of the vacancies are very active and can easily adsorb oxygen molecules. In terms of the semiconducting bundles, oxygen bonding lowers the bandgap and the original p-type bundles thereby modifying them to become bi-polar. For the metallic bundles, a hysteretic bi-stable state in gate-voltage cycling is observed; this is attributed to the electrically controlled dipole field of the oxygen molecules.
Subjects
carbon nanotube
defect
nanowires
transmission electron microscopy
bi-polar
bi-stable
Type
thesis
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