Date of Award

2011

Level of Access

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

Advisor

Rosemary L. Smith

Second Committee Member

Scott D. Collins

Third Committee Member

David E. Kotecki

Abstract

Nanofabrication techniques are combined to produce a nanopore (less than 10nm in diameter) in a thin membrane with a pair of nanoelectrodes to address the nanopore. The nanopore is used to localize the DNA in solution while the pair of nanoelectrodes sense molecules as they travel through the nanopore. Sensing DNA is an important step towards using instrumented nanopores as high-speed DNA sequencers. Instrumented nanopores were designed, fabricated, characterized and tested with both DNA and nanoparticles. Devices were visually characterized by electron microscope and atomic force microscopy. The nanoelectrodes conduction mechanisms were investigated by impedance spectroscopy and with quasi-DC current-voltage measurements. The detection of 10nm gold nanoparticles demonstrated high special resolution. Both single and double-stranded DNA were successfully detected in solution. Three new techniques for nanofabrication were developed. The first, solid-phase direct-write (SPDW) is a technique that uses the tip of an atomic force microscope to transfer solid material such as carbon from a source and create sub-100nm features on a surface. The second technique is electron-beam stimulated oxidation of carbon (EBSOC). EBSOC uses an electron beam to locally oxide material in the presence of water vapor or oxygen. As carbon oxides are gaseous, EBSOC leaves behind a pattern defined by the electron beam path. EBSOC can be used to sculpt carbon films down to the single nanometer scale. The third technique is a method for forming nanopores with a low-energy (200eV – 30keV) electron beam. This method uses an electron beam in the presence of a reactive gas (water vapor) to mill nanopores in insulating materials with diameters between 3nm and 20nm. The instrumented nanopore has application to sensing single-molecules or particles in solution (Coulter Counter). If single-base resolution can be achieved, the instrumented nanopore has the potential to dramatically reduce the cost and duration of DNA sequencing. The nanofabrication techniques developed in this work have many applications. In particular, EBSOC is well suited to patterning graphene and carbon nanotubes due to its high resolution and low damage. Low-energy reactive electron beam milling with water vapor is ideal for forming nanopores with diameters below 10nm such as those used for single-molecule devices.

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