Optically-Assisted Scanning Tunneling Microscopy

Scanning tunneling microscopy (STM) consistently provides the highest spatial resolution among the scanning probe methods, allowing surfaces to be investigated on the atomic level. With the addition of optical excitation, STM promises to become a powerful technique for single molecule spectroscopy, enabling one to examine the response of single molecules on a surface. Atomic scale laser-assisted STM has thus far remained an elusive goal, with few recent experiments reaching sub-nanometer resolution. This is due to the many difficulties faced as a result of light perturbing the tunneling junction. The combination of a novel rear-illumination geometry with frequency-modulated laser excitation allows measurement of single molecule optical absorption by detecting modulations in the local electronic density of states with near atomic resolution. This new technique is used to probe the optical absorption of single-walled carbon nanotubes on silicon surfaces, providing data that illustrates unambiguous detection of single molecule optical absorption. Additionally, the deposition of ultrathin gold films is investigated as a potential transparent conductive substrate for use in optical STM experiments performed at visible excitation wavelengths. Roughness is evaluated as a function of film thickness and trends demonstrate a transition from kinetic roughening to thermal roughening that is highly dependent on the deposition temperature profile.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Carmichael, Erin Suzanne

Contributors dc:contributor

• Martin Gruebele

• Chemistry, Physical

Language dc:language

eng

Identifier

(MiAaPQ)AAI3347285

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/84325