Inorganic Phototropism: Emergent Properties Directing Growth of Mesostructured Semiconductors

Author: Meier, Madeline Claire

Year: 2023

Degree: Dissertation (Ph.D.)

Advisor: Lewis, Nathan Saul

Committee Members: Gray, Harry B.; Faber, Katherine T.; Blake, Geoffrey A.; Lewis, Nathan Saul

Option: Chemistry

DOI: 10.7907/rqwq-tv81

Abstract

Nature exhibits emergent growth phenomena where in neighboring features result in ensemble effects that direct the overall growth morphologies. Plants, such as palm trees, display phototropism where-in the crown grows toward the time weighted average position of the sun to optimize solar collection. A methodology, known as inorganic phototropic growth, utilizes a similar mechanism with the incident illumination during electrochemical deposition directing the growth of mesostructured semiconductors. This photoelectrochemical deposition process, generates highly anisotropic, periodic lamellar features resulting in the capability to fabricate nanostructured features over macroscopic areas. The process is lithography-free and uses no templates or directing agents of any kind and relies solely on the incident illumination to direct semiconductor growth. In this thesis, the nanophotonic phenomena and emergent synergistic absorption that drives the inorganic phototropic growth process was investigated using unconstrained and confined susbtrates. Additionally, the impact of inclined, off-normal incident illumination on the evolution of structure morphology was investigated for patterned and isotropic substrates revealing the mechanism behind the non-monotonic relationship between incident angle and observed out-of-plane orientation for unconstrained substrates.

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