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Growth Towards Light: Translation of Optical Inputs into Mesostructured Outputs via Inorganic Phototropism


Carim, Azhar Iqbal (2021) Growth Towards Light: Translation of Optical Inputs into Mesostructured Outputs via Inorganic Phototropism. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/mn62-wc26.


Palm trees exhibit phototropic growth wherein physical extension of the plant guides the crown towards the time-averaged position of the sun to maximize solar harvesting. In analogous fashion, the directed growth and resultant nanoscale morphology of an evolving inorganic semiconductor deposit can be precisely defined in three-dimensional space using incoherent, uncorrelated light with spatially-invariant intensity. Maskless, photo-driven electrochemical deposition of semiconductor films generates highly ordered, periodic mesostructures with anisotropic, nanoscale features conformally over macroscale areas. This inorganic phototropic growth process does not utilize any physical nor chemical templating agents. Rather, as with natural phototropism, wherein the morphological phenotype expressed by an organism is a function of the light available in the habitat during growth, the precise mesostructures are set by the deposition illumination. Structural complexity and anisotropy result as consequences of inherent asymmetry in the light-material interactions during growth. Here, the morphological outcomes defined by specific illumination inputs are explored and the microscopic optical phenomena underpinning this physical recording of light information is interrogated via both experimental and computational methodologies.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:nanoscale, nanostructure, mesoscale, mesostructure, phototropic, phototropism, electrodeposition, electrochemistry, photoelectrochemistry, semiconductor, photonic, self-organization
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lewis, Nathan Saul
Thesis Committee:
  • Blake, Geoffrey A. (chair)
  • Gray, Harry B.
  • Rossman, George Robert
  • Lewis, Nathan Saul
Defense Date:28 January 2021
Funding AgencyGrant Number
National Science Foundation Graduate Research FellowshipDGE-1144469
Department of Energy (DOE)DE-SC0001293
Record Number:CaltechTHESIS:04202021-164652779
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Ch.3 adapted for Ch.4 adapted for Ch.5 publication publication publication publication publication
Carim, Azhar Iqbal0000-0003-36306872
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14124
Deposited By: Azhar Carim
Deposited On:03 Jun 2021 23:50
Last Modified:27 Oct 2021 23:41

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