Tailored circular Bragg phenomenon in TiO2 sculptured thin films by Post-deposition processing

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Chiral sculptured thin films (STFs) of TiO2 deposited by the serial bi-deposition method can be modified post-deposition to tailor the circular Bragg phenomenon which occurs due to their periodic helical morphology. This post-deposition tailoring is accomplished through annealing and/or wet chemical etching. Annealing of the chiral STF in spectral-hole-filters (SHFs) transforms the material structure from non-crystalline to an anatase structure which is more stable and provides better optical performance. The transformation causes a blue-shift of the circular Bragg phenomenon (CBP) which is quantified and correlated with material properties. Further annealing causes a significant change in morphology, which resembles a "string of pearls", and may be the cause of a loss of transmission. Wet chemical etching is also capable of blue-shifting the Bragg regime of a non-crystalline SHF, while having very little effect on a crystalline SHF. The spectral shift of the Bragg regime is limited by the ability of the nanowires, of which the STFs are composed, to remain attached to the substrate. Wet chemical etching and annealing can be used in combination to allow more control of post-deposition processing.

Original languageEnglish (US)
Title of host publicationNanoengineering
Subtitle of host publicationFabrication, Properties, Optics, and Devices IV
StatePublished - Dec 1 2007
EventNanoengineering: Fabrication, Properties, Optics, and Devices IV - San Diego, CA, United States
Duration: Aug 27 2007Aug 30 2007

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherNanoengineering: Fabrication, Properties, Optics, and Devices IV
Country/TerritoryUnited States
CitySan Diego, CA

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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