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Exploring the Nanoscale Structures of Atmospheric Plasma Polymerized Films

Rossi Yorimoto, Brenna
http://orcid.org/0000-0002-9341-0839
http://rave.ohiolink.edu/etdc/view?acc_num=akron1689772818527641

Abstract Details

2023, Doctor of Philosophy, University of Akron, Polymer Science.
Plasma polymerization is a facile method of depositing robust films on a wide variety of substrates. While the nanoscale structure of films plasma polymerized in vacuum has been studied some, little is known of the nanoscale structure of the films deposited in the more complex atmospheric plasma polymerized (APP) films. To explore how deposition conditions affect APP film structures, APP films were deposited using hexamethyldisiloxane (HMDSO) precursor at varying power and in varying levels of relative humidity (RH). X-ray and neutron reflectivity measurements reveal that these APP-HMDSO films have a three-layer structure. A transition region of low mass density and carbon content forms next to the substrate as the deposition starts and etching by the plasma initially dominates deposition; a center region which still experiences some etching displays a uniform scattering length density (SLD) with respect to depth; a surface layer next to the air of mass density less than or equal to that of the center region forms whose SLD depends on how “filled in” the layer was when plasma generation was halted. Mass density was found to be sensitive to high humidity, which reduces the flux of monomer fragments to the substrate and allows them to pack more densely. Complementary analysis of depth-resolved X-ray photoelectron spectroscopy and water contact angle measurements show that composition and hydrophilicity are power-dependent. Films deposited at lower power lose more of their carbon to etching, making their composition more silica-like and making them more hydrophilic. Films deposited at higher power retain more of the carbon from the HMDSO monomer thanks to higher deposition rates; a film layer is buried by additional layers before all the residual carbon can be etched away. Neutron reflectivity measurements of the same APP-HMDSO films while exposing them to deuterated solvent vapor showed that vapor easily penetrated them without causing their thickness to increase, indicating that the films are rigid and porous. Ellipsometric refractive index analysis confirmed lower refractive indices among films with lower center layer SLDs, pointing to higher porosities in these films. Though films deposited at higher power have higher porosity, the films deposited at the lowest power took up the most solvent because the etching they experience during deposition carves out more interconnectivity among the pores. The solvent therefore has access to a higher fraction of the pores in films deposited at low power.
Mark Foster (Advisor)
Mesfin Tsige (Committee Chair)
Toshikazu Miyoshi (Committee Member)
Ali Dhinojwala (Committee Member)
Bi-min Newby (Committee Member)
147 p.
Chemistry; Materials Science; Physics; Plasma Physics
APP; PECVD; plasma enhanced chemical vapor deposition; plasma polymerization; plasma polymer; plasma deposition; thin film; reflectivity; reflectometry; X-ray reflectivity; neutron reflectivity

Recommended Citations

Citations

  • Rossi Yorimoto, B. (2023). Exploring the Nanoscale Structures of Atmospheric Plasma Polymerized Films [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1689772818527641

    APA Style (7th edition)

  • Rossi Yorimoto, Brenna. Exploring the Nanoscale Structures of Atmospheric Plasma Polymerized Films. 2023. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1689772818527641.

    MLA Style (8th edition)

  • Rossi Yorimoto, Brenna. "Exploring the Nanoscale Structures of Atmospheric Plasma Polymerized Films." Doctoral dissertation, University of Akron, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=akron1689772818527641

    Chicago Manual of Style (17th edition)

akron1689772818527641
116
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This open access ETD is published by University of Akron and OhioLINK.