Nanopantography With Removable Membrane-Based Electrostatic Lens Arrays

Sawadichai, Ryan

Nanopantography With Removable Membrane-Based Electrostatic Lens Arrays

dc.contributor.advisor	Donnelly, Vincent M.
dc.contributor.advisor	Economou, Demetre J.
dc.contributor.committeeMember	Nikolaou, Michael
dc.contributor.committeeMember	Ruchhoeft, Paul
dc.contributor.committeeMember	Bao, Jiming
dc.creator	Sawadichai, Ryan
dc.creator.orcid	0000-0002-0157-7907
dc.date.accessioned	2022-06-29T22:30:48Z
dc.date.created	May 2021
dc.date.issued	2021-05
dc.date.submitted	May 2021
dc.date.updated	2022-06-29T22:30:49Z
dc.description.abstract	Nanopantography is a method for massively parallel writing of nano-sized patterns using an ion beam. In this process, a broad area, collimated, nearly-monoenergetic ion beam is directed towards an array of micron-scale electrostatic lenses in direct contact with a substrate. By applying an appropriate DC voltage to the lens array with respect to the substrate, the ion beamlet entering each lens converges to a fine spot that can be 100 times smaller than the diameter of each lens. Previously, lenses fabricated directly on the silicon substrate were used to etch 3 nm diameter holes in silicon by exposure to a monoenergetic Ar+ ion beam and chlorine gas. This work reports on the development of removable and reusable free-standing membrane-based electrostatic lens arrays that are designed to pattern any conducting surface. The lens arrays are fabricated on a silicon wafer coated with PMGI, SU-8, gold, copper, and PMMA. Lens openings are lithographically defined, and an acrylic frame is placed over the array. The lens patterns are etched through the SU-8 and the membrane is released by dissolution of the PMGI layer. The applied voltage used to focus the ion beamlets also serves to electrostatically clamp the lens array to a conducting substrate, which is observed as a flattening of the membrane against the substrate surface and an increasing capacitance measured between the lens array and the substrate. An array with lens diameters between 0.8 μm and 1.5 μm was used to pattern features as small as 20 nm on a silicon substrate using a 70 eV Ar+ ion beam. Ion trajectory simulations were to understand the sensitivity of minimum feature size to the variation of lens potential, lens aspect ratio, and lens size. Simulations for this lens geometry agreed with the experimentally observed results when chromatic and spherical aberrations are considered. Based on the simulation results, it should be possible to print much smaller features via a step and repeat process with a thinner dielectric and narrow lens diameter. Diagnostics of a positive ion beam extracted from a pulsed oxygen plasma were conducted, confirming that the majority of the beam consists of 100 eV O2+ ions. Patterning of graphene with the nanopantography method was conducted with the O2+ ion beam, resulting in defect production in a focused spot 17 times smaller than the lens openings.
dc.description.department	Chemical and Biomolecular Engineering, William A. Brookshire Department of
dc.format.digitalOrigin	born digital
dc.format.mimetype	application/pdf
dc.identifier.uri	https://hdl.handle.net/10657/10185
dc.language.iso	eng
dc.rights	The author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).
dc.subject	plasma
dc.subject	plasma processing
dc.subject	ion beam
dc.subject	nanopantography
dc.subject	plasma etching
dc.title	Nanopantography With Removable Membrane-Based Electrostatic Lens Arrays
dc.type.dcmi	Text
dc.type.genre	Thesis
local.embargo.lift	2023-05-01
local.embargo.terms	2023-05-01
thesis.degree.college	Cullen College of Engineering
thesis.degree.department	Chemical and Biomolecular Engineering, William A. Brookshire Department of
thesis.degree.discipline	Chemical Engineering
thesis.degree.grantor	University of Houston
thesis.degree.level	Doctoral
thesis.degree.name	Doctor of Philosophy