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Dissertation/Thesis Abstract

Ultrathin, Continuous Platinum Atomic Layer Deposition on High Surface Area Substrates, and Mass Spectrometer Characterization of Volatile Etch Species Produced during Thermal Al2O3 Atomic Layer Etching: Studies in Atomic Scale Materials and Processing
by Clancey, Joel William, Ph.D., University of Colorado at Boulder, 2019, 141; 13902451
Abstract (Summary)

Atomic scale materials and processes can advance technology in a wide range of areas, including electrocatalysts for fuel cells, and the manufacture of complex logic and memory devices for smart grid energy systems and mobile computing. Two such atomic scale techniques are atomic layer deposition (ALD) and thermal atomic layer etching (ALE). In two sections, this thesis investigates the use of ALD and thermal ALE to improve materials at the atomic scale and provide mechanistic insight:

I. Use of adhesion layers with plasma-assisted ALD to deposit ultrathin, continuous Pt ALD films on high surface area substrates for improved polymer electrolyte membrane fuel cell (PEMFC) electrocatalysts

II. Use of in situ quadrupole mass spectrometry (QMS) to characterize volatile etch species during thermal Al2O3 ALE

The first section describes the chemistry involved in using WALD adhesion layers prior to plasma-assisted ALD to conformally coat TiO2 nanoparticles and 3M nanostructured thin film (NSTF) with continuous, ultrathin films of Pt ALD. Transmission electron microscopy (TEM) revealed the Pt ALD films to be conformal and continuous on the TiO2 nanoparticle and 3M NSTF supports with a thickness of ~3-4 nm. Ex situ X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and powder X-ray diffraction were used to study the composition and crystallinity of the Pt ALD films.

The second section describes the design and use of a custom ALE reactor with in situ QMS to identify the volatile etch species produced during thermal Al2O3 ALE. Thermal ALE uses fluorination and ligand-exchange reactions to produce volatile etch species. In situ QMS results showed the major etch species produced by reacting Al(CH3)3 (TMA) with HF-fluorinated Al2O3 and AlF3 powder at 300 °C were F,CH3- and F,F-bridged Al dimers and trimers. In situ QMS showed that the reaction of AlCl(CH3)2 (DMAC) with AlF3 powder at 300 °C produced the same Al dimers and trimers with minor mixed Cl,F-bridged dimer and trimers. In situ QMS also revealed that reacting SiCl4 and TiCl4 with AlF3 powder at 300 °C and 250 °C respectively, did not produce Al-based etch species, but rather showed evidence of ligand-exchange with the AlF3 surface

Indexing (document details)
Advisor: George, Steven M.
Commitee: Sharma, Sandeep
School: University of Colorado at Boulder
Department: Chemistry
School Location: United States -- Colorado
Source: DAI-B 81/3(E), Dissertation Abstracts International
Subjects: Chemistry, Nanoscience, Materials science
Keywords: Atomic layer deposition, Plasma-assisted atomic layer Deposition, Quadrupole mass spectrometry, Thermal atomic layer etching, Thermal atomic layer etching volatile etch products, Ultrathin Platinum
Publication Number: 13902451
ISBN: 9781088302538
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