Tailoring nanopore formation in atomic layer deposited ultrathin films [Nanopore formation in atomic layer deposited ultrathin films]

Journal Article · Wed Nov 15 04:00:00 EST 2017 · Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films

DOI:https://doi.org/10.1116/1.5003360· OSTI ID:1471590

Karwal, Saurabh ^[1]; Li, Tao ^[2]; Yanguas-Gil, Angel ^[2]; Canlas, Christian P. ^[2]; Lei, Yu ^[3]; Mane, Anil U. ^[2]; Libera, Joseph A. ^[2]; Seifert, Soenke ^[2]; Winans, Randall E. ^[2]; Elam, Jeffrey W. ^[2]

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1. Univ. of Technology Eindhoven (Eindhoven)
2. Argonne National Lab. (ANL), Argonne, IL (United States)
3. Univ. of Alabama in Huntsville, Huntsville, AL (United States)

Selectivity is a critical attribute of catalysts used in manufacturing of essential and fine chemicals. An excellent way to induce selectivity in catalysts is by using ultrathin films with tailored nanoporosity. For instance, nanopores can be created in atomic layer deposition (ALD) ultrathin over-coatings on supported metal nanoparticles by subjecting the coatings to high temperature annealing. These nanopores expose the active surface of the underlying metal nanoparticles. The dimensions of these nanopores can be tuned to impart shape selectivity: only reactants or products with a specific size or shape can fit inside the pore. In this work, the authors explore the underlying mechanism driving nanopore formation in ALD films. Ultrathin films of ALD TiO₂ (similar to 2.5 nm thick) and ALD Al₂O₃ (similar to 4.9 nm thick) were deposited on nonporous gamma-Al₂O₃ nanoparticles. The pore formation and evolution were monitored in situ during thermal annealing using small-angle x-ray scattering (SAXS), and the crystallinity was monitored by in situ x-ray diffraction. A correlation between the nanopore formation and amorphous to crystalline phase transitions in the ALD layers was observed. The authors hypothesize that the pores form through the relaxation of stress induced by densification of the ALD films during the phase transitions. In conclusion, the authors developed a mathematical model to evaluate this hypothesis and found remarkable agreement between the model and the SAXS measurements.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Institute for Atom-efficient Chemical Transformations (IACT); Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1471590
• Alternate ID(s): OSTI ID: 1421079
• Journal Information: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Journal Name: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films Journal Issue: 1 Vol. 36; ISSN 0734-2101
• Publisher: American Vacuum Society
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY