Thin Film Formation Based on a Nanoporous Metal-Organic Framework by Layer-By-Layer Deposition.

Autor: Fratschko M; Institute of Solid State Physics, Graz University of Technology, Graz 8010, Austria., Zhao T; Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany., Fischer JC; Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany., Werzer O; Department Materials, Joanneum Research Forschungsgesellschaft mbH, Weiz 8160, Austria., Gasser F; Institute of Solid State Physics, Graz University of Technology, Graz 8010, Austria., Howard IA; Institute of Microstructure Technology, Karlsruhe Institute of Technology, Karlsruhe 76131, Germany., Resel R; Institute of Solid State Physics, Graz University of Technology, Graz 8010, Austria.
Jazyk: angličtina
Zdroj: ACS applied nano materials [ACS Appl Nano Mater] 2024 Nov 01; Vol. 7 (22), pp. 25645-25654. Date of Electronic Publication: 2024 Nov 01 (Print Publication: 2024).
DOI: 10.1021/acsanm.4c04763
Abstrakt: Understanding the structure of thin films is essential for successful applications of metal-organic frameworks (MOFs), such as low k-dielectrics in electronic devices. This study focuses on the thin film formation of the 3D nanoporous MOF Cu 2 (bdc) 2 (dabco). The thin films are prepared by a layer-by-layer technique with varying deposition cycles (1 to 50). Thin film morphologies and crystallographic properties were investigated using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, and grazing-incidence X-ray diffraction (GIXD). AFM revealed an island growth (Volmer-Weber) with plate-like shaped islands. FTIR and GIXD revealed that Cu 2 (bdc) 2 (dabco) crystals form already during the first preparation cycle. The heights of the islands do not increase linearly with the number of deposition cycles, suggesting multiple growth stages. X-ray diffraction pole figures uncover a uniplanar texture of the Cu 2 (bdc) 2 (dabco) crystals, together with randomly oriented crystallites. The fraction of uniplanar oriented crystals increases with each deposition cycle, reaching a maximum of 75% at ten deposition cycles, simultaneously achieving complete substrate coverage. However, already at five cycles, an additional phase of randomly oriented copper-terephthalate (Cu 2 (bdc)) crystals appeared; this phase reaches a fraction of 22% at the largest film thickness (50 cycles). In summary, a detailed understanding of the thin film formation of an archetypal layer-pillar MOF is presented, elucidating how films grow in terms of their morphology and crystalline properties. Samples prepared by ten cycles show complete coverage of the substrate together with the highest degree of preferred crystal orientation. These results establish a deepened understanding of critical parameters for MOF thin film applications, such as complete substrate coverage and definition of the nanopores relative to the substrate surface.
Competing Interests: The authors declare no competing financial interest.
(© 2024 The Authors. Published by American Chemical Society.)
Databáze: MEDLINE
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