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Nanomaterials 2018, 8(6), 365; https://doi.org/10.3390/nano8060365

Investigating the Trimethylaluminium/Water ALD Process on Mesoporous Silica by In Situ Gravimetric Monitoring

1
BasCat—UniCat BASF JointLab, Technische Universität Berlin, Hardenberstraße 36, 10623 Berlin, Germany
2
Institut für Chemie, Technische Universität Berlin, Straße des 17, Juni 135, 10623 Berlin, Germany
3
Process Research and Chemical Engineering, BASF SE, Carl-Bosch-Straße 38, 67056 Ludwigshafen, Germany
*
Author to whom correspondence should be addressed.
Received: 24 April 2018 / Revised: 19 May 2018 / Accepted: 21 May 2018 / Published: 24 May 2018
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Abstract

A low amount of AlOx was successfully deposited on an unordered, mesoporous SiO2 powder using 1–3 ALD (Atomic Layer Deposition) cycles of trimethylaluminium and water. The process was realized in a self-built ALD setup featuring a microbalanceand a fixed particle bed. The reactor temperature was varied between 75, 120, and 200 °C. The self-limiting nature of the deposition was verified by in situ gravimetric monitoring for all temperatures. The coated material was further analyzed by nitrogen sorption, inductively coupled plasma-optical emission spectroscopy, powder X-ray diffraction, high-resolution transmission electron microscopy, attenuated total reflection Fourier transformed infrared spectroscopy, and elemental analysis. The obtained mass gains correspond to average growth between 0.81–1.10 Å/cycle depending on substrate temperature. In addition, the different mass gains during the half-cycles in combination with the analyzed aluminum content after one, two, and three cycles indicate a change in the preferred surface reaction of the trimethylaluminium molecule from a predominately two-ligand exchange with hydroxyl groups to more single-ligand exchange with increasing cycle number. Nitrogen sorption isotherms demonstrate (1) homogeneously coated mesopores, (2) a decrease in surface area, and (3) a reduction of the pore size. The experiment is successfully repeated in a scale-up using a ten times higher substrate batch size. View Full-Text
Keywords: atomic layer deposition; ALD; in situ gravimetric; mesoporous silica; ligand exchange; fixed bed; particle coating atomic layer deposition; ALD; in situ gravimetric; mesoporous silica; ligand exchange; fixed bed; particle coating
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Strempel, V.E.; Knemeyer, K.; Naumann d’Alnoncourt, R.; Driess, M.; Rosowski, F. Investigating the Trimethylaluminium/Water ALD Process on Mesoporous Silica by In Situ Gravimetric Monitoring. Nanomaterials 2018, 8, 365.

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