Today, in recognition of Doug Keszler’s many contributions to Chemistry of Materials, I will present three metal-oxo cluster chemistries that we have developed in the Center for Sustainable Materials Chemistry (CSMC). These include: 1) hafnium peroxide clusters, 2) alkyl tin clusters, and 3) a chromium aluminum zinc polyoxocation. Collectively, these cluster chemistries elucidate the importance of polynuclear metal-oxo species in nanolithography, and develop the foundation for mechanistic growth strategies of metal oxides from water. Solution characterization is foundational for all studies, including small-angle X-ray scattering (SAXS), electrospray ionization mass spectrometry (ESI MS), multinuclear Nuclear Magnetic Resonance spectrometry, and Raman spectroscopy. Hafnium peroxide sulfate (HafSOx; one of the founding chemistries of the CSMC) acidic precursor solutions produce the smallest lithographic features to date that are patterned by light. We elucidate the hafnium-oxo cluster speciation in both the acidic deposition solution and the alkaline development solution; especially the role of peroxide in Hf-oxo cluster speciation. Moreover, we show that clusters can be obtained from the extreme ends of the pH scale, which we have dubbed ‘amphoteric clusters’. We also are developing non-aqueous cluster-based solution chemistry for lithography with alkyl tin species. Here we present new alkyl tin cluster topologies, as well as strategies for improving cluster dissolution and precipitation behavior, in order to optimize film smoothness and density. Finally, we have developed a synthetic pathway to isolate hydrolytically unstable clusters, and we have used it to obtain Cr-containing polycationic Keggin ions. The self-assembly pathway that we have elucidated completely bypasses the metastable aqueous state in which fully-formed clusters dominate the solution. Once obtained, the clusters can be redissolved in water and remain stable, allowing for further manipulation or employment in growth of materials from water.<br/>

Metal-oxo clusters from across the periodic table

253rd National Meeting (2017)

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