Irradiation Accelerated Hydrolysis of Soluble Keplerate Titanium–Bismuth Oxo Clusters with Complete Surface Ligands Exchange Behavior for Direct Oxides Nanopatterning

Abstract

Controlled hydrolysis of metal oxo clusters has been first applied as a direct nanopatterning strategy for oxide materials. A heterometallic Bi₄Ti₁₂ oxo cluster is constructed with Keplerian-type architecture as a molecular platform for post-synthetic reactivity studies. Detailed mass spectrometry analysis confirms its exceptional dissolution stability and complete surface alkoxy ligands exchangeability. Interestingly, spin-coated thin films of Bi₄Ti₁₂ oxo clusters exhibit significant solubility contrast after ambient condition hydrolysis. Accordingly, electron-beam irradiation is applied to accelerate the cluster hydrolysis in exposed areas to enable fine lines patterning, with the hydrolysis-condensation pathways of irradiated Bi₄Ti₁₂ oxo clusters being demonstrated by comparative spectroscopic analyses. Finally, 20 nm critical dimension (CD) lines can be fabricated using this method under an expose energy of 130 µCcm⁻². Therefore, this work not only constructs a Keplerate cluster family with interesting complete surface ligand exchange behavior, but also provides a new metal hydrolysis-driven lithography strategy for the direct patterning of metal oxide nanostructures.