Amphoteric Aqueous Hafnium Cluster Chemistry.
Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography.
Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA.
Sara
S
Goberna-Ferrón
Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA.
Deok-Hie
DH
Park
Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA.
Jenn M
JM
Amador
Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA.
Douglas A
DA
Keszler
Center for Sustainable Materials Chemistry (CSMC) and Department of Chemistry, Oregon State University, Corvallis, OR, 97331-4003, USA. may.nyman@oregonstate.edu.
May
0000-0002-1787-0518
M
Nyman
cluster compounds; hafnium; mass spectrometry; peroxides; small-angle X-ray scattering