Nb2O5 and Ta2O5 Thin Films from Polyoxometalate Precursors: A Single Proton Makes a Difference

Fullmer, Lauren B.; Mansergh, Ryan H.; Zakharov, Lev N.; Keszler, Douglas A.; Nyman, May

doi:10.1021/acs.cgd.5b00508

Cited by 59 publications

(65 citation statements)

References 27 publications

(34 reference statements)

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“…QAAs first utilized in POM chemistry are simple tetraalkyl ammoniums including tetramethyl (TMA), tetrabutyl (TBA) and tetrahexyl (THA) ammonium that can modulate solubility of POMs. TMA is a notoriously “innocent” counterion that does not promote aggregation and allows high solubility and stability in water, particularly for polyoxoniobates and tantalates . On the other hand, TBA and THA have been commonly used for decades to extract (or precipitate) POMs into nonaqueous solvents for numerous purposes including electrochemical studies and applications involving POM redox chemistry, catalytic studies in organic solvents, and to stabilize water‐ or pH‐sensitive POMs .…”

Section: Supramolecular Pom‐cation Aggregation Leading To Soft Mattermentioning

confidence: 99%

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Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

et al. 2019

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Polyoxometalates (POMs) are molecular metal‐oxide anions applied in energy conversion and storage, manipulation of biomolecules, catalysis, as well as materials design and assembly. Although often overlooked, the interplay of intrinsically anionic POMs with organic and inorganic cations is crucial to control POM self‐assembly, stabilization, solubility, and function. Beyond simple alkali metals and ammonium, chemically diverse cations including dendrimers, polyvalent metals, metal complexes, amphiphiles, and alkaloids allow tailoring properties for known applications, and those yet to be discovered. This review provides an overview of fundamental POM–cation interactions in solution, the resulting solid‐state compounds, and behavior and properties that emerge from these POM–cation interactions. We will explore how application‐inspired research has exploited cation‐controlled design to discover new POM materials, which in turn has led to the quest for fundamental understanding of POM–cation interactions.

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Section: Supramolecular Pom‐cation Aggregation Leading To Soft Mattermentioning

confidence: 99%

“…It is tempting to correlate this behavior with the pH‐stability of the POMs; however, note that the alkaline‐stable uranyl peroxide POMs exhibit normal solubility behavior . The Nb/Ta POMs are also highly water‐soluble as tetramethylammonium (TMA) salts …”

Section: Introduction: Fundamentals Of Pom–cation Interactionsmentioning

confidence: 99%

Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

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“…Betrachtet man jedoch die unter basischen Bedingungen stabilen Uranylperoxid‐POMs, zeigen diese das erwartete, normale Löslichkeitsverhalten . Zudem ist zu beachten, dass Nb/Ta‐POMs als Tetramethylammonium (TMA)‐Salze ebenfalls sehr gut wasserlöslich sind …”

Section: Einleitung: Grundlagen Der Pom‐kation‐wechselwirkungenunclassified

“…Anfänglich wurden in der POM‐Chemie meist einfache Tetraalkylammonium‐Verbindungen wie Tetramethylammonium (TMA), Tetrabutylammonium (TBA) und Tetrahexylammonium (THA) genutzt, um die POM‐Löslichkeit einzustellen. TMA ist ein bekanntes “unschuldiges” Kation, das nicht zur POM‐Aggregation führt und hohe Löslichkeit und Stabilität in wässriger Lösung ermöglicht, besonders für Niobate und Tantalate . Zudem wurden TBA und THA oft genutzt, um POMs in nichtwässrige Lösungen zu extrahieren (oder zu fällen).…”

Section: Supramolekulare Pom‐kation‐aggregation Zur Bildung Weicher Munclassified

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Jenseits von Ladungsausgleich: Gegenkationen in der Polyoxometallat‐Chemie

et al. 2019

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Polyoxometallate (POMs) sind molekulare Metalloxidanionen, die Anwendung in Energiewandlung und ‐speicherung, biomolekularer Chemie sowie Materialdesign und ‐integration finden. Das Wechselspiel von intrinsisch anionischen POMs mit organischen oder anorganischen Gegenionen wird häufig übersehen, ist jedoch essenziell, um die Aggregation, Stabilisierung, Löslichkeit und Funktion von POMs zu verstehen. Jenseits von einfachen Alkalimetall‐ oder Ammoniumkationen können neuartige Anwendungen durch vielseitige Kationen wie Dendrimere, mehrwertige Metallkationen, Metallkomplexe, Amphiphile oder Alkaloidkationen erzielt werden. Dieser Aufsatz gibt einen Überblick über grundlegende POM‐Kation‐Wechselwirkungen in Lösung, die daraus resultierenden Festkörperstrukturen und bespricht neuartige Reaktivitäten und Eigenschaften, die aus diesen Wechselwrkungen resultieren. Wir untersuchen, wie anwendungsnahe Forschung das Kation‐kontrollierte Design neuartiger POM‐Materialien ermöglicht hat, was wiederum den Wunsch nach der Aufklärung der Grundlagen von POM‐Kation‐Wechselwirkungen angeregt hat.

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Amphoteric Aqueous Hafnium Cluster Chemistry

et al. 2016

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Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxidee nables extreme UV lithographic patterning of sub-10 nm HfO 2 structures.H afnium speciation under these basic conditions (pH > 10), however,i su nknown, as studies of hafnium aqueous chemistry have been limited to acid. Here,w er eport synthesis,crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA] 6 [Hf 6 (m-O 2 ) 6 (m-OH) 6 (OH) 12 ]·38 H 2 O. The solution behavior of the cluster,i ncluding supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens anew chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing ac ritical process in single-digit-nm lithography.Water-soluble molecular oxo-hydroxo metal clusters are recognized building blocks for deposition of functional thinfilm coatings,offering low energy and "green" processing. [1][2][3] Additionally,s elected hafnium-peroxo-sulfate clusters provide unprecedented dimensional control in nanolithography. [4,5] In this lithography,u nexposed oxo-hydroxo Hf regions dissolve in base,m eaning soluble hafnium species exist at high pH.Up to now,h owever,t he aqueous chemistry of hafnium has been documented only for strongly acidic conditions.I n mildly acidic conditions (pH ! 3), gels and precipitates result from rapid hydrolysis and condensation. [6,7] At low pH, oxohydroxo hafnium clusters are commonly stabilized and isolated with capping sulfate ligands,s ometimes linking clusters into 1, 2o r3 -dimensional networks.[ [12,13] Our interest in oxo-hydroxo hafnium speciation in base arises from the development step in lithographic patterning with the water-processed hafnium material known as HafSO x , formulated Hf 4 (OH) 6.4 (O 2 ) 2 (SO 4 ) 2.8 . [4,5,14] Nanolithography allows bulk semiconductors and metals to be shaped into computing devices with sub-10 nm features.[15] New inorganic resists,such as HafSO x ,offer ultra-high-resolution patterns. [6] There are two major steps in the patterning process with HafSOx:1)exposure,which causes dissociation of the peroxo ligand and induces condensation;and 2) development, where unexposed material is selectively dissolved in concentrated aqueous tetramethylammonium hydroxide (TMAH). The nature of the species produced in these basic solutions is unknown. This dissolution, coupled with stability of asimilar peroxo-phosphato-niobium cluster observed in both basic and acidic solutions [16] has led us to propose the concept of amphoteric clusters,w herein simple ligand sets stabilize as ingle cluster or similar clusters at the extreme ends of the pH scale.T his concept broadens the approach to cluster synthesis and study,asmost common cluster types exist across limited pH ranges.[17] Forexample,Group 13 polycations are currently known to exist in the narrow range pH 3-4; [18,19] V, Mo,and Wpolyoxom...

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Nb₂O₅ and Ta₂O₅ Thin Films from Polyoxometalate Precursors: A Single Proton Makes a Difference

Cited by 59 publications

References 27 publications

Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

Beyond Charge Balance: Counter‐Cations in Polyoxometalate Chemistry

Jenseits von Ladungsausgleich: Gegenkationen in der Polyoxometallat‐Chemie

Amphoteric Aqueous Hafnium Cluster Chemistry

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