Potassium Hexafluoroacetylacetonate Complex with 18-Crown-6 Ether as a Volatile Precursor of Molecular and Inorganic Films: Thermal and Structural Insights

TL;DR

A new volatile potassium complex is developed for making molecular and inorganic films, with insights into its thermal and structural properties.

Contribution

The study introduces a novel volatile potassium complex suitable for MOCVD, enabling the production of potassium-containing films.

Findings

The complex K(18C6)(hfac) exhibits a molecular structure and volatility suitable for gas-phase synthesis.

Potassium fluoride forms with oxygen and interacts with silicon substrates, while water vapor reduces fluorine content.

The complex allows for the first-time MOCVD production of potassium-containing films from a fluorinated precursor.

Abstract

Volatile coordination compounds are widely used as precursors for the gas phase synthesis of functional materials. However, such complexes are still very rare for alkali metals, especially for heavy representatives of this family (potassium, rubidium, cesium) due to the tendency to form polymeric structures. This work is devoted to the exploration of a potassium hexafluoroacetylacetonate complex with 18-crown-6 ether, K(18C6)(hfac), as a unique volatile precursor with an isolated molecular structure. A convenient synthesis procedure was developed, and key structural features were identified including temperature-dependent effects. The thermal properties of the complex were studied via thermogravimetry and measurements of saturated vapor pressure using the Knudsen effusion method with mass spectrometric registration of the gas phase composition. Both from solution and the gas phase, the molecular films of K(18C6)(hfac) obtained exhibit a strictly (h00) orientation, where half of the surface cations have a coordination sphere accessible to supramolecular contacts. For the first time, the possibility of producing potassium-containing films from a fluorinated precursor by metal–organic chemical vapor deposition (MOCVD) has been demonstrated. With oxygen as the reactant gas, potassium fluoride forms and interacts with the silicon substrate, while introducing water vapor significantly reduces the fluorine content, suggesting its suitability for the preparation of oxide films.

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