Enhancing Thermal Stability and Volatility of Barium Complexes through Cyclic Nitrogen-Containing Auxiliary Ligands

Area of Science:

• Materials Science
• Inorganic Chemistry
• Chemical Engineering

Background:

• Barium precursors are crucial for YBCO thin film deposition via MOCVD.
• Existing precursors often suffer from polymerization and suboptimal thermal stability.
• Developing stable, volatile barium precursors is essential for efficient thin film growth.

Purpose of the Study:

• To synthesize novel barium complexes with enhanced thermal stability and controlled volatility.
• To investigate the structural and thermal properties of barium complexes coordinated with cyclic ligands.
• To evaluate the suitability of these new precursors for YBCO thin film MOCVD.

Main Methods:

• One-pot alcohol-water synthesis of barium complexes with cyclen, tetraazatetramethyl-12-crown-4, and 1,4,10,13-tetaaoxa-7,16-diazacyclooctadecane ligands.
• Single-crystal X-ray diffraction for structural elucidation.
• Thermogravimetric analysis (TGA) to assess thermal stability and decomposition behavior.
• Density Functional Theory (DFT-D3) calculations for electronic and interaction analysis.

Main Results:

• Successfully synthesized mononuclear/dinuclear barium complexes with enhanced coordination stability.
• Observed suppression of polymerization tendencies due to N/O-coordinated bonds.
• Achieved a significant reduction in initial volatilization temperature (up to 111 °C) and single-stage weight loss.
• Demonstrated improved residual mass at 600 °C, indicating enhanced thermal stability and reduced volatile byproducts.
• DFT-D3 calculations confirmed strong electron-donating capabilities of N atoms and stabilizing van der Waals interactions.

Conclusions:

• Cyclic ligands effectively optimize barium precursor performance for YBCO thin film MOCVD.
• The strategy provides a paradigm for designing metal-organic compounds with tailored thermal stability and volatility.
• Novel barium complexes exhibit superior thermal properties compared to commercial precursors.
• This research facilitates advancements in thin film deposition techniques.