New Volatile Perfluorinated Amidine-Carboxylate Copper(II) Complexes as Promising Precursors in CVD and FEBID Methods

In the present study, we have synthesised and characterised newly copper(II) complexes with the general formula [Cu₂(NH₂(NH=)CC₂F₅)₂(µ-O₂CR_F)₄], where R_F = CF₃, C₂F₅, C₃F₇, C₄F₉. Infrared spectroscopy, mass spectrometry with electron ionisation (EI MS), and density-functional theory (DFT) calculations were used to confirm compounds' composition and structure. The volatility of the compounds was studied using thermal analysis (TGA), EI MS mass spectrometry, variable temperature infrared spectroscopy (VT IR), and sublimation experiments. Research has revealed that these compounds are the source of metal carriers in the gas phase. The thermal decomposition mechanism over reduced pressure was proposed. TGA studies demonstrated that copper transfer to the gaseous phase occurs even at atmospheric pressure. Two selected complexes [Cu₂(NH₂(NH=)CC₂F₅)₂(µ-O₂CC₂F₅)₄] and [Cu₂(NH₂(NH=)CC₂F₅)₂(µ-O₂CC₃F₇)₄] were successful used as chemical vapour deposition precursors. Copper films were deposited with an evaporation temperature of 393 K and 453 K, respectively, and a decomposition temperature in the range of 573-633 K without the use of hydrogen. The microscopic observations made to investigate the interaction of the [Cu₂(NH₂(NH=)CC₂F₅)₂(µ-O₂CC₂F₅)₄] with the electron beam showed that the ligands are completely lost under transmission electron microscopy analysis conditions (200 keV), and the final product is copper(II) fluoride. In contrast, the beam energy in scanning electron microscopy (20 keV) was insufficient to break all coordination bonds. It was shown that the Cu-O bond is more sensitive to the electron beam than the Cu-N bond.