Thermodynamic Characterization of Ruthenium β-Diketonate Complex Ru(thd)3 as a Precursor for the CVD Preparation of Coatings

The thermodynamic properties of ruthenium complex compound Ru(thd)3, (thd is tris(2,2,6,6-tetramethyl-3,5-heptadionate), Ru(C11H19O2)3 have been studied. Temperatures (434.8 ± 2.0, 452.2 ± 1.0, and 461.1 ± 1.0, and 487.8 ± 1 K) and thermodynamic parameters (enthalpy change ΔH = 13.3 ± 2.0, 2.1 ± 0.5, 6.0 ± 2.0, and 3.8 ± 1 kJ mol–1) of three reversible solid-phase transitions and the melting process have been determined by differential scanning calorimetry. The temperature dependence of the saturated vapor pressure in the range 392–488 K has been established by the flow method. The thermodynamic parameters of sublimation (enthalpy change ΔH = 121 ± 1, 103 ± 3, 101 ± 5, and 86 ± 2 kJ mol–1; entropy change ΔS° = 219 ± 3, 176 ± 7, 173 ± 10, 141 ± 4 J mol–1 K–1) for all four crystalline phases have been calculated. CVD diagrams have been calculated by thermodynamic modeling to determine the equilibrium phase composition of the system. The obtained results allow us to give recommendations on finding the optimal conditions for the CVD process and choosing the precursor.