Solubility of bis-(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) in mixed supercritical CO2 and H2 systems for application in supercritical fluid deposition of Cu

• Solubility of Cu(tmhd)2 in pure supercritical CO2 system and binary mixtures of scCO2 and H2 was measured.
• H2 was found to have negative impact on the solubility.
• Framework to predict the solubility in the binary system was constructed via correlation of experimental results.
• Guideline for constructing optimal feed system of Cu(tmhd)2 was settled for supercritical fluid deposition of Cu.
• The addition of O2 and N2 into scCO2 also have negative impact on the solubility.

We measured the solubility of bis-(2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (Cu(tmhd)2) in pure supercritical CO2 (scCO2) and binary mixtures of H2 and scCO2 at 40–100 °C and 11–20 MPa using spectrometric method. The solubility in scCO2 was dependent on the density of CO2. The addition of H2 to the scCO2 had negative impact on the solubility, and the solubility was proportional to density of CO2 with a constant mole fraction of H2. The equations proposed by Mendez-Santiago and Teja as well as Sauceau et al. were able to correlate the solubility in the pure CO2 and binary systems. This approach provides a framework to determine the precursor concentration for supercritical fluid deposition (SCFD) of Cu. The precursor feed system for optimal Cu-SCFD was discussed. In addition, the same effect was found with the addition of O2 and N2 into scCO2, suggesting that further investigation into the solubility of SCFD precursors in these binary systems is warranted.

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