The Preparation and Properties of Volatile Tris(N-Alkoxycarboxamidato)chromium(III) Complexes as Potential Single-Source Precursors for the MOCVD of Crystalline Chromium Oxide Thin Films

The synthesis, characterization, and vapor-phase growth of volatile Cr(III) complexes as single-source precursors for Cr₂O₃ thin films are reported. A series of Cr complexes─Cr(mdpa)₃ (mdpa = N-methoxy-2,2-dimethylpropanamide) (1), Cr(edpa)₃ (edpa = N-ethoxy-2,2-dimethylpropanamide) (2), Cr(empa)₃ (empa = N-ethoxy-2-methylpropanamide) (3), and Cr(mpa)₃ (mpa = N-methoxypropanamide) (4)─were synthesized via salt elimination reactions between CrCl₃·3THF and N-alkoxy carboxamidate salts. These complexes were characterized by Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis (TGA), single-crystal X-ray diffraction (SC-XRD), Hirshfeld surface analysis, powder X-ray diffraction (PXRD), and vapor pressure measurement. The crystal structure of complex 1 revealed a distorted octahedral geometry with a κ² (O,O) binding mode. TGA demonstrated that complex 1 underwent weight loss at 132 °C and no residue remained at 500 °C. The enthalpy of vaporization of 1 was estimated to be 25.58 kJ/mol, making it an optimal precursor for Cr₂O₃ thin films. The XRD patterns of Cr₂O₃ films deposited on SiO₂/Si substrates confirmed their crystalline nature, showing prominent peaks at 2θ = 33.5° and 41.5°. In addition, X-ray photoelectron spectroscopy validated the target Cr/O ratio, supporting the successful formation of Cr₂O₃ films.