Phase-controlled deposition of copper sulfide thin films by using single-molecular precursors

Herein, we describe the synthesis and characterization of new ligands, N,N-diethyl-N′-(1-naphthoyl)thiourea (1a) and N,N-dipropyl-N′-(1- naphthoyl)thiourea (1b), and their complexes with copper, bis[N,N-diethyl- N′-(1-naphthoyl)thioureato]Cu^II (2a) and bis[N,N-dipropyl- N′-(1-naphthoyl)thioureato]Cu^II (2b). All four compounds (i.e., 1a, 1b, 2a, and 2b) were characterized by elemental analysis, ¹H NMR and ¹³C NMR spectroscopy, and FTIR spectroscopy. The structures of compounds 1a, 1b, and 2b were determined by single-crystal X-ray diffraction analysis. Thermogravimetric analysis of 2a and 2b showed that both compounds decompose between 190 and 370 °C. Compounds 2a and 2b were then used as single-molecular precursors for the deposition of copper sulfide thin films through aerosol-assisted chemical vapor deposition. The phase and purity of the as-deposited thin films were confirmed by powdered X-ray diffraction, which showed that the as-grown films were composed of the orthorhombic (Cu ₇S₄) phase only. Morphological studies of the as-deposited films were performed by using field-emission scanning electron microscopy. The elemental composition of the thin films was determined by energy-dispersive X-ray spectroscopy.