Selective deposition of p-type Cu2O or conductive Cu thin film at 180∘C in air on a quartz glass substrate: Development of an aqueous spray solution using two-compartment electrolysis system

A conductive Cu thin film with a thickness of 170[Formula: see text]nm, electrical resistivity of 8.9(2) [Formula: see text][Formula: see text]cm and adhesion strength of 12(7) MPa was fabricated at 180∘C in air. The spray solutions were prepared by electrolyzing Cu electrodes in an aqueous solution of ammonium formate, and then by adding ethylenediamine-N, N, N[Formula: see text], N[Formula: see text]-tetraacetic acid (EDTA). The surface morphology image of resultant Cu thin film, observed by a field emission scanning electron microscope, revealed Cu grains with particle sizes of ca. [Formula: see text][Formula: see text]nm. It was indicated that the Cu complex containing EDTA ligand in the spray solution plays important roles to (1) provide enough amount of carbon atoms as a reducing agent for phase transition of its coordinated Cu[Formula: see text] to crystalline Cu0 and (2) prevent the product from oxidation under atmospheric O2 during spray coating.