Surface Chemistry of Copper Nanoparticles and Direct Spray Printing of Hybrid Particle/Metallorganic Inks

Copper films have been direct written on heated substrates using both neat metallorganic and two-component, copper nanoparticle/copper metallorganic inks. Commercial nanoparticle copper (nano-Cu) was characterized by transmission electron microscopy and powder X-ray diffraction (PXRD) and found to consist of spherical particles measuring 100-500 nm in diam. The was etched away using an excess of hexafluoroacetylacetone (Hhfa) and vinyltrimethylsilane (VTMS) yielding pure Cu by PXRD. Hhfa etching in the absence of VTMS led to the formation of millimeter-sized Cu particles at room temperature. Neat (hexafluoroacetylacetonato)Cu(I)-(VTMS) (Cu(hfa)⋅VTMS) was spray printed in a nitrogen ambient on glass microscope slides and Kapton at 210-230°C to give dense, adherent films. Hhfa/VTMS-etched nano-Cu was mixed with (Cu(hfa)⋅VTMS) and spray printed in a nitrogen ambient on glass microscope slides and Kapton at 210-220°C. Copper films produced by both approaches were characterized by scanning electron microscopy and standard four-probe resistivity techniques.