Atmospheric effects on the thermally induced sintering of nanoparticulate gold films

Abstract

Gold (Au) films were formed by sintering of Au nanoparticles (NPs) under gas flows of air, oxygen (O2), nitrogen (N2), or N2 bubbled through formic acid (FA/N2). The microstructure changes of the Au nanoparticulate films were studied when different atmospheres were applied. The Au film sintered under FA/N2 showed the progressive agglomeration and grain growth with porosity in the film, while the film sintered under N2 had NPs without participating grain growth. A necking between NPs was observed in the film, however, unnecked NPs were still found. The Au film sintered under O2 atmosphere showed the NPs agglomeration with various sizes up to 50 nm. X-ray characteristic peaks of the (111)-preferred orientation were observed in all samples. All samples showed N–H stretching at 3200–3300 cm−1 regardless of sintering atmosphere. Hydrocarbon chains (C–H) at 2850–3000 cm−1 were detected in the film sintered under N2. For the Au film sintered under O2, C–H stretching at 2850–3000 cm−1, C–H deformation at 1350–1470 cm−1, and C–O stretching at 1200–1300 cm−1 were observed. C–O stretching at 1600–1700 cm−1 was observed for the film sintered under FA/N2 atmosphere. The electrical resistance of the film was related with microstructures and organic residual materials left in the film. Even though either porosity or carbon residues were observed in the film, the sintering of NPs in FA/N2 or N2 showed the sheet resistance comparable to that of electroplated one.