A conductive nanoink was prepared using copper nanoparticles (CNPs). In order to prevent the oxidation of CNPs, the particles were coated by 1-octanethiol using Vaporized Self-Assembled Multi-layers (VSAMs) method. The coating of 1-octanethiol onto CNPs was confirmed by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Dispersion stability of CNPs was checked by monitoring its viscosity over 6 weeks. The sheet-type of patterned samples using the fabricated ink was sintered at 350 and 230°C, respectively. Electrical resistivity was measured to be 5.69 © 10 ¹8 ³·m when sintered at 350°C and 7.67 © 10 ¹8 ³·m when sintered at 230°C. These results were 3.4 and 4.6 times than the value for bulk copper. During the sintering process, the optimum temperature of removing organic materials was found to be 200°C. This removal temperature dramatically influenced necking and the density of samples. Therefore, 1-octanethiol VSAMs and 1-octanol ink were used successfully for the low-temperature sintering process to fabricate conductive Cu patterns by finding the optimum temperature of 200°C for complete removal of organic materials prior to the sintering process.

Pulsed-wire evaporation (PWE) was used to synthesize copper nanoparticles having an average diameter of about 100 nm. These were coated with 1-octanethiol (CH 3 (CH 2 ) 7 SH) under high vacuum (HV) (5.33 © 10 ¹4 Pa) using vapor self-assembled multilayers (SAMs) to prevent oxidation of the nanoparticles. Conductive nanoink made from the coated nanoparticles was printed on glass. The printed patterns were sintered in hydrogen (99.999 vol%) and mixed gas (Ar 95 vol% + H 2 5 vol%) atmospheres; a high copper line density was achieved. Differential scanning calorimetry (DSC) established that the removal temperature of 1-octanethiol was 143°C, well below the 350°C sintering temperature. Complete removal of 1-octanethiol after sintering was confirmed by X-ray photoelectron spectroscopy (XPS). The resistivity of the hydrogensintered copper sample was 1.74 © 10 ¹7 ³·m. This dry powder fabrication and coating method is an alternative approach to inhibit copper oxidation and form inkjet-printed lines.

No abstract

Oxidation preventive Cu nano ink was prepared using a vapor self-assembed multi-layer coating method (VSAMs). These particles were prepared using 100 nm Cu nano particles coated with 1-octanethiol under ultrahigh vacuum condition with octanol used as a solvent. Octanol-based non-oxidized 10% (wt.) nano ink was well-dispersed without any surfactant. The conductive ink had good dispersion and remains stable for more than 6 weeks. It also has a low viscosity rating of 8.3 cPs. In addition, 5 µL of copper nano ink was dropped into a 1 cm × 1 cm glass substrate to form a copper pattern. The copper pattern was then sintered at 350°C in a tube furnace in a H 2 gas atmosphere. The resistivity of the film using the fabricated ink was determined to be 5.8 × 10 −6 Ωcm. The results show that the non-oxidized oxidation-preventive copper nano ink is suitable for ink-jet printing.

No abstract