A simple oleylamine-based thermal decomposition process using different time steps for precursor injection was used to obtain bimetallic Ag−Cu nanoparticles with a narrow size distribution. Experimental and theoretical studies were carried out to demonstrate that these bimetallic nanoparticles are less prone to oxidation. The calculated energy trends for O 2 adsorption on the nanoparticles show that the adsorption energy declines rapidly when more than six O 2 molecules are present, indicating that O 2 is rarely adsorbed on Ag−Cu nanoparticles. Electron transfer from Cu to Ag within these bimetallic nanoparticles allows far better resistance to oxidation than monometallic Cu nanoparticles.

To fabricate a low cost, highly conductive ink for inkjet printing, we synthesized a gram scale of uniformly sized Sn nanoparticles by using a modified polyol process and observed a significant size-dependent melting temperature depression from 234.1 °C for bulk Sn to 177.3 °C for 11.3 nm Sn nanoparticles. A 20 wt% of Sn nanoparticles was dispersed in the 50% ethylene glycol: 50% isopropyl alcohol mixed solvent for the appropriate viscosity (11.6 cP) and surface tension (32 dyn cm(-1)). To improve the electrical property, we applied the surface treatments of hydrogen reduction and plasma ashing. The two treatments had the effect of diminishing the sheet resistance from 1 kΩ/sq to 50 Ω/sq. In addition, conductive patterns (1 cm × 1 cm) were successfully drawn on the Si wafer using an inkjet printing instrument with conductive Sn ink. The maximum resistivity for an hour of sintering at 250 °C was 64.27 µΩ cm, which is six times higher than the bulk Sn resistivity (10.1 µΩ cm).

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Acetic acid (AA) has been employed to reduce the surface capping ligands of Ag nanoparticles (NPs) for the fabrication of low-temperature-processable and highly conductive Ag ink. The ligand reduction of the Ag NPs was achieved using a one-step method, in which oleylamine (OA)-capped Ag NPs were immersed in AA for different durations (1, 2, 3, 5 and 10 h). The weight of the total capping ligand was reduced from 12.1 wt% to 2.3 wt% by 10 h AA immersion. According to in situ transmission electron microscopy (TEM) and electrical resistivity, the ligand-reduced Ag NPs were cured at a much lower temperature (approximately 100 C) and showed better electrical performance than OA-capped NPs under the same conditions. To investigate the reason for this enhancement of the electrical properties, we characterized the surface chemistry of the Ag NPs by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), which revealed that the surface capping ligand was exchanged from the OA to the acetate ion. In addition, the adsorption energy of the ligand was increased by the ligand exchange, which was studied using density functional theory (DFT) calculations. DFT was effective in explaining the adsorption of each ligand on Ag NPs and indicated that the ligand can be exchanged by AA immersion.

Various-sized Ag nanoparticles capped with oleylamine were synthesized by means of a thermal decomposition process for low-temperature electronic devices. The Ag nanoparticles, which had diameter of 5.1 nm to 12.2 nm, were synthesized in incubation and ripening stages related to nucleation and growth. After the Ag nanoparticles were made into ink with a proper solvent, inkjet printing and thermal sintering methods were used to form a metal thin film with thickness of 100 nm. A type of thermal sintering related to percolation transformation and surface sintering was conducted at a temperature much lower than the melting point of bulk Ag. The electrical resistivity was examined with the aid of a four-point probe system and compared with the resistivity of bulk Ag, showing that the Ag film had much higher resistivity than bulk Ag. To improve the electrical stability and properties, we applied hexamethyldisilazane (HMDS) surface treatment to the substrate and dipped the as-deposited films into methanol. Both treatments helped to diminish and stabilize the resistivity of the printed conductive films.

For enhanced wetting properties of Zn-doped solder alloys, this paper proposes Cu 5 Zn 8 -bearing solders. A mechanical alloying process with controlled milling time and rotational speed was used to successfully fabricate Cu 5 Zn 8 -bearing powders with a diameter of 50 lm to 70 lm. Their composition was identified by inductively coupled plasma atomic emission spectroscopy. After the powders were made into a paste with a rosin-activated type of flux, the wetting angles of the Cu 5 Zn 8 -bearing paste solders on a Cu substrate were compared with the wetting angles of bulk solder alloys with the same amount of Cu and Zn alloying elements. The reason for the enhanced wetting properties of Cu 5 Zn 8 -bearing solders is explained by thermodynamic calculations and differential scanning calorimetry experiments. In addition, the interfacial reactions and the shear strength with Cu substrates are also discussed.

To control the optical properties of Cu 2 O for a variety of application, we synthesized Cu 2 O in nanoscale without other treatments. Cu 2 O nanoparticles with an average size of 2.7 nm ( ≤ 3 7%) were successfully synthesized in this study via a modified thermal decomposition process. Copper (II) acetylacetonate was used as a precursor, and oleylamine was used as a solvent, a surfactant and a reducing agent. The oleylamine-mediated synthesis allowed for the preparation of Cu 2 O nanoparticles with a narrower size distribution, and the nanoparticles were synthesized in the presence of a borane tert-butylamine (BTB) complex, where BTB was a strong co-reducing agent together with oleylamine. UV-vis spectroscopy analysis suggest that band gap energy of these Cu 2 O particles is enlarged from 2.1 eV in the bulk to 3.1 eV in the 2.7-nm nanoparticles, which is larger than most other reported value of Cu 2 O nanoparticles. Therefore, these nanoparticles could be used as a transparent material because of transformed optical property.