A simple synthesis of Ag2+x Se nanoparticles and their thin films for electronic device applications

A simple method to synthesize silver selenide nanoparticles has been proposed. By changing the ratio of Se-oleylamine complex and silver acetate in the reacting mixture at different temperatures, both size and stoichiometry of the silver selenide particles could be successfully controlled. The size of the nanoparticles was adjusted by changing reaction temperatures. The synthesized silver selenide nanoparticles showed size changes from 3 to 10 nm when the corresponding reaction temperatures were 40–100°C, respectively. In addition to the size change, the stoichiometry of the synthesized nanoparticles (Ag2+x Se) could be adjusted by simply varying the ratio of Ag to Se precursors. Through XPS analyses the x value in Ag2+x Se was determined, and it changed between 0.54 and −0.03 by varying Ag/Se ratio from 2/0.75 to 2/4. The optical property of the nonstoichiometric Ag2+x Se nanoparticles was different from that of stoichiometric Ag2Se nanoparticles, but showed the plasmon absorption of Ag-Ag network. The plasmon absorption was decreased with the increased concentration of the Se precursor. Finally, the Ag2+x Se thin film in this work showed large magnetoresistance and successfully applied to prepare high-performance Schottky diode. The Ag2.06Se film exhibited the magnetoresistance effect up to 0.9% at only 0.8 T at room temperature. The voltage drop and breakdown voltage of the Schottky diode were 0.5 V and 9.3 V, respectively.