Negative-ion implantation into thin SiO2 film on Si and formation of silver nanoparticles in the film

Ag nanoparticles with diameter about 3 nm were formed in center region of 50-nm-thick SiO₂ thin film on Si substrate by silver negative-ion implantation. These metal nanoparticles are expected their application to single electron devices. Silver negative ions were implanted with 30 keV into a 50-nm-thick SiO₂ film on Si with various doses, and with subsequent annealing. Optical reflection properties showed the formation of Ag nanoparticles in the film. The state of nanoparticles in the thin oxide film was observed by a cross-sectional scanning TEM. The sample of 1 × 10¹⁵ ions/cm² showed nanoparticles with diameter of about 2 - 3 nm distributed in the center of the SiO₂ film on Si. The location of nanoparticles was in good agreement with the calculated profile by TRIM-DYN, Various size in 4 - 8 nm in diameter of nanoparticles were formed in samples of 1 × 10¹⁶ and 1 × 10¹⁷ ionS/cm². In the I-V characteristics measured at room temperature for the sample (1 × 10¹⁵ implanted and 700°C annealed), clear steps with voltage width of 0.10 - 0.12 V were observed. These Coulomb blockade voltages correspond to the nanoparticle with diameter of 2 - nm. This result well agreed with The TEM observation.