STM-ASSISTED MANIPULATION OF AG NANOPARTICLES

We report scanning tunneling microscope (STM) investigations of inert- gas-evaporated Ag nanoparticles deposited on atomically flat, H-termin ated Si(111) surfaces, to which they weakly stick. For the present pur pose, nanoparticles having an average size of 3 nm are fabricated and the particle coverage on the substrate fluctuates between one and thre e monolayers. The weakly coupling particle network can repeatedly be i maged with the STM without inadvertently manipulating the fundamental building blocks. When the STM is operated in the field-emission regime and the tunnel current is kept between 50 pA and 39 mu A, the tempera ture of the nanoparticles rises, thus stimulating local manipulation p rocesses. Depending on the power density dissipated in the particles, we distinguish between a local sintering process leading to the format ion of narrow necks to the nearest neighbors, while the original granu lar nature of the particle layer is maintained, and a complete fusion. In the latter case, stable nanometer-scale structures are fabricated which strongly interconnect with the underlying substrate. In combinin g nanoparticle-inherent properties with existing theory, we roughly es timate the temperature rise of the nanoparticles and confirm the possi bility of particle liquefaction for the highest power densities genera ted.