METALLIC NANOPARTICLES FOR COMPACT NANOSTRUCTURE FABRICATION AND OBSERVATION OF SINGLE-ELECTRON PHENOMENA AT ROOM-TEMPERATURE

Metallic nanoparticles having a diameter of 2-4 nm are fabricated by i nert gas evaporation techniques and subsequently deposited on an atomi cally stepped, H-terminated Si(111) substrate, to which they stick by means of a weak coupling force. By varying the exposure time of the pa rticle beam to the substrate, the coverage density can be well control led. A scanning tunneling microscope (STM) operated at room temperatur e and under high-vacuum conditions is used to identify, characterize, and deliberately manipulate the nanoparticles. Spectroscopic data of i ndividual particles are compared with that obtained from a pair arrang ement. In the latter case, the mutual interaction gives rise to charac teristic features which we associate with single-electron phenomena. T he weak particle/substrate coupling force allows to displace selected particles to predetermined locations on the substrate surface. Under c onditions of high power densities provided by the electron flow emanat ing from the tip, a local fusion process of a small number of nanopart icles sets in, resulting in the fabrication of compact nanostructures. Particles that do not take part in the fusion process can completely be removed with the STM tip, uncovering the atomic step-terrace patter n of the Si surface. Finally, the expected temperature rise of the nan oparticles under conditions of electron beam irradiation is roughly es timated. (C) 1998 Elsevier Science Ltd. All rights reserved.