GENERATION, ANALYSIS, AND DEPOSITION OF SILICON NANOCRYSTALS UP TO 10NM IN DIAMETER

Silicon clusters have been generated by CO?laser-induced decomposition of SiH4 in a flow reactor. By introducing a conical nozzle into the r eaction zone, the clusters are extracted into a molecular beam apparat us and analyzed with a time-of-flight mass spectrometer. Besides small clusters, the mass spectra show also very large aggregates containing a few thousand of silicon atoms. A velocity analysis of the neutral c luster beam reveals that the particle velocity decreases with increasi ng mass. Thus it is possible to perform a size selection of the neutra ls by introducing a velocity selector into the cluster beam. The silic on clusters have been deposited at low energy, and TEM micrographs of size-selectively prepared films are presented. A quantitative analysis of two different deposits reveals mean particle diameters of 3.5 and 6.5 nm. The results demonstrate the possibility of fabricating thin fi lms of nanostructured materials with a mean particle diameter controll ed by combining the cluster beam deposition technique with a velocity selector.