PHOTOLUMINESCENCE AND RESONANT RAMAN-SPECTRA OF SILICON FILMS PRODUCED BY SIZE-SELECTED CLUSTER BEAM DEPOSITION

Silicon clusters and nanocrystals have been generated by CO2-laser-ind uced decomposition of SiH4 in a flow reactor. By introducing a conical nozzle into the reaction zone, the clusters are extracted into a mole cular-beam machine and analyzed with a time-of-flight mass spectromete r (TOFMS). Since the clusters have a size-dependent velocity, a mechan ical velocity selector is used to further narrow their size distributi on and to select a specific mean size. Employing this technique, silic on clusters with different preselected mean sizes have been deposited at low energy on various substrates. Photoluminescence (PL) and resona nt Raman spectra of the resulting films are presented. The crystallite sizes deduced from the Raman spectra confirm the TOFMS measurements. The PL spectra are shifted with decreasing cluster size to smaller wav elengths. Our results agree very well with theoretical predictions for silicon quantum dots.