Deposition of Fe clusters on Si surfaces

We have used an ultrahigh vacuum scanning tunneling microscope to investiga te the deposition of mesoscopic iron clusters from a gas aggregation source . The size of the clusters was found to be in the range 1-7 nm. The effect of exposure of the iron clusters to the atmosphere results in a significant increase in cluster size, which we believe is consistent with total oxidat ion of the clusters. A specially designed quadrupole mass filter is incorpo rated inside the cluster source. We have investigated the sizes of the clus ters deposited using different quadrupole settings and find that it is poss ible to size select the clusters prior to deposition. Finally we have studi ed the effect of sample surface reactivity and annealing on cluster distrib ution. (C) 2000 American Vacuum Society. [S0734-211X(00)10606-7].