P. Piseri et al., Production and characterization of highly intense and collimated cluster beams by inertial focusing in supersonic expansions, REV SCI INS, 72(5), 2001, pp. 2261-2267
Intense and collimated supersonic cluster beams have been produced by explo
iting inertial focusing effects. To this goal we have developed and tested
a novel focusing nozzle (focuser). Using this device with a pulsed micropla
sma cluster source we have obtained cluster beams with a divergence of 10 m
rad and average densities of 3x10(10) atoms/cm(3) (2x10(12) atoms/cm(3) pul
sed) corresponding to deposition rates of 2 nm/s at 300 mm distance from th
e source nozzle. With a focusing nozzle cluster thermal relaxation and mass
distribution in a supersonic expansion can be controlled. We have measured
the cluster transverse velocities, with extremely high precision, by chara
cterizing the cluster beam deposition on a substrate by an atomic force mic
roscope. Besides the relevance for the understanding of relaxation processe
s in expanding jets, the inertial focusing of clusters has several importan
t consequences for the synthesis of nanostructured films with controlled st
ructure and for all the experimental techniques requiring intense and colli
mated cluster beams. Due to its simplicity the focusing nozzle presented he
re can be used with a wide variety of cluster sources. (C) 2001 American In
stitute of Physics.