Experimental and computational analysis of ionized
cluster beam deposition
Dave Turner , Howard Shanks
Journal of Applied Physics Vol. 70, No. 10, 5385-5400 (15 November 1991).
Ionized cluster beam (ICB) deposition has received
considerable attention since its introduction in 1972 by Takagi et al.
at Kyoto University because of its potential for low-temperature film
growth. While further investigation of many aspects of ICB deposition
is warranted, it is first necessary to determine with some certainty
whether large clusters are being produced. A complete analysis of the
Eaton ICB source involving computer calculation of the potential fields
and computer simulation of the electrons and ions as they react to and
influence these fields provides an in-depth understanding of the
dynamics that influence the final ion beam characteristics. A high-
resolution time-of-flight mass spectrometer was developed to
experimentally investigate the cluster size distribution. No evidence
of large clusters was found down to a level more than two orders of
magnitude below what the Kyoto University group has reported [T.
Takagi, Ionized-Cluster Beam Deposition and Epitaxy, (Noyes, New
Jersey, 1988)]. A computer analysis of the three Kyoto University
cluster size experiments that form the foundation of ICB has shown that
the potential fields in the ionization areas are critically distorted
by either space-charge effects or design flaws, both of which are
serious enough to invalidate the experiments. The theory behind large
cluster production and the body of indirect evidence attributed to the
presence of large clusters are not convincing by themselves so it is
concluded that a Takagi-type source does not produce large clusters in
quantities capable of affecting film growth.
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