Study of zinc thin films formed using large clusters in the ionized cluster beam deposition technique

Abstract

Ionized cluster beam (ICB) deposition uses a beam of ionized, accelerated atom clusters to grow thin films. It has been shown that in ICB efforts prior to late 1991, significant numbers of large clusters were not present in depositing beams. Since that time, formation of such large clusters of zinc by homogeneous nucleation has been demonstrated by Gspann using radiation crucible heating and pulsed ionizer time of flight cluster size measurement and in our laboratory using electron bombardment heating and deflected deposition cluster measurement. Crucible pressure was increased from 2 to over 1000 Torr and a converging–diverging nozzle 18 mm long and 0.4 mm in diameter at the throat was used in place of the older 1 mm×1 mm nozzles. Increasing source pressure from 2.8 to 11.3 atm (280–1130 kPa) is accompanied by an increase in peak average cluster size from a few hundred to over 2000 atoms/cluster. Surface roughness of cluster formed films increases with increasing incident cluster energy using a cluster beam peaking at ∼2200 atoms/cluster in average size for cluster energies from thermal to approximately thermal plus 700 eV.