Gold and zinc thin films deposited by the ionized cluster beam technique

Abstract

Thin film deposition from beams of atom clusters, some of which are ionized and accelerated to the growing surface, was first proposed in 1972. This idea created interest because it was fundamentally different from other deposition methods and was expected to have unique capabilities. Development of a suitable cluster source has been difficult, and large clusters of zinc (about 2000 atoms per cluster) have only recently been produced. Two source parameters were change to accomplish this. The crucible pressure was increased from 2 Torr 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 nozzle with dimensions of 1 mm × 1 mm. To separate the pressure and nozzle effects, gold thin films are being deposited with the new converging-diverging nozzle. The vapor pressure of gold is much lower than that of zinc at a given temperature. Cluster size measurements show no significant numbers of gold clusters. The effect of the crucible pressure on the formation of the large cluster is much more significant than that of the nozzle geometry. The effects of varying ion energy bombardment on film microstructure are also evaluated using atomic force microscopy.