RECENT DEVELOPMENTS IN IONIZED CLUSTER BEAM THIN-FILM DEPOSITION

Thin film deposition from beams of atomic clusters, some of which are ionized and accelerated to the growing surface, was first proposed in 1972 but suffered from controversy over cluster formation conditions d uring the 1980s. Development of suitable cluster sources has been diff icult and large clusters of zinc (about 2000 atoms per cluster) have o nly recently been produced in the 1990s. The conditions for cluster sy nthesis without using a carrier gas presently require a high vapor pre ssure, 1000 Torr or more, thus severely limiting the materials from wh ich cluster beams can be formed. Our results now suggest that the nozz le is serving as the heat sink for the heat of condensation of the zin c clusters. Effects of further intentional cooling of the nozzle on zi nc cluster distributions are reported. An additional problem is the de velopment of suitable real-time cluster measurement methods. Two diffe rent methods using simultaneous beam velocity and energy analysis are presented. One method is based on mechanical beam chopping and the oth er on electrostatic beam chopping.