Formation and size control of a Ni cluster by plasma gas condensation

We have constructed a plasma-gas-condensation type cluster deposition appar atus and tried to find the optimum operation conditions for controlling the cluster site. Transmission election microscope (TEM) observation has been done to evaluate sizes of Ni clusters produced when varying the volume of a cluster growth region, sputtering power, and inert gas pressure. The mean cluster size decreases by decreasing the volume of growth region and the sp uttering power. The smallest cluster obtained in this work is about 2.3 nm in diameter. We have considered the following two models for the cluster gr owth: (1) a cluster-cluster collision growth and (2) an atomic vapor conden sation growth. The cluster growth speed estimated from the former is too sl ow, while that from the latter is reasonable in comparison with the present experiments. When stable embryos are made from atom collisions, they grow up faster and the final cluster sizes estimated from the latter model are c onsistent with those observed by TEM. (C) 1998 American Institute of Physic s. [S0021-8979(98)01321-8].