AVS 60th International Symposium and Exhibition
    Applied Surface Science Thursday Sessions
       Session AS+BI+EM+NL+NS+SS-ThM

Paper AS+BI+EM+NL+NS+SS-ThM12
Influence of Carrier Gas on the Nucleation and Growth of Nb Nanoclusters Formed Through Plasma Gas Condensation

Thursday, October 31, 2013, 11:40 am, Room 204

Session: Nanoparticle Surface Chemistry
Presenter: K.R. Bray, UES, Inc.
Authors: K.R. Bray, UES, Inc.
C.Q. Jiao, UES, Inc.
J.N. DeCerbo, Air Force Research Laboratory
Correspondent: Click to Email
The synthesis and characterization of metallic nanoclusters is a growing field of research due to their promising catalytic, electrical, magnetic, mechanical, and optical properties. These properties generally differ from the bulk material and can be tuned by varying the nanocluster size. Transition metal clusters have received considerable interest due to their wide range of applications. Niobium has attracted attention due to observations of ferroelectric properties at low temperature. In this work, Nb nanoclusters are deposited using a plasma gas condensation process which involves the sputtering of a Nb target to create a dense metallic vapor where clusters are formed. The concept of a temperature dependent nucleation zone in conjunction with classical nucleation theory is used to describe nanocluster nucleation and growth. Changes in the nanocluster nucleation and growth are influenced through modifications of the process parameters such as carrier gas flow rate, sputter source ion current, and aggregation length. Initial data show a novel dual peak cluster distribution under select process conditions, with the smaller cluster diameter near 1 nm and the larger cluster diameter varying from 4 to 10 nm. The larger cluster appears to be a simple condensation product while data suggest the smaller cluster may be a structured cluster with a different nucleation and growth mechanism. The effects of differing argon and helium carrier gas ratios on cluster formation in conjunction with varying sputter source currents and aggregation lengths will be discussed. These results provide the opportunity for a broader understanding into the nucleation and growth of nanoclusters as well as insights into how process parameters interact during deposition. This knowledge will enhance the ability to create nanoclusters with desired size dispersions.