### Session X40: Focus Session: Morphology and Evolution at Surfaces: Defects and Transport

8:00 AM–10:12 AM, Friday, March 25, 2005
LACC Room: 408A

Chair: Katsuyo Thornton, University of Michigan

Abstract ID: BAPS.2005.MAR.X40.9

### Abstract: X40.00009 : The Structure, Stability and Origin of beta-Phase Ta

9:36 AM–9:48 AM

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#### Authors:

Aiqin Jiang
Trevor Tyson
Lisa Axe
(New Jersey Institute of Technology)

Tantalum thin films exhibit two crystalline phases, bcc ($\alpha$-phase, the bulk structure of tantalum) and metastable tetragonal $\beta$-phase, which differ in both mechanical and electrical properties. In order to understand the stability of the $\beta$ phase and the origin of the $\beta$-to-$\alpha$ phase transformation, molecular dynamics simulations have been performed on tantalum clusters. Molecular dynamics simulations show that the $\beta$ phase is stable with a very high melting point. No phase transformation was observed for pure $\beta$-Ta clusters from room temperature to the melting point. Simulations of Ta clusters with mixed $\alpha$ and $\beta$ phases revealed that inclusion of a small $\alpha$-Ta cluster inside a $\beta$-Ta cluster induces $\beta$ to bcc transformation at a temperature far below its melting point, depending on the cluster size and $\alpha$ to $\beta$ atom ratio. These results suggest that the observed $\beta$ to bcc transformation results from the presence of small $\alpha$-phase grains within the $\beta$-Ta films. The growth of $\beta$-Ta on substrate as a result of strain is being evaluated.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.MAR.X40.9