Coefficient of thermal expansion and biaxial elastic modulus of β phase tantalum thin films

The coefficient of thermal expansion and biaxial elastic modulus of metastable tetragonal beta-tantalum thin films were determined from the thermoelastic slopes of films deposited on (100) silicon and fused silica substrates. Measurements were made during heating, when the film was in the beta phase, and during cooling, after the film had transformed to the stable bcc alpha phase. While the thermal expansion coefficients of the two phases were similar, beta phase films were much more compliant than alpha films. The thermal expansion coefficient and biaxial elastic modulus of the alpha phase were consistent with values reported for bulk alpha tantalum. (c) 2007 American Institute of Physics.