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

Abstract

The coefficient of thermal expansion and biaxial elastic modulus of metastable tetragonal β-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 β phase, and during cooling, after the film had transformed to the stable bcc α phase. While the thermal expansion coefficients of the two phases were similar, β phase films were much more compliant than α films. The thermal expansion coefficient and biaxial elastic modulus of the α phase were consistent with values reported for bulk α tantalum.