Determination of the yield properties of thin films using enhanced coherent gradient sensing

This paper describes coherent gradient sensing (CGS) as an optical, full-field, real-time, nonintrusive, noncontact technique for measurement of curvature and curvature changes in single-layered and multilayered thin films deposited on substrates. The sensitivity of the basic CGS technique is enhanced using optical fringe multiplication to map curvature in very flat specimens (kappa less than or equal to 0.001 m(-1)). Subsequently, this curvature measurement technique is applied to the determination of the yield properties of thin films subjected to cyclic thermomechanical loading.