A Laser Beam Deflection System for Measuring Stress Variations in Thin Film Electrodes

The bending beam method for measurements of stress in thin films deposited on an elastic substrate in the form of a thin stripe has been improved by the introduction of a laser beam deflection system and of a laser spot position detector. With this improvement, stress measurements have been performed in situ during the electrochemical reactions of palladium hydride formation and of valve metal anodic oxidation. Stress changes in the thin films of 10 7 N/m 2 can be measured with a time response better than 1s. This allows the detection of rapid reactions (like H diffusion in a Pd thin film) and of the electrostriction effect even in anodic films with thickness below 20 nm.