Practical Considerations for Determining Thin Film Oxygen Surface Exchange Coefficients, Elastic Constants, Thermal Expansion Coefficients, Thermo-Chemically Induced Stresses, and Thermo-Chemically Induced Strains from Wafer Curvature Measurements

Abstract

Wafer curvature measurements have recently been developed as a new, electrode-free method for simultaneously measuring dense or porous thin film chemical oxygen surface exchange coefficients and stress states.1, 2 In addition to being one of today’s cheapest electrode-free oxygen surface exchange coefficient measurement techniques (and the only one presently yielding simultaneous surface exchange coefficient and stress data) these measurements allow for the in situ/in operando determination of thin film elastic constants, thermal expansion coefficients, and chemical expansion coefficients.3 Hence, wafer curvature measurements promise to be an important tool in establishing the links between the mechanical state and electrochemical performance of the materials used in solid state battery, fuel cell, memristor, catalytic reactor, and other solid state ionic devices. This presentation will review the recent progress made in applying wafer curvature measurements to the study of oxygen ion conducting materials. Specifically, the presentation will provide 1) an overview of the fitting equations used to extract the aforementioned thin film materials properties from wafer curvature relaxation experiments, 2) materials case studies highlighting use of the technique, 3) a comparison of the technique’s benefits and limitations compared to alternative approaches, 4) a review of the sample geometric considerations and substrate material properties necessary to obtain reliable data, 5) a detailed description of the experimental setup used at Michigan State to conduct these experiments, 6) a breakdown of the system costs, and 7) a series of practical tips for successful implementation of the technique. Acknowledgements This work was supported by National Science Foundation Award Number CBET-1254453.