Article

# Full-field measurement of nonuniform stresses of thin films at high temperature.

AML, Department of Engineering Mechanics, Tsinghua University, Beijing, China.

Optics Express (Impact Factor: 3.53). 07/2011; 19(14):13201-8. DOI: 10.1364/OE.19.013201 Source: PubMed

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**ABSTRACT:**The Coherent Gradient Sensor (CGS) system has many merits, such as full field, real time, nondestructive, vibration insensitivity, etc., which is developed to measure the curvatures and nonuniform curvatures changes of film-substrate systems in multiple media with different refractive indexes. The general calculation formula for the curvatures in multiple media are obtained. Take the CGS applied in two types of medium as an example, the presented theoretical analysis has been verified by experimental measurements when the specimen is immerged into water or silicone oil. Moreover, the influences of wave length on the measurement error of this system are reported.Optics and Lasers in Engineering 02/2015; 66:92–97. · 1.70 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We report the diffusion and stress coupling effect during oxidation. An analytical model is developed for the stress and diffusion coupling effect based on equilibrium relationship and diffusion equation considering for the stress effect. Compressive stress will generate during the oxidation due to the growth strain. This growth stress can modify the diffusion coefficient; therefore, the oxidation kinetics is also affected. The coupling effect reduces both the oxidation rate and the stress. The proposed model is applied to predict the oxidation evolution for SiC and its consistence with the experimental data demonstrates the theoretical analysis.Journal of the American Ceramic Society 01/2013; 96(1). · 2.43 Impact Factor -
##### Conference Paper: A novel optical method for measuring the thin film stress

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**ABSTRACT:**This paper proposes a thin-film stress measurement system. By applying a constant velocity to the projection grating along the grating plane, a series of sampling points of the sinusoidal wave can be recorded using a CCD camera. The phase distribution of the optimized heterodyne moiré signal can be extracted by the least-squares sine fitting algorithm and then the surface profile of the tested flexible substrate can subsequently be acquired. Using polynomial fitting method to depict the cross-section curve of the substrate, estimating the resultant curvature radii of the uncoated and coated substrates, and substituting these two radii into the corrected Stoney formula, the thin-film stress of the flexible substrate can consequently be obtained. This method features high stability and high resolution due to the introduction of the projection moiré and heterodyne interferometry.International Symposium on Photonics and Optoelectronics (SOPO 2014); 08/2014

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