An apparatus for the measurement of internal stress and thermal expansion coefficient of metal oxide films

Abstract

A measuring apparatus based on a phase shifting interferometry technique to determine the mechanical properties of metal oxide films was presented. Thin films were prepared by ion-beam sputter deposition at low substrate temperature. Quantitative determination of the mechanical properties such as the internal stress, biaxial elastic modulus, and thermal expansion coefficient of metal oxide films were investigated. A phase shifting Twyman–Green interferometer with the phase reduction algorithm was setup to measure the temperature-dependent stress in thin films. Two types of circular glass plates, with known Young’s moduli, Poisson’s ratios, and thermal expansion coefficients, were used as coating substrate. The temperature-dependent stress behavior of the metal oxide films was obtained by heating samples in the range from room temperature to 70 °C. The stresses of thin films deposited on two different substrates were plotted against the stress measurement temperature, showing a linear dependence. Four oxide films were reported for their film stresses and thermal expansion coefficients.

A new method for the determination of the coefficient of thermal expansion of solid materials

“…Standard methods include mechanical dilatometry [1], laser interferometry [2] and high magnification optical imaging [3]. The increasing use of computer-based thermo-mechanical models as well as specific requirements concerning anisotropic materials has determined in the last few years a greater need for quantitative data, promoting the development of new full-field optical measurement techniques, such as those based on Electronic Speckle Pattern Interferometry (ESPI) [4][5], phase-shifting interferometry [6] and digital image correlation [7]. All these techniques differs from each other only for the way the material expansion is measured with, since the reference temperature is always determined by monitoring the air temperature inside the heating device used to exert thermal loading, rather than measuring it directly on the sample surface.…”

Stress development of direct-patternable PZT film for applying to micro-detecting system

“…This result was agreed well with the P-E result because C-V property has important relation with film surface condition and the interfacial defects between film and Pt electrode. The interfacial defects could be also formed by thermal stress developed during film-formation procedure and act as electron trap according to the field direction [15][16].…”

Biaxial stresses, surface roughness and microstructure in evaporated TiO2 films with different deposition geometries

“…3 shows a schematic diagram of the stress measuring apparatus. The phase shift interferometry (PSI) method used for the measurement of stresses in films has been described in a previous publication [10]. The stress distribution is considered anisotropic with respect to x and y, i.e., s x 6 ¼ s y .…”