Abstract
The measurement of residual stress on highly textured thin films is usually problematic. When using traditional sin2□ x-ray diffraction method to measure residual stress on textured thin films, the tilt angle □□may have to be limited in a very narrow range to acquire valid data□ which may lead to measurement errors due to too small sampling volume. To solve this problem, we proposed a new x-ray diffraction method, in-plane-sin2□ x-ray diffraction method to measure the residual stress for highly textured thin films. For a fiber textured thin films, the plane orientation is nearly random distributed in the azimuthal direction, which can be used to extend the range of the tilt angle □ in the XRD technique. Our proposed technique employed the synchrotron x-ray source and an eight-circle diffractometer in NSRRC, by the high intensity of x-ray source and slightly shifting the □ and □ angles of the diffractometer to acquire the in-plane diffraction data, sin2□□XRD method could be operated in a wide range of □ from ±30□ to ±90□. The reliability of in-plane-sin2□ method was verified by another established XRD technique, cos2□sin2□ XRD method which is known as a reliable technique to measure residual stress in thin films. For comparison with the in-plane-sin2□ method, the cos2□sin2□ method was performed on a TiN thin film and the stress was measured by these two methods and the stress was also confirmed by laser curvature method. The measurements showed comparable results with R2 values as high as 99%, indicating the reliability of the proposed method was validated. Then cos2□sin2□ method and in-plane-sin2□ method were applied on highly texture BFO thin films. The results indicated that in-plane-sin2□ method can collect valid data in wider range of □ angle and obtain more reliable residual stress values than cos2□sin2□ method. Therefore, it is noted that the reliable stress data and the effectiveness of R2 value should be assured by wide □-range as using XRD techniques.