Variation in mechanical properties with substrate temperature of SbTi thin film deposited by RF sputtering technique

Abstract

Nanoindentation technique has been used to determine the mechanical properties of bismuth layered structure ferroelectric thin films, which have been shown to be promising for MEMS based devices used in sensing, actuation and energy harvesting, especially at elevated temperatures. SBTi (SrBi4Ti4O15) is a promising layered ferroelectric material and thin films of this composition are deposited on amorphous fused silica substrates by rf sputtering technique varying the substrate temperature from 600-725°C. The crystal structure and surface morphology of SBTi thin films are characterized by X-ray diffraction and atomic force microscopy. Depth- sensing nanoindentation system is used to measure the mechanical characteristics of SBTi thin films. Nanoindentation measurements reveal that the Young's modulus and hardness of SBTi thin films are related with grain size and crystal orientation which in turn depend on substrate temperature. The increase in mechanical properties with grain size is observed, indicating the reverse Hall-Petch effect. Furthermore, hardness and Young's modulus of the (119) oriented films were higher than those of (0010) oriented films. The tribological properties of these films are confirmed by performing the scratch tests on the same films. © 2014 VBRI press.