Residual stress analysis of all perovskite oxide cantilevers

Abstract

We have used a method to experimentally determine the curvature of thin film multilayers in all oxide cantilevers. This method is applicable for large deflections and enables the radius of curvature of the beam, at a certain distance from the anchor, to be determined accurately. The deflections of the suspended beams are measured at different distances from the anchor point using SEM images and the expression of the deflection curve is calculated for each cantilever. With this expression it is possible to calculate the value of the radius of curvature at the free end of the cantilever. Together with measured values for the Youngs Modulus, this enabled us to determine the residual stress in each cantilever. This analysis has been applied to Sr RuO 3 /BaTiO 3 /Sr RuO 3 , BaTiO 3 /MgO/SrTiO 3 and BaTiO 3 /SrTiO 3 piezoelectric cantilevers and the results compared to two models in which the stresses are determined by lattice parameter mismatch or differences in thermal expansion coefficient. Our analysis shows that the bending of the beams is mainly due the thermal stress generated

A New Material for High‐Temperature Lead‐Free Actuators

“…Figure a shows characteristic X‐ray diffraction (XRD) traces of three BTO‐SmO films (40, 100 and 500 nm thickness) on (001) SrTiO 3 (STO) substrates measured at room temperature (RT). Consistent with our earlier studies, the out‐of‐plane lattice parameter of the BTO was found (100 nm film in Figure 1a) to be in tension by ≈1% compared to bulk BTO ( c = 0.40593 nm compared to 0.40343 nm in bulk BTO) 7. As we discussed in an earlier report, from measured out‐of‐planes lattice parameters, it was found that 2× (001) BTO‐strained‐comp.…”

“…The strain in the self‐assembled BTO‐SmO composite develops in the vertical direction between the BTO matrix and the ≈10 nm SmO pillars which grow embedded in the matrix. This vertical interfacial strain is caused by lattice mismatch between the two phases in the film, rather than from thermal expansion mismatch (brought about by cooling from the deposition temperature) which could be expected to predominate in thicker (>100 nm) BTO films, which are interfaced with the substrate on one side only 6, 7…”

Controlling Octahedral Rotations in a Perovskite via Strain Doping

“…The coherent growth on STO is expected from many previous studies on the growth of SRO films 17 23 25 . It is worth noting that the measured out-of-plane lattice parameter of 3.952 Å is exactly what is expected of a stoichiometric SRO film fully epitaxially strained on an STO substrate given SRO’s known Poisson ratio of SRO (ʋ = 0.33) 31 . By introducing progressively higher doses of He into the SRO lattice, we observe that the 002 peak shifts to lower angles.…”

Vibration Analysis and Evaluation of Piezoelectric Micromachined Ultrasonic Transducers Using Epitaxial Pb(Zr, Ti)O3 Thin Film

“…Poisson's ratio (−) Pt (10) 21500 171 0.39 SRO (11) 6500 190 0.3 SiN (12) 3100 285 0.2 Polyimide (13) 1420 2.6 0.34 Table 2 Material properties for FEM analysis (2). in air.…”