The piezoelectric response of the PZT thin film was investigated for two different crystalline orientations (PZT(110) and PZT(100)) by increasing the applied voltage from 0 V to +9 V,
then decreasing it to −9 V and raising it back to 0 V (i.e. E ranging from −140 to +140 kV/cm) in steps of 0.5 V.
At each step, 30 diffraction patterns with an exposure time of 20 s each were recorded.
Before increasing the voltage to the following step, the voltage was reduced to 0 V for 200 s in order to minimize a possible heating by the Joule effect as described before.
From the change of the 2θ position of the center of the respective Bragg peak at 0 V and at the applied potential, the strain induced by the piezoelectric effects was calculated
. Fig. 3(a) and (b) displays the 2θ profiles for the PZT 110 and 100 reflections, respectively,
recorded at U = 0 V and U = 9 V. Based on those findings, strain profiles for the PZT (110) and the PZT (100) were calculated
Fig. 3(c) displays the piezoelectric strain for the two PZT reflections as a function of the applied voltage,
revealing “butterfly loops” [32]
. These loops are a clear signature for a piezoelectric hysteresis in the thin film.
The piezoelectric effect is a factor of ~2 stronger for grains oriented with [100] out-of-plane direction than for grains oriented with [110] out-of-plane direction,
evidencing piezoelectric anisotropy.
Considering a linear voltage drop over the entire film thickness of 710 nm, the piezoelectric coefficient in the lab reference frame dperp at U = 9 V for the PZT (100)
and PZT (110) yields ~230 and ~110 pm/V,
respectively. These values are in good agreement with theoretical piezoelectric coefficients found in literature for these two crystalline orientations [33,34].
The piezoelectric response of the PZT thin film was investigated for two different crystalline orientations (PZT(110) and PZT(100)) by increasing the applied voltage from 0 V to +9 V,then decreasing it to −9 V and raising it back to 0 V (i.e. E ranging from −140 to +140 kV/cm) in steps of 0.5 V. At each step, 30 diffraction patterns with an exposure time of 20 s each were recorded. Before increasing the voltage to the following step, the voltage was reduced to 0 V for 200 s in order to minimize a possible heating by the Joule effect as described before. From the change of the 2θ position of the center of the respective Bragg peak at 0 V and at the applied potential, the strain induced by the piezoelectric effects was calculated. Fig. 3(a) and (b) displays the 2θ profiles for the PZT 110 and 100 reflections, respectively, recorded at U = 0 V and U = 9 V. Based on those findings, strain profiles for the PZT (110) and the PZT (100) were calculated Fig. 3(c) displays the piezoelectric strain for the two PZT reflections as a function of the applied voltage, revealing “butterfly loops” [32]. These loops are a clear signature for a piezoelectric hysteresis in the thin film. The piezoelectric effect is a factor of ~2 stronger for grains oriented with [100] out-of-plane direction than for grains oriented with [110] out-of-plane direction, evidencing piezoelectric anisotropy. Considering a linear voltage drop over the entire film thickness of 710 nm, the piezoelectric coefficient in the lab reference frame dperp at U = 9 V for the PZT (100) and PZT (110) yields ~230 and ~110 pm/V, respectively. These values are in good agreement with theoretical piezoelectric coefficients found in literature for these two crystalline orientations [33,34].
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