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High-Throughput Investigation of a Lead-Free AlN-Based Piezoelectric Material, (Mg,Hf)xAl1–xN
journal contribution
posted on 2017-05-08, 00:00 authored by Hung H. Nguyen, Hiroyuki Oguchi, Le Van Minh, Hiroki KuwanoWe
conducted a high-throughput investigation of the fundamental
properties of (Mg,Hf)xAl1–xN thin films (0 < x < 0.24)
aiming for developing high-performance AlN-based piezoelectric materials.
For the high-throughput investigation, we prepared composition-gradient
(Mg,Hf)xAl1–xN films grown on a Si(100) substrate at 600 °C by cosputtering
AlN and MgHf targets. To measure the properties of the various compositions
at different positions within a single sample, we used characterization
techniques with spatial resolution. X-ray diffraction (XRD) with a
beam spot diameter of 1.0 mm verified that Mg and Hf had substituted
into the Al sites and caused an elongation of the c-axis of AlN from 5.00 Å for x = 0 to 5.11
Å for x = 0.24. In addition, the uniaxial crystal
orientation and high crystallinity required for piezoelectric materials
to be used as application devices were confirmed. The piezoelectric
response microscope indicated that this c-axis elongation
increased the piezoelectric coefficient almost linearly from 1.48
pm/V for x = 0 to 5.19 pm/V for x = 0.24. The dielectric constants of (Mg,Hf)xAl1–xN were investigated
using parallel plate capacitor structures with ∼0.07 mm2 electrodes and showed a slight increase by substitution.
These results verified that (Mg,Hf)xAl1–xN is a promising material for piezoelectric-based
application devices, especially for vibrational energy harvesters.