Measurements of Piezoelectric Coefficient of Pulsed-DC Sputtered AlN Thin Films by Piezoresponse Force Microscopy

Pulsed-DC reactive sputtering was employed to make fully (0002)-textured AlN thin films with different full widths at half maximum (FWHMs) of (0002) rocking curve. The piezoelectric coefficient d33 was quantitatively measured by piezoresponse force microscopy (PFM). The obtained values were rationalized with the consideration of an enhancement factor due to the strongly localized electric field under the tip, indicating that this approach can be used reliably for d33 measurement. We found that d33 decreases with increasing FWHM. In addition, the piezoresponse amplitude is almost constant from grain to grain, except along the grain boundaries.