Large Local‐Compressive Stress‐Induced Improvements in Piezoelectric Characteristics of Lead Zirconate Titanate Thin Films on a Ni Nanodots Array

Abstract

AbstractInterfacial stress present in ferroelectric thin films is known to affect largely their piezoelectric properties by modifying crystal orientation and domain structure. Here, a nonconventional way is proposed to substantially improve the polarization and piezoelectric characteristics of Pb(Zr,Ti)O3 thin films by modifying the surface of the typical Si substrate into an embossed structure with Ni nanodots. Uniform Ni nanodot arrays are successfully produced by an external magnetic field through the consolidation process of thin Ni layer. The exceptionally large thermal expansion mismatch of ≈94% between the thin films and the Ni nanodots is believed to induce a large local‐compressive stress around the nanodot region and thus the intensified orientation toward c‐axis. For this demonstration, the in situ sputtering processing enabled by combining heavily 12 mol% Nb‐doping with a bottom electrode structure of Ir/TiW is used. As a highlight of the improvement, a significant increase of ≈33% in effective piezoelectric coefficient is observed for the 90 nm Ni nanodot case. An apparent shift of the polarization–electric field curve suggests the existence of internal field, as an evidence of the in situ domain formation.