Highly textured Pb(Zr0.3Ti0.7)O3 thin films on GaN/sapphire by metalorganic chemical vapor deposition

Highly (111) textured Pb(Zr0.3Ti0.7)O-3 (PZT 30/70) films were deposited on (0001) GaN/sapphire substrates using liquid-source metalorganic chemical vapor deposition (MOCVD) technique at 520 degrees C and 80 nm/min. The crystallinity of as-deposited PZT films and the structure of PZT/GaN interface were evaluated by x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), respectively. Mitigated by geometric epitaxy and strain energy minimization, the orientation relationships of PZT on epi-GaN, determined using x-ray pole figure and selected area diffraction pattern, were as follows: out-of-plane alignment of [111] PZT//[0001] GaN, and orthogonal in-plane alignments of [11 (2) over bar] PZT//[1 (1) over bar 00] GaN (zone axes) and [1 (1) over bar0] PZTH[ 11 (2) over bar0] GaN. The nanochemistry of the PZT (150 nm)/GaN interface, studied using analytical TEM, indicated a chemically sharp interface with interdiffusion limited to a region below 5 nm. The properties of as-deposited PZT on GaN by MOCVD are briefly compared with PZT by sol-gel processing, radio-frequency sputtering, and pulsed laser deposition.