Influence of the PZT film thickness on the structure and electrical properties of the ZnO/PZT heterostructure

In this study, ZnO/PZT films have been continuously deposited on SiO₂/Si substrate using radio frequency reactive magnetron sputtering method. The influence of PZT film thickness on the crystallization, surface microstructure and electrical properties of ZnO films were investigated. The X-ray diffraction results showed that the ZnO/PZT-330-nm-thick films had a perfect c-axis preferred orientation and better crystal structure compared to other samples. Simultaneously, the stress in the films has been shown to change from compressive to tensile with the increase of PZT film thickness. Atomic force microscopy displayed that the microstructures of the ZnO/PZT films with little thickness were loosened, and the grains presented a lamellar structure. However, the ZnO films showed a dense, uniform and crack-free uniform microstructure as increasing the PZT film thickness. The relative dielectric constant and dielectric loss of the ZnO/PZT-330-nm-thick films were approximately 21.7 and 0.52 %, respectively. The leakage current density of the ZnO/PZT films first decreased and then increased with increasing PZT film thickness. The ZnO/PZT-330-nm-thick films had a lowest leakage current density of approximately 10⁻⁶ Acm⁻² at −5 V, which showed excellent insulating characteristic.