메모리 응용을 위한 PZT 강유전체 박막의 제작과 특성에 관한 연구

초록

We have established the process conditions of the sol-gel deposition method to obtain the high quality of PZT thin films. We have also studied the effects of the Zr/Ti ratio and the bottom electrode (Pt or ITO) on the electrical properties fo the films. Their permittivities and tangent losses with the variation of frequencies were measured by the LCR meter and theri maximum polarizations, remanent polarizations, and coercive fields were obtained from the hysteresis loops measured by the Sawyer-Tower circuit. For the PZT thin film of the Zr/Ti ratio of 53/47, permittivity at 10kHz, coercive field, maximum and remanent polarizations were 952, 20.7kV/cm, 10.43μC/cm2 and 4.3μC/cm2, respectively. For the film of the Zr/Ti ratio of 25/75, coercive field, maximum and remanent polarizations were 33.12kV/cm, 5.59μC/cm2, and 1.5μC/cm2, respectively. For the film of the Zr/Ti ratio of 75/25, coercive field, maximum and remanent polarizations were 23.8kV/cm, 7.45μC/cm2, and 3.5μC/cm2, respectively. Our investigation into the effects of the lower electrode on the electrical properties of PZT films showed the following results. The permittivities of the PZT films deposited on the ITO electrode decrease more quickly than those of the PZT films on the Pt electrode. The tangent losses of the former films increase more quickly than those of the latter. These may be due to the degradation of the quality of the interface between the electrode and the film, which results from diffusion of Pb. It is also noticeable that permittivities and tangent losses of the PZT films deposited on the ITO electrode vary differently with the Zr/Ti ratio. This may indicate that the quality of the interfaces between the electrical that the quality of the interface between the electrode and the film changes with the Zr/Ti ratio of the PZT film.