Electrical properties of ferroelectric PZT sol-gel films

Moscow State Institute of Radioengineering, Electronics and Automation (Technical University), 78, Vernadsky Ave, 117454 Moscow, Russia

There are displayed some new results of experimental and theoretical investigation of sol-gel PZT ceramic thin films at oxidated silicon substrates with Pt electrodes. The solutions for films deposition were prepared by usual techniques from metal alkoxides precursors and by anodic dissolution of metals in methoxyethanol. Both methods result in preparation of thin PZT films with fairly good ferroelectric properties: for 0.1-0.2 mkm films the coercive voltage was 3-5 V, the remanent polarization was more than 10 mkC/cm² with the switching time less than 50 ns.

The main goal of our research was discrimination of and revealing different components of the polarization switching. There were used the Sawyer-Tower circuit for measuring the hysteresis properties over the frequency range of 1-10⁴ Hz, capacitance-voltage techniques at the frequencies 10³-10⁶ Hz, and some modifications of Merz techniques. These lines of approaches have enabled to reconstruct hysteresis loop and to analyze it with respect to film polycrystalinity. The contributions of slow processes of ions migration and electrically active traps at the crystal boundaries were displayed. A connection of observing effects with the phenomena of fatigue and aging was demonstrated. A consideration of metal-ferroelectric interface as a Schottky barrier permits to create a model adequate to experimental data. An analysis of ferroelectric-semiconductor structures in view of surface states due to polarization fluctuation was performed as well.