Improvement of the electrical properties of YMnO3 thin films in a metal/ferroelectric/Si structure

Highly (0001)-oriented films of YMnO3 were grown on n-type Si(100) substrates by a chemical solution deposition with a modified precursor solution. Spin-coated films were crystallized by rapid thermal annealing at 650 degrees C, and showed improved structural and electrical properties. Capacitance-voltage (C-V measurements at 1 MHz showed a counterclockwise hysteresis, with a memory window of 1.9 V at 9 V, due to ferroelectric polarization, and a dielectric constant of 25. The effects of mobile ionic charge and effective interface charge in the C-V measurements were found to be small by investigating the bias sweep rate dependence and flat-band voltage shift, respectively. The interface trap density near the Si midgap was obtained to be about 1.3x10(11) cm(-2)eV(-1) through conductance measurements. Current-voltage characteristics showed a leakage current density of 16 nA/cm(2) at 3 V. An asymmetric polarization-voltage (P-V) hysteresis curve became symmetric one with a remanent polarization value of 0.1 mu C/cm(2) under He-Ne laser illumination. The depolarization field in the ferroelectric film and charge compensation by the light-generated minority carriers may be responsible for the observed P-V characteristics. The low temperature fabrication of this YMnO3 film showed good structural and electrical properties for application to nonvolatile ferroelectric memory devices.