Low leakage current characteristics of YMnO3 on Si(111) using an ultrathin buffer layer of silicon oxynitride

We have grown YMnO3 (YMO) thin films on Si(111) using silicon oxynitride (SiON) as a buffer layer. Thickness of SiON buffer layer was well controlled within 2 nm. High resistance of ultrathin SiON layer (d(SiON)similar to0.7 nm) to Si oxidation was confirmed by x-ray photoelectron spectroscopy (XPS). Using the ultrathin SiON layer, we obtained c-axis oriented ferroelectric phase of YMO. Although capacitance-voltage curves of Al/YMO/SiON/Si(111) showed hystereses attributed to ferroelectricity of the YMO films, the memory window was not sufficient (0.2 V), seemingly due to poor crystallinity of the YMO films. On the other hand, leakage current characteristic was good enough for application. The typical value of leakage current density was 10(-8) A/cm(2) at a drive voltage of +/-5 V. In this article, the details of the characterization elucidated by using x-ray diffraction, atomic force microscopy, and XPS will be shown as well. (C) 2000 American Institute of Physics. [S0021-8979(00)03722-1].