Tuning of structural and dielectric properties of Gd2O3 grown on Si(001)

Abstract

The structural and dielectric properties of gadolinium oxide (Gd2O3) grown on Si(001) depending on the epitaxial growth conditions were investigated. Gd2O3 layers were grown at temperatures between 250°C and 400°C with an oxygen partial pressure between 2×10−7mbar and 5×10−7mbar. The crystal structure of the Gd2O3 turns out to be monoclinic with rotational domains as revealed by x-ray diffraction measurements and transmission electron microscopy (TEM) investigations. The dielectric properties can be tuned with growth temperature, forming gas annealing, and an increase in oxygen partial pressure. Furthermore, the dielectric constant was found to increase with the layer thickness. This can be interpreted in terms of the presence of a two layer stack consisting an interfacial quasi-amorphous and monoclinic Gd2O3 on top, as confirmed by TEM. The value of around 33 was extracted for the dielectric constant of monoclinic Gd2O3, which is much higher than for cubic Gd2O3. The best Gd2O3 layers grown at 400°C and pO2=5×10−7mbar exhibit also a characteristic leakage current value J(Vfb−1V) for a CET value of around 2 nm in the range of a few nA/cm2, which enable the applicability in electronic devices.