Tuning of structural and dielectric properties of Gd_2O_3 grown on Si(001)

摘要

The structural and dielectric properties of gadolinium oxide (Gd_2O_3) grown on Si(001) depending on the epitaxial growth conditions were investigated. Gd_2O_3 layers were grown at temperatures between 250°C and 400°C with an oxygen partial pressure between 2 × 10~(-7) mbar and 5 × 10~(-7) mbar. The crystal structure of the Gd_2O_3 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 Gd_2O_3 on top, as confirmed by TEM. The value of around 33 was extracted for the dielectric constant of monoclinic Gd_2O_3, which is much higher than for cubic Gd_2O_3. The best Gd_2O_3 layers grown at 400°C and pO_2 = 5 × 10~(-7) mbar exhibit also a characteristic leakage current value J(V_(fb) -1V) for a CET value of around 2 nm in the range of a few nA/cm~2, which enable the applicability in electronic devices.