Effect of domain boundaries on the electrical properties of crystalline Gd2O3 thin films

We report on the effect of domain boundaries on the electrical properties of epitaxial Gd2O3 thin films grown on Si(001) substrates with 4 degrees miscut along [110] azimuth. Dedicated preparation of the substrate surfaces can lead to two different microstructures of epitaxial Gd2O3 layers when grown at identical growth conditions. A substrate surface with terraces of biatomic steps height is the key point to achieve single crystalline epitaxial Gd2O3 layer. Such epi-Gd2O3 layers exhibited significantly lower leakage currents compared with the commonly obtained epitaxial layers with two orthogonal domains. However, for capacitance equivalent thickness below 1 nm, this difference disappears, indicating that for ultrathin layers direct tunneling becomes dominating. Additionally, forming gas annealing can reduce the leakage current by a few orders of magnitude. Here, thinner layers of both structural types exhibited similar electrical properties.