Studies of local electric properties and annealing behaviors of thin Er2O3 film grown on Ge substrates

In-situ investigations on annealing behaviors of local electric properties of Er2O3 high-κ thin films grown on Ge substrate are realized by conductive atomic force microscopy (CAFM) aided with three-grade marks in size for position relocation. Each island observed in the atomic force microscopy images corresponds to one leaky spot in the corresponding CAFM images, both having a typical size of 100 nm in diameter. The leakage currents at the islands could be reduced at least three orders of magnitude after the sample was annealed in O2 at the temperature of 400 °C. Annealing in N2 at the same temperature had a rather different effect for the leakage currents at the islands, which initially decreased and then increased with annealing time. Annealing in both kinds of ambient for longer periods of time would result in the formation of new leaky islands. Results of scanning Auger electron spectroscopy showed a less oxygen concentration in the islands for the as-grown sample. Combined with results of cross-sectional high-resolution transmission electron microscopy, the possible mechanism for the electric leakage at islands is discussed.