Effect of oxide structure on the Fermi-level pinning at metal/Gd2O3 interfaces

The extent of Fermi-level pinning at metal/Gd2O3 interfaces is studied as a function of oxide structure by comparing the flatband voltage of Ta- and Pt-gated capacitors. The flatband voltage shift between the two metals, which equals the difference in effective work functions, was found to be largest when the oxide is single crystalline (1.30 +/- 0.05 V), while lower values are measured when the oxide is domain structured (1.05 +/- 0.05 V) or amorphous (0.80 +/- 0.05 V). These results indicate that long-range ordering has a dominant effect on Fermi-level pinning at metal/high-k interfaces.