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We report the first investigation of a trilayer novel gate dielectric stack of Sc2O3/La2O3/SiOx by Scanning Tunneling Microscopy using bias dependent Constant Current Imaging. Knowledge of band structure allows us to study the electrical property of different layers of the gate stack, namely, polycrystalline La2O3 and amorphous SiOx, independently. Imaging at +3.5V, conduction band of the La2O3 layer is probed revealing a polycrystalline film with grain size of 20 to 30nm. Conduction through high conductivity grain boundaries due to dangling bonds can also be observed in this layer, which lends support to the theory of grain boundary assisted current conduction in MOS structures. Imaging at -4V, valence band of the interfacial SiOx layer is probed and an amorphous-like image of the interfacial layer is obtained. We discuss the significance of these results in the light of ongoing interest to us high-K dielectrics for device miniaturization.
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