Band offsets in Sc2O3/ZnO heterostructures deposited by RF magnetron sputtering

ZnO is promising for a number of applications in light emission, sensors, and transparent conducting electronics, but its surface is susceptible to instabilities caused by atmospheric exposure. Thus, there is a need for stable passivation or gate dielectric layers that might obviate this issue. One potential candidate is Sc2O3. The authors have measured the band offsets of sputtered Sc2O3 on both Zn-and O-terminated ZnO using x-ray photoelectron spectroscopy and obtained the bandgaps of the materials using reflection electron energy loss spectroscopy. The valence band offset was determined to be similar to 1.67 +/- 0.16 eV for Sc2O3 on Zn-terminated ZnO (bandgap 3.26 eV) and 1.59 +/- 0.16 eV on O-terminated ZnO (bandgap 3.22 eV), i.e., similar within experimental error. The conduction band offset for Sc2O3/ZnO was then determined to be 4.92 eV. The Sc2O3/ZnO system has a staggered, type II alignment, meaning that it is not suitable for thin film transistors but it may still be useful for surface passivation. (C) 2015 American Vacuum Society.