Determination of the polarity of ZnO thin films by electron energy-loss spectroscopy

The polarity of the ZnO film grown on sapphire using an ultra-thin Ga wetting layer has been investigated by electron energy-loss spectroscopy (EELS). The intensity of the oxygen K-edge in electron energy-loss spectrum from the ZnO film shows a prominent difference when the film orientation changes from the (0002) Bragg condition to the (0002-bar) Bragg condition. The EELS study reveals that the ZnO film with very thin Ga wetting layer has the [0001] polarity, which is further confirmed by the conventional convergent beam electron diffraction method