Change in polarity of zinc oxide films grown on sapphire substrates without insertion of any buffer layer

We have investigated the polarity of zinc oxide (ZnO) and Al-doped ZnO films grown oil (11 (2) over bar0) and (0001) sapphire Substrates. using coaxial impact collision ion scattering spectroscopy. The films grown by pulsed laser deposition with it nominally undoped ZnO ceramic target had a (000 (1) over bar) Surface, whereas the films prepared with a 1 mol% Al-doped ZnO ceramic target had a (0001) surface. The usage of Al-doped and undoped targets Caused no difference in the in-plane lattice orientation. Electron microscope observations revealed that polarity change Clue to doping Occurred Without the formation of any interfacial phase between ZnO and sapphire.