Scanning tunneling spectroscopy on ZnO(0001) surfaces : evidence for an inhomogeneous electronic structure

We performed low temperature (77 K) scanning tunneling microscopy (STM) and spectroscopy (STS) on the polar Zn-terminated ZnO(0001) surface [1]. STM and STS data show that the surface electronic structure strongly depends on the local morphology : we observe a narrow bandgap and surface states in the flat regions, and, in the defective surface regions, a wide bandgap without surface states. We also image atomically-resolved $(\sqrt{3} \times \sqrt{3})R30^{\circ}$ reconstructions in small defect-free areas.\\[4pt] [1] J. Dumont et al., Appl. Phys. Lett. 95, 132102 (2009).