Observation of a (√3 × √3)R30° reconstruction on O-polar ZnO surfaces

Low energy electron diffraction shows a (√3 × √3)R30° reconstruction on O-polar ZnO surfaces after a tube furnace annealing process commonly used to create atomic-height steps. This reconstruction is also produced in situ under conditions having an extremely low hydrogen background. X-ray photoelectron spectroscopy suggests H stabilizes the (1 × 1) termination that has been extensively reported. The (√3 × √3)R30° reconstruction is stable against H2, N2, and air, although its formation is suppressed when preparation occurs under a H2 background. Therefore, caution must be taken when using annealed O-polar ZnO substrates, as reconstruction will affect the nature of the surface and, thus, the growth interface.