Ultraviolet light-emitting diodes using MgZnO-coated and bare ZnO nanorod arrays as active layers were manufactured. Both types were exposed to ambient air over a 1-yr period to assess their stability. By monitoring the electroluminescence evolution with air-exposure time and comparing the changes of electroluminescence and x-ray photoelectron spectra before and after vacuum desorption, it is concluded that surface-adsorbed O2 and OH− species, as acceptor and donor surface states, quench ultraviolet electroluminescence, and favor undesirable surface-mediated nonradiative and deep-level recombination. The MgZnO coating prevents surface adsorption, and so the coated nanorod device shows higher efficiency and stability than the uncoated one.

We investigated the electronic reconstruction at the n-type LaAlO3/SrTiO3 interface with hard x-ray photoelectron spectroscopy (HAXPES) under grazing incidence. By exploiting the collapse of evanescent x-ray waves and the abrupt increase of x-ray absorption at the critical incidence angle, our HAXPES study reveals a 2% electronic reconstruction from Ti4+ to Ti3+ occurring near the interface. Such an electronic reconstruction also extends from the interface into SrTiO3 with a depth of about 48 Å (∼12 unit cells) and an estimated total charge transfer of ∼0.24 electrons per two-dimensional unit cell.