Low-energy ion beam treatment of alpha-Al2O3(0001) and improvement of photoluminescence of ZnO thin films

Abstract

A low energy N-2(+) ion beam impinged on a alpha-Al2O3(0001) single crystal surface in the range of fluence 5x10(15)/cm(2)-1x10(18)/cm(2) at room temperature. After ion bombardment, chemical bonding on the modified sapphire surface was investigated by x-ray photoelectron spectroscopy. Below a fluence of 1x10(16)/cm(2), only a non-bonded N1s peak at the binding energy 398.7 eV was found, but further irradiation up to 2x10(11)/cm(2) induced Al-O-N bonding at around 403 eV The occurrence of Al-N bonding was identified at ion fluence higher than 5x10(17)/cm(2) at 396.6 eV II-VI ZnO thin films were grown on an untreated/ion-beam-induced sapphire surface by pulsed laser deposition (PLD) for the investigation of the modified-substrate effect on photoluminescence. The ZnO films grown on modified sapphire containing Al-O-N bording only, and both Al-O-N and Al-N bonding showed a significant reduction of the peak related to deep-level defects in photoluminescence. These results are explained in terms of the formation of Al-N and Al-O-N layers and relaxation of the interfacial strain between Al2O3 and ZnO.