Non-polar single crystal ZnO (1 0 (1) over bar 0) substrates with hydrogen peroxide (H2O2) treatment were characterized and applied to Schottky barrier diodes. Formation of a ZnO2 layer with a polycrystalline structure was confirmed by 20 scans of X-ray diffraction (XRD) measurements. Tails of the X-ray rocking curve of ZnO (1 0 (1) over bar 0) planes were broadened with increase in H2O2 treatment time. Grain structures were clearly observed on the surfaces of ZnO (1 0 (1) over bar 0) substrates with H2O2 treatment by an atomic force microscope, and the root mean square roughness of the ZnO2 surface was about 5 nm. The current density-voltage (J-V) characteristics of Pd/ZnO/A1 structures using ZnO (1 0 (1) over bar 0) substrates without H2O2 treatment were ohmic. The J-V characteristics of Pd/ZnO2/ZnO/Al structures using ZnO (1 0 (1) over bar 0) substrates with H2O2 treatment time of 5 min showed good rectifying characteristics. The ideality factor n of this diode was 1.7 and the barrier height between Pd films and the ZnO2 layer on the ZnO (1 0 (1) over bar 0) plane was estimated to be 0.92 eV. (C) 2013 Elsevier B.V. All rights reserved.