Structural and electrical properties of metal contacts on n-type ZnO thin film deposited by vacuum coating technique

The authors report on fabrication and characterization of Al and Pt metal contacts on ZnO thin films grown on ITO coated glass substrates using thermal evaporation technique. The structural and surface properties of ZnO thin film were studied by using x-ray diffraction and atomic force microscopy techniques. Atomic force micrographs revealed that ZnO microparticles have perfect pyramidal shape with small surface roughness (average rms value of 3 nm). The current voltage characteristics of Pt/ZnO and Al/ZnO contacts were studied by scanning tunneling microscopy. The Pt contact on ZnO thin films behaves as a rectifying contact with a barrier height of 0.72 eV, while Al contact on ZnO thin film turns out to be Ohmic in nature. The band gap of ZnO thin film was estimated to be 3.10 eV from absorption spectroscopic measurements. (C) 2009 American Vacuum Society. [DOI:10.1116/1.3196786]