Growth and Characterization of Conducting ZnO Thin Films by Atomic Layer Deposition

ZnO thin films were grown on Si or SiO2/Si substrates, at growth temperatures ranging from 150 to 400 degrees C, by atomic layer deposition (ALD) using diethylzinc and water. Despite the large band gap of 3.3 eV, the ALD ZnO films show high n-type conductivity, i.e. low resistivity in the order of 10(-3) Omega cm. In order to understand the high conductivity of ALD ZnO films, the films were characterized with X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, elastic recoil detection, Rutherford backscattering, Photoluminescence, and Raman spectroscopy. In addition, the various analytical data of the ZnO films were compared with those of ZnO single crystal. According to our analytical data, metallic zinc plays an important role for the high conductivity in ALD ZnO films. Therefore when the metallic zinc was additionally oxidized with ozone by a modified ALD sequence, the resistivity of ZnO films could be adjusted in a range of 3.8 x 10(-3) similar to 19.0 Omega cm depending on the exposure time of ozone.