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Issue 35, 2017
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The frequency-dependent AC photoresistance behavior of ZnO thin films grown on different sapphire substrates

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Abstract

Zinc oxide (ZnO) thin films were grown by pulsed layer deposition under an N2 atmosphere at low pressures on a- and r-plane sapphire substrates. Structural studies using X-ray diffraction confirmed that all films had a wurtzite phase. ZnO thin films on a- and r-plane sapphire have grown with orientations along the [0002] and [11[2 with combining macron]0] directions, respectively. Room temperature photoluminescence measurements indicate that the presence of native point defects (interstitial zinc, oxygen vacancies, oxygen antisites and zinc vacancies) is more preponderant for ZnO thin films grown on the r-plane sapphire substrate than the sample grown on the a-plane sapphire substrate. Room temperature impedance spectroscopy measurements were performed in an alternating current frequency range from 40 to 105 Hz in the dark and under normal light. An unusual positive photoresistance effect is observed at frequencies above 100 kHz, which we suggest to be due to intrinsic defects present in the ZnO thin films. Furthermore, an analysis of the optical time response revealed that the film grown on the r-plane sapphire substrate responds faster (characteristic relaxation times for τ1, τ2 and τ3 of 0.05, 0.26 and 6.00 min, respectively) than the film grown on the a-plane sapphire substrate (characteristic relaxation times for τ1, τ2 and τ3 of 0.10, 0.73 and 4.02 min, respectively).

Graphical abstract: The frequency-dependent AC photoresistance behavior of ZnO thin films grown on different sapphire substrates

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Publication details

The article was received on 16 Jun 2017, accepted on 17 Aug 2017 and first published on 17 Aug 2017


Article type: Communication
DOI: 10.1039/C7CP04052K
Citation: Phys. Chem. Chem. Phys., 2017,19, 23919-23923
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    The frequency-dependent AC photoresistance behavior of ZnO thin films grown on different sapphire substrates

    J. L. Cholula-Díaz, J. Barzola-Quiquia, M. Videa, C. Yin and P. Esquinazi, Phys. Chem. Chem. Phys., 2017, 19, 23919
    DOI: 10.1039/C7CP04052K

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