Cholula-Díaz Jorge L, Barzola-Quiquia José, Videa Marcelo, Yin Chunhai, Esquinazi Pablo
School of Engineering and Sciences, and Department of Chemistry and Nanotechnology, Tecnologico de Monterrey, Av. Eugenio Garza Sada 2501 Sur, Col. Tecnológico 64849 Monterrey, Nuevo León, Mexico.
Phys Chem Chem Phys. 2017 Sep 13;19(35):23919-23923. doi: 10.1039/c7cp04052k.
Zinc oxide (ZnO) thin films were grown by pulsed layer deposition under an N 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 [112[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 10 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 τ, τ and τ of 0.05, 0.26 and 6.00 min, respectively) than the film grown on the a-plane sapphire substrate (characteristic relaxation times for τ, τ and τ of 0.10, 0.73 and 4.02 min, respectively).
在低压氮气气氛下，通过脉冲层沉积法在α-面和r-面蓝宝石衬底上生长氧化锌（ZnO）薄膜。利用X射线衍射进行的结构研究证实，所有薄膜均为纤锌矿相。α-面和r-面蓝宝石上的ZnO薄膜分别沿[0002]和[112[组合 Macron]0]方向生长。室温光致发光测量表明，对于在r-面蓝宝石衬底上生长的ZnO薄膜，本征点缺陷（间隙锌、氧空位、氧反位和锌空位）的存在比在α-面蓝宝石衬底上生长的样品更为显著。在黑暗和正常光照下，在40至10 Hz的交流频率范围内进行了室温阻抗谱测量。在高于100 kHz的频率下观察到异常的正光电阻效应，我们认为这是由于ZnO薄膜中存在本征缺陷所致。此外，对光学时间响应的分析表明，在r-面蓝宝石衬底上生长的薄膜响应更快（τ、τ和τ的特征弛豫时间分别为0.05、0.26和6.00分钟），比在α-面蓝宝石衬底上生长的薄膜（τ、τ和τ的特征弛豫时间分别为0.10、0.73和4.02分钟）更快。
