Multi-technique investigation of Ni-doped ZnO thin films on sapphire by metalorganic chemical vapor deposition

Jiwei Chen, Guangxi University
Jiabin Wang, Guangxi University
Vishal Saravade, Missouri University of Science and Technology
Ian T. Ferguson, Kennesaw State University
Weiguo Hu, Guangxi University
Zhe Chuan Feng, Guangxi University
Lingyu Wan, Guangxi University


Optical and material properties of nickel-doped zinc oxide (ZnO-Ni) grown by metalorganic chemical vapor deposition with varying Ni source flow rates are investigated. ZnO-Ni showed a good crystal quality with (002) orientation but deteriorated at high Ni source flow rates. Photoluminescence responses show a reduction in the bandgap of ZnO-Ni with an increase in the Ni source flow and also with an increase in the temperature. Ni-doping can enhance luminescences at low concentrations (<25 SCCM and>∼2%) and suppress at high concentrations. Ni-related defects occur more toward the surface than bulk of the thin films. Longitudinal optical phonon replicas named 1LO and 2LO redshifts at low Ni source flow rates ≤100 SCCM with an increase in the temperature from 14 to 300 K, but exhibits an "S-shaped"red-blue-red shift with a dip at 50 K at higher Ni source flow rates (150 SCCM). Ni-doping also induces asymmetric crystal vibrations and rougher surfaces with the Ni incorporation. This study enhances the understanding of Ni-doped ZnO that is needed to apply transition-metal doped ZnO for various optoelectronic applications.