Abstract
A comparative study of the effects of methane and hydrogen as reactive agents on the structural, optical, and electrical properties of ZnO thin films deposited by magnetron sputtering has been performed. The research was aimed at the identification of the nature of the previously reported strong n-type doping effect of methane. To that end, the impact of carbon and hydrogen released by the plasma decomposition of methane on the properties of ZnO films was compared with the impact of molecular hydrogen intentionally added to argon. Both methane and hydrogen caused strong enhancement of n-type conductivity in ZnO films; however, the doping effect of methane was found to be about one order of magnitude larger. The main structural effect of methane was the loss of preferential orientation and a decrease in the size of ZnO crystallites. Room-temperature photoluminescence of these films exhibited a strongly reduced green-yellow emission band in the visible spectral range accompanied by the development of a specific blue emission band. The hydrogen concentration in the ZnO films deposited using methane examined by secondary ion mass spectroscopy was found to be significantly larger than that in the films deposited using pure molecular hydrogen, which is suggested to be one of the reasons for the superior n-type doping efficiency of methane in comparison with molecular hydrogen. The enhanced structural disorder caused by methane is suggested as another contribution to the doping effect of methane.
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Funding
The work was supported by the Ministry of Education and Science of Ukraine in the frame of the joint research programs of Ukraine and Czech Republik (project #M/22-2021), by Fundamental research program (Project #2211-F), by the Program Science for Peace and Security (NATO project SPS G5853). This work was also supported by the Czech Science Foundation (Project No. 20-24366S) and by the Ministry of Industry and Trade of the Czech Republic (Institutional Support Project).
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AR performed technological deposition processing of ZnO films. Spectral ellipsometry measurements and corresponding calculations were performed by SM. Raman scattering measurements were performed y ASN and VS. ANN and IT examined electrical parameters of the samples. Structural parameters from XRD were provided by AG and VK. RY and JG were responsible for SEM and PL measurements while JL and IE performed SIMS experiments. AV was involved in all experiments and was a major contributor in writing the manuscript.
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Vasin, A.V., Rusavsky, A.V., Mamykin, S.V. et al. On the nature of doping effect of methane in ZnO thin films deposited by RF-magnetron sputtering. J Mater Sci: Mater Electron 33, 6421–6431 (2022). https://doi.org/10.1007/s10854-022-07814-9
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DOI: https://doi.org/10.1007/s10854-022-07814-9