Multidimensional Analysis of Cobalt-Doped Copper Oxide Thin Films Based on Magnetron Sputtering with LIBS
Objective With the rapid advancement of research in nanomaterials,many functional oxide nanofilms have been widely used in various fields.CuO films are low-cost,excellent thin film materials.Elemental doping is possible because of the presence of Cu vacancies in the structure.Co-doped CuO films are prepared by doping Co in CuO thin films.Radio frequency(RF)magnetron sputtering,a method for preparing thin-film materials,has been widely used in scientific research and industrial fields because of its stability and high film-forming quality.However,during the preparation of Co-doped CuO film materials,changes in the magnetron sputtering parameters often lead to differences in the composition ratio,resulting in different sample performances.Therefore,it is necessary to analyze the composition ratio of prepared Co-doped CuO films to analyze the performance of the samples and optimize the process parameters for magnetron sputtering.For this purpose,an existing effective analytical method is used to perform a multidimensional analysis of the composition ratio for the prepared Co-doped CuO films by RF magnetron sputtering at different sputtering parameters.Methods Co-doped CuO films are prepared by magnetron sputtering under different sputtering pressures and powers.The composition ratios of the samples are influenced by sputtering pressure and power,as listed in Table 1.In this study,a multidimensional analysis of Co-doped CuO films is conducted using laser-induced breakdown spectroscopy(LIBS),including quantitative analysis of the element atomic number fraction ratio,two-dimensional mapping of the LIBS intensity ratios of Co/Cu in the films,and optical performance evaluation of the films.Results and Discussions The LIBS experimental setup(Fig.1)and the corresponding LIBS spectra of the Co-doped CuO films(Fig.2)are shown.Plotted calibration curves of the Co/Cu content ratios in the films under different sputtering pressures and powers show that the linear fitting coefficient exceeds 0.99.This indicates good consistency between the LIBS intensity ratio and the element atomic number fraction ratios in the films.In addition,a rapid quantitative analysis of the element atomic number fraction ratio in the film is realized(Fig.3).Based on the two-dimensional mapping of the LIBS intensity ratios of Co/Cu in the films(Fig.4),the Co/Cu intensity ratio first increases with increasing sputtering pressure,then decreases,and subsequently increases.The intensity ratio decreases with an increase in sputtering power,but the distribution uniformity of Co/Cu in the films worsens.In the transmittance spectral analysis of the films(Fig.5),the bandgap of the film reaches a high value at a sputtering pressure of 3.0 Pa and a sputtering power of 75 W.In addition,the evolution laws of the optical bandgaps of the films and the LIBS intensity ratios of Co/Cu are consistent with the sputtering parameters(Fig.6),which provide technical support for the optical performance evaluation of the films.Conclusions In this study,LIBS technology is used to analyze the atomic number fraction ratios of Co/Cu in Co-doped CuO films prepared by magnetron sputtering.The calibration curves of Co/Cu in Co-doped CuO films are plotted using the LIBS intensity ratios and their energy dispersive spectrometry(EDS)values;the linear fitting coefficients are as high as 0.99,indicating rapid qualitative and quantitative analysis of doped elements in CuO films.Two-dimensional distribution mapping of the LIBS intensity ratios of Co/Cu in films is valuable for optimizing magnetron sputtering parameters.By analyzing the transmission spectral evolution of Co-doped CuO films with different sputtering parameters and the corresponding optical bandgap evolution of CuO films with different sputtering parameters,the evolution of the LIBS spectral line intensity ratios of Co/Cu is found to be consistent with the evolution of the optical bandgap of the corresponding CuO films.Based on the Co/Cu atomic number fraction ratios in Co-doped CuO films,the optical properties of CuO films using LIBS are evaluated.The results show the potential of LIBS technology for the multidimensional analysis of Co-doped CuO films,laying a foundation for the analysis of other thin films.
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