Comparative study of local structure for sputter deposited nitrogen doped zinc oxide thin films

Abstract Local structures of nitrogen doped zinc oxide (ZnO:N) thin films fabricated by radio frequency magnetron sputtering was were studied using x-ray absorption spectroscopy. Structural parameters such as c / a ratio, unit cell volume, inter-atomic distance and mean-square displacement were calculated by the fitting extended x-ray absorption fine structure (EXAFS) data measured at Zn K edge to a fully occupied wurtzite structure. Principal component analysis (PCA) was utilized to analyze relationships among variables and to differentiate thin film samples based on their structural profiles. It was found that local environment around Zn atoms changed moderately due to N doping and deposition conditions. In particular, lattice-related parameters were strongly correlated with each other and tended to be uncorrelated with mean-square displacements. Information on the local structure for each ZnO:N sample can be represented in a PCA score plot in which samples could be differentiated by their profiles or deposition methods.