In situ backside Raman spectroscopy of zinc oxide nanorods in an atmospheric-pressure dielectric barrier discharge plasma

Abstract

This work presents in situ backside Raman spectroscopy as a method for the investigation of atmospheric-pressure plasma modification of thin oxide films on metals. By using the backside of a permeable electrode, various contributions from the plasma (UV radiation, electrons, etc.) are blocked, which allows us to solely evaluate the effect of the plasma effluent. This approach is applied to study the influence of different gas mixtures (Ar, Ar/H2O, and Ar/O2) on the plasma treatment of zinc oxide nanorod films. The spectral analysis reveals the interaction of the plasma effluent with the zinc sublattice, introducing defects dependent on the plasma gas-phase composition. The in situ measurements show that both the effluent/surface interaction and the resulting defects induce lattice stress in the wurtzite structure. Ex situ Raman measurements demonstrate that the defect stability over time depends on the defect type. The results for the dielectric barrier discharge plasma modification of ZnO-nanostructured thin films indicate that the presented Raman spectroscopic setup is suitable for a variety of systems with a focus on remote plasma modifications.