Cold plasma treatment of ZnO:Er nano- and microrods: The effect on luminescence and defects creation

Abstract

The effect of hydrogen and oxygen plasma treatment has been studied in erbium doped zinc oxide (ZnO:Er) nano- and microrods synthesized by the hydrothermal growth. It has been found that hydrogen plasma does not affect the phase purity of the samples whereas the oxygen plasma created the Er2O3 crystalline phase and led to partial powder amorphization only in the ZnO:Er(1%) sample. According to the X-ray photoelectron spectroscopy the modification/improvement of the ZnO surface structure can be expected after the oxygen plasma treatment. The exciton-related luminescence band was improved by the hydrogen plasma treatment whereas the VZn-related red luminescence band was moderated with the dependence on the Er content. The existence of energy transfer between the VZn and Zni was assumed. Correlated experiments of electron paramagnetic resonance and photoluminescence allowed to infer that hydrogen plasma also affects the Er3+ distribution and incorporation into ZnO rods. The red band appeared suppressed after oxygen plasma treatment while the exciton-related emission remained unchanged. The luminescence mechanism was proposed. Shallow donors also appeared affected by the plasma treatment in the low-level Er doped ZnO while the increased Er content seemed to protect them from the plasma influence. Moreover, plasma treatment resulted in the creation of new point defects.