Reporting their results in the journal Nanotechnology, researchers at the Institute of Solid State Physics in Bremen and at the Institute of Solid State Physics in Jena, Germany, have demonstrated a very simple and inexpensive way to passivate these defect centres and enhance the UV emission by a factor of almost 50.

The ZnO nanowires were grown using a vapour-liquid-solid (VLS) process and treated by a mild argon plasma at a pressure of 10–1 mbar. Measurements performed by the team of the absolute photoluminescence intensities revealed an almost complete quenching (~97%) of the green luminescence and a giant enhancement (46 times) of the UV emission at room temperature after the treatment.

Further investigations by the group showed that in such an environment the argon plasma produces large amounts of hydrogen ions, which get incorporated into the ZnO crystal. Clear signatures of hydrogen-bound exciton emission were observed in the photoluminescence spectra of the treated samples recorded at low temperature (10 K). Additionally, the team demonstrated that a direct implantation of H2+ or H+ ions produces qualitatively the same results, thus confirming the above interpretation.

The scientists observed that the enhancement in UV emission was stable at room temperature even after one month. This makes the process very promising for the realization of efficient UV emission from ZnO nanowires.