Selective Purcell enhancement of defect emission in ZnO thin films

A zinc interstitial defect present but unobservable in ZnO thin films annealed at 500 °C in oxygen or in atmosphere was selectively detected by interaction of the film with an Ag surface-plasmon polariton. The time-dependent differential reflectivity of the ZnO near the ZnO/MgO interface exhibited a subpicosecond decay followed by a several nanosecond recovery, consistent with the Purcell-enhanced Zn interstitial luminescence seen in Ag–ZnO heterostructures. Heterostructures annealed at other temperatures showed significantly greater band-edge photoluminescence and no evidence of the Zn interstitial defect.