Room-temperature blue luminescence from ZnO:Er thin films

Abstract

In this paper, room-temperature blue cathodoluminescence from ZnO:Er thin films has been studied using different electron beam currents. The ZnO:Er thin films used in our experiment were prepared by simultaneous evaporation from ZnO and Er sources. The X-ray diffraction spectra showed that the thin films had a strong preferential c-axis (0002) orientation with a hexagonal crystalline structure. The blue light emission at 455 nm originating from the intra-4f shell transition ( 4F 5/2→ 4I 15/2) in Er 3+ ions was observed at room temperature. This is because many Er ions in the ground states resonantly absorb the energy from the emission related to deep-level defects and cathode ray, then fill in the 2H 11/2 state, the non-radiative relaxation rates from the 4F 5/2 state to the 2H 11/2 state are completely suppressed. The non-linear dependence of the cathodoluminescence intensity on the electron beam current showed a blue light emission above the threshold electron beam current ( I th) of 0.6 μA, which was attributed to the phonon bottleneck effect. Furthermore, the near infrared luminescence at 1.54 μm was obtained at room temperature.