High pressure photoluminescence properties and structural stability of Eu doped AlN nanowires synthesized via a direct nitridation strategy

High-aspect-ratio Eu doped AlN (AlN:Eu) nanowires (NWs) were synthesized via direct nitridation strategy. The NWs exhibits a strong green emission of the 5d-4f transition under ultraviolet light excitation. Photoluminescence (PL) spectra and synchrotron angle-dispersive X-ray diffraction (ADXRD) for AlN:Eu NWs were performed under hydrostatic pressures up to above 30 GPa. The pressure-induced monotonic red-shift of emission band (d lambda/dP approximate to 5.9 nm GPa(-1)), as well as changes in the emission band widths, have been correlated with pressure for visible-light optical pressure sensors. As the pressure reaches around 20 GPa, the phase transition of AlN:Eu NWs from the wurtzite to rocksalt was found by the appearance of a PL band and ADXRD peak. The enhancement of transition pressure and bulk modulus in AlN:Eu NWs as compared with other ions doped AlN is considered to be caused by co-dopants of Eu2+ and Eu3+ ions. This work provides an effective strategy for doping large-size rare-earth ions into wide band-gap nitride semiconductor, and demonstrates a straightforward pathway for tuning optical properties through pressure without modifying composition. (C) 2020 Elsevier B.V. All rights reserved.