“…Owing to the slow decay component of τ 2 , the weak afterglow features can still be viewed for more than 10 min after the removal of the 254 nm UV irradiation source. To the best of our knowledge, such PL features in unintentionally doped AlN has not been reported previously. − To further probe the origin of the long afterglow feature, a 365 nm irradiation source was used to irradiate the as-prepared AlN helices for 2 min in dark room. However, only a weak purple color was observed (Figure j), and no fingerprint of afterglow feature was found after the removal of the 365 nm excitation source (Figure k), which excludes the possible contribution of 430 nm PL emission for the observed afterglow effect.…”