The determining role of stacking fault in the mechanoluminescence properties of ZnS: Mn thin films

Abstract

As a classical mechanoluminescence (ML) material, the ML behaviors of the doped-ZnS have been studied extensively, but the exact mechanism is still under debate. To address this problem, ZnS: Mn thin films with and without zinc blende ZnS (zb-ZnS) stacking faults on the surface were obtained though tuning growth times. XRD results show that small amount of zb-ZnS is introduced to the wurtzite ZnS (wz-ZnS) by means of annealing process. The 75-min grown film has a bright ML emission centered at 585 nm while the 45-min film is free of ML, but the XRD and XPS analyses show no significant difference in the phase composition of two samples. TEM results show that the 75-min film has a high density of zb-ZnS stacking faults on the surface while the 45-min film is free of stacking faults. Considering the friction-force is applied on the surface, it is reasonable to conclude that the stacking fault is the key for ML emission. Moreover, a model is proposed and well explains the phenomenon that the threshold of ZnS: Mn ML has a wide range rather than a single value. This study helps the understanding of ML mechanism and provides a new strategy to improve the ML efficiency.