Electron-beam-induced optical memory effect in metallized ZnO thin films for the application of optical storage

Optical memory effect has been observed in Al- and Mg-capped ZnO thin films. Irradiate a focused electron beam on metallized ZnO films can result in a strong enhancement in band edge emission. Time-dependent cathodoluminescence (CL) reveals that, under electron irradiation, the band edge emission increases dramatically within several minutes without any change in the deep-level emissions. It is also found that, after irradiation, the emission intensity in metallized ZnO increases by almost eight times stronger than that of the bare counterpart. To demonstrate the feasibility of using Al/ZnO and Mg/ZnO films as data storage material, micron-scale optical data array has been fabricated by using a write-read routine. The emission pattern is not self-erasable, and the memory effect is sustainable even after several months without much degradation. As Al forms a good Ohmic metallization on ZnO, they can be used for fabricating high-density optical storage device.