Growth and characterization of electron trapping optical memory materials

Abstract

Electron-trapping optical memory (ETOM) based on infrared-stimulated luminescence (ISL) in phosphor materials can be utilized to store optical information as trapped electrons (write-in) and the information stored can be read out by IR laser beam scanning of the phosphor materials as luminescence. Alkaline-earth-sulfides (AES) such as SrS or CaS codoped with Eu and Sm (abbreviated as SrS:Eu,Sm and CaS:Eu,Sm) have been considered to be good candidates for ETOM materials. On the other hand, AES thin films are difficult to grow due to refractory and hygroscopic nature of the materials. Most of these films reported in the literature are polycrystalline in nature with low degree of ordering. We have successfully grown SrS:Eu,Sm by solid-source molecular-beam-epitaxy technique. We provide direct evidence from our AFM images that different sizes of SrS islands in cubic shape can be achieved under appropriate growth conditions. We have also shown that the ISL can be observed from the films at above room-temperature. A novel idea was also demonstrated that the ISL intensity can be significantly improved by the Zn incorporation into the films. The successful growth of AES would attract crystal growth study, and open wide range of applications such as electroluminescence display devices and a viable route to high speed optical recording at near atomic storage densities.