Charge trapping materials possess intrinsic memory that can be used for optical data storage and processing. However, the low temperature (cryogenic) charge transport and trapping properties are poorly understood. Here, we demonstrate that quantum tunnelling between luminescent donors and intrinsic traps in a photostimulable phosphor enables efficient cryogenic luminescent memory. We establish that BaFCl/Eu is an ideal tunnelling-type phosphor. Charges are transported by optically excited tunnelling between spatially correlated Eu2+ and vacancy centers. Charging is more efficient at ambient temperatures due to the existence of a weak thermal barrier (25 meV). The distribution of correlated centers produced during charging is biased to shorter separations at higher temperatures and the encoded distribution persists as the temperature changes. Then, the discharging efficiency is primarily influenced by the charging conditions. Regardless, the cryogenic suppression is small compared to alternative systems.
Schuyt et al. (Thu,) studied this question.