Achievement of ten-level optical storage using Ge₂Sb₂Te₅–nAg bi-layer composite structure induced by nanosecond pulsed laser.

This article focuses on the development and characterization of a bi-layer composite structure composed of Ge₂Sb₂Te₅ (GST), a chalcogenide phase change material (C-PCM), and silver nanoparticles (nAg) to enhance multi-level optical data storage. The introduction of nAg alters heat distribution during nanosecond pulsed laser irradiation, enabling the GST layer to achieve ten distinct crystal states with different optical reflectivities, compared to only about three states in pure GST films. Raman spectroscopy revealed that nAg reduces compressive stress and grain size in the GST layer, promoting stable intermediate states beneficial for multi-level storage. An optical irradiation device based on GST–nAg demonstrated approximately a threefold increase in storage density over traditional binary storage, suggesting a promising approach for high-density, multi-level optical data storage using practical nanosecond laser technology.