The impact of film thickness and melt-quenched phase on the phase transition characteristics of Ge2Sb2Te5

Abstract

This study investigates the detailed phase transition behavior of Ge2Sb2Te5 (GST) thin films in the thickness range between 4–30 nm using a static laser tester. It was found that the crystallization time has a minimum for both as-deposited (around 12 nm) and melt-quenched (around 10 nm) amorphous materials. Capping the GST with a thin SiO2 layer changes this behavior and leads to a monotonic increase in crystallization time with film thickness for as-deposited amorphous samples but a decrease in time for melt-quenched, amorphous samples. The shortest crystallization time of about 7 ns was observed for the melt-quenched, amorphous 6 nm thick film. It was also found that the recrystallization time of melt-quenched, amorphous GST was shorter when the melt-quenched area was surrounded by GST in the hexagonal phase compared to GST in the rocksalt phase. The shorter recrystallization times for thinner, capped GST films indicate a promising scaling behavior of these materials for rewritable optical storage and phase change memory.