The impact of film thickness and melt-quenched phase on the phase transition characteristics of Ge₂ Sb₂ Te₅

This study investigates the detailed phase transition behavior of Ge 2 Sb2 Te5 (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. © 2010 American Institute of Physics.