Reversible Phase Transformations during In-Situ Heating of Uncapped Ge 2 Sb 2 Te 5 Films

Abstract

Chalcogenides-based phase-change materials (PCMs), especially Ge-Sb-Te compounds, show superior properties for non-volatile electronic memory applications (Wuttig & Yamada, 2007). In operation, the alloy undergoes amorphous-to-crystalline cyclic phase transformations with the thermal energy applied through electrical pulses. In the “Reset” operation, the materials transform from the crystalline phase to the amorphous phase with the application of a short and high amplitude electrical pulse followed by rapid quenching. Whereas, during the “Set” operation, the material transforms to the crystalline phase with the application of a longer and lower amplitude electrical pulse (Friedrich, et al., 2000). These transformations are also associated with the formation of several intermediate structures which can significantly affect their operation. Structural and chemical understanding of these crystallized and recrystallized phases are crucial to design advanced devices with higher capabilities. In-situ heating in TEM (Kooi, et al., 2004) and the subsequent microstructural and microchemical analysis of the nanoscale phase transformation using different TEM techniques is the most viable tool for these analyses (Carter & Williams, 2016; Williams & Carter, 2009).