Temperature-Dependent Local Structural Changes of Amorphous Thin Ge20Te80 Film Revealed by In Situ Resistance, X-Ray Diffraction, and Raman Spectroscopy Studies

Although numerous chalcogenide glass systems including GeTe6 and GexSe100−x have been explored for Ovonic Threshold Switch (OTS) selectors in vertically stackable cross-point memory applications, yet an improved thermal and structural stability at elevated temperatures remains a key challenge. Herein, a systematic temperature-dependent experimental investigation on the thermal stability and local structural changes of as-deposited amorphous thin Ge20Te80 film is conducted for a wide range of temperatures from 25 to 260 °C. The coherent experimental studies reveal that the amorphous phase is stable up to 180 °C, and the crystallization process is initiated above 180 °C, by simultaneous crystallization of Te and GeTe until ≈238 °C as substantiated by temperature-dependent sheet resistance, X-ray diffraction, and Raman spectroscopic measurements. Furthermore, the local structural changes over the crystallization process of Ge20Te80 thin film are elucidated by Raman spectroscopy. These experimental findings provide a decisive understanding of the thermal stability and structural evolution of Ge20Te80 thin films toward designing stable OTS selector materials.