The Nanoscale Electrical Damage Mechanism of Ge₂Sb₂Te₅ Phase-Change Films Discovered by Conductive Atomic Force Microscopy

Abstract

We study the nanoscale electrical damage of Ge2Sb2Te5 (GST) phase-change films during crystallization by conductive atomic force microscopy (C-AFM) and Raman spectra. Amorphous GST ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${a}$ </tex-math></inline-formula> -GST) can be converted to crystalline GST ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${c}$ </tex-math></inline-formula> -GST) by applying an exciting direct current (DC) bias (8 V) between the tip and the GST surface. Furthermore, as film thickness increased, the electrical-induced region of GST films revealed a gradual increase in electrical damage and improved crystallinity. It shows that GST films with a thickness of 70 nm have a better crystallization ratio of 20.5 % and less electrical damage with a volume expansion rate of 19.1±6.5%.