شبيه سازي ميدان فاز استحاله فازي كريستال-آمورف آلياژ GST با در نظر گرفتن اثرات مكانيك و جريان ترموالكتريك

Phase-change materials, particularly chalcogenide alloys, are utilized in various applications, including thermal, electrical, an‎d optical technologies, due to their unique properties. An example is the ternary GST alloy (a combination of germanium, antimony, an‎d tellurium), which has emerged as one of the primary elements in the fabrication of phase-change memories. The distinctive feature of this alloy is its ability to rapidly an‎d reversibly switch its structure from crystalline to amorphous an‎d vice versa, which has attracted significant attention from researchers. In this study, the phase-field model, as an innovative approach, along with mechanical effects such as pressure an‎d elastic an‎d inelastic stresses, has been employed to analyze the phase-change behavior an‎d amorphization of GST. In this research, the free energy in phase-field models for this alloy, in addition to primary terms such as the double-well an‎d thermal terms, also incorporates mechanical effects an‎d strains generated during the transformation process, leading to substantial improvements in simulation accuracy, voltage application methods, an‎d understan‎ding of amorphization an‎d crystallization phenomena. Furthermore, to examine the thermoelectric effects resulting from voltage application on the GST nanolayer, heat conduction an‎d Poisson equations are used for modeling thermoelectric influences, in addition to the phase-field an‎d elasticity equations. Using this method, the patterns of temperature variations an‎d, consequently, crystalline transformations an‎d amorphization in response to voltage have been precisely analyzed, an‎d the critical voltage for the crystallization phenomenon has been determined for various thicknesses of 10, 25, 50, 75, an‎d 100 nanometers, as well as electrical pulse durations of 10, 25, 50, 80, an‎d 100 nanoseconds. The critical voltage is defined as the voltage above which the sample temperature exceeds the melting point, resulting in reverse transformation. Among the key results, the extraction of critical voltage variations with respect to pulse duration can be highlighted, which exhibits an inverse trend for each thickness. Additionally, for a fixed pulse duration, the variations in critical voltage with respect to thickness have been derived, indicating a linear increasing relationship between critical voltage an‎d thickness, where the rate of change in critical voltage with respect to thickness decreases nonlinearly as pulse duration increases. Variations in the distribution fields of phase, temperature, voltage, an‎d stress for different thicknesses have been extracted an‎d compared. It was also determined that the crystal growth rate is independent of thickness an‎d dependent on pulse duration. A mesh study based on four important parameters—maximum stress, crystal volume percentage, interface thickness, an‎d maximum temperature—has been conducted to obtain mesh-independent results. Moreover, the crystal-amorphous phase interface profile has been validated against analytical results. This novel approach, by integrating the phase-field model an‎d accounting for mechanical an‎d thermoelectric effects, can lead to a deeper understan‎ding of the behavior of phase-change alloys an‎d foster significant advancements in the development of new technologies.

مهدي جوان بخت

صالح اكبرزاده , محمد سيلاني