Ultrafast Ge-Te bond dynamics in a phase-change superlattice

Abstract

A long-standing question for avant-grade data storage technology concerns the nature of the ultrafast photoinduced phase transformations in the wide class of chalcogenide phase-change materials (PCMs). Overall, a comprehensive understanding of the microstructural evolution and the relevant kinetics mechanisms accompanying the out-of-equilibrium phases is still missing. Here, after overheating a phase-change chalcogenide superlattice by an ultrafast laser pulse, we indirectly track the lattice relaxation by time resolved X-ray absorption spectroscopy (tr-XAS) with a sub-ns time resolution. The novel approach to the tr-XAS experimental results reported in this work provides an atomistic insight of the mechanism that takes place during the cooling process, meanwhile a first-principles model mimicking the microscopic distortions accounts for a straightforward representation of the observed dynamics. Finally, we envisage that our approach can be applied in future studies addressing the role of dynamical structural strain in phase-change materials.

Simultaneously High Thermal Stability and Low Power Based on Ti-Doped Ge2Sb2Te5Thin Films

“…4 Nevertheless, several problems still remain before this material can practically be applied. 5 On the one hand, the high reset (amorphorization) current of GST is a major obstacle to the further scaling-down of PCM and development of high density PCM because of the limited on-current drive capability of selectors such as transistors, bipolar junction transistors, and PN junctions. 6 Besides, the low crystallization temperature (160 • C) and poor data-retention (85 • C) of GST is also susceptible to the issue of thermal cross-talk by the proximity effect, which is particularly true in the case of technology nodes below 32 nm.…”

Characterizing optical phase-change materials with spectroscopic ellipsometry and polarimetry

“…When studying time-resolved PCM crystallization and amorphization there is a limit of the fluence, known as threshold fluence [44], over which the processed spot shows Reflective pixel [38] an irreversible change after the preceding pump pulse, thus, each measurement needs to be performed on a fresh region of sample or the sample has to be moved between single measurements and has to be homogeneous over the investigated area [45]. Non optical methods such as time-resolved X-ray absorption [46,47],…”

“…5 shows a scheme of this technique and recent results of its application to the observation of transient effects in crystalline PCM thin film. A wide range of events happens during light-induced phase transitions of PCM between time scales from 0.1 -100 ps [42][43][44][45][46][47][48][49][50][51][52][53][54] and time-resolved ellipsometry in complement with ultrafast structural methods are ideal tools for probing these dynamics.…”

Study on the Performance of Superlattice-Like Thin Film V2O5/Sb in Phase Change Memory

“…The newly developed superlattice-like (SLL) thin film has shown a great potential in accelerating the phase transition speed, lowering the power consumption and reducing the thermal crosstalk between nearby storage units due to its lower thermal conductivity. 18 Compared with monolayer phase change thin film, SLL structure can combine the phase transition performance of different composite layers to obtain better comprehensive performance. 19 In this text, V 2 O 5 19 (mainly combined by covalent bonds) was chosen as a stabilizer to improve the phase-change performance of pure antimony thin film 17 by means of SLL.…”