Kolobov A V, Fons P, Tominaga J
Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562, Japan.
Sci Rep. 2015 Sep 1;5:13698. doi: 10.1038/srep13698.
Phase-change memories (PCM) are associated with reversible ultra-fast low-energy crystal-to-amorphous switching in GeTe-based alloys co-existing with the high stability of the two phases at ambient temperature, a unique property that has been recently explained by the high fragility of the glass-forming liquid phase, where the activation barrier for crystallisation drastically increases as the temperature decreases from the glass-transition to room temperature. At the same time the atomistic dynamics of the phase-change process and the associated changes in the nature of bonding have remained unknown. In this work we demonstrate that key to this behavior is the formation of transient three-center bonds in the excited state that is enabled due to the presence of lone-pair electrons. Our findings additionally reveal previously ignored fundamental similarities between the mechanisms of reversible photoinduced structural changes in chalcogenide glasses and phase-change alloys and offer new insights into the development of efficient PCM materials.
相变存储器（PCM）与基于GeTe的合金中可逆的超快速低能量晶体到非晶态转换相关联，这两种相在环境温度下具有高稳定性，这一独特特性最近被归因于玻璃形成液相的高脆性，即随着温度从玻璃化转变降至室温，结晶的活化能垒急剧增加。与此同时，相变过程的原子动力学以及相关的键合性质变化仍然未知。在这项工作中，我们证明了这种行为的关键在于由于孤对电子的存在而在激发态形成的瞬态三中心键。我们的发现还揭示了硫族化物玻璃和相变合金中可逆光致结构变化机制之间以前被忽视的基本相似性，并为高效PCM材料的开发提供了新的见解。
