npj: 相变材料——MoTe2相变材料: 既能马儿快快跑, 又能马儿少吃草

From 知社知社学术圈 2019-03-29

海归学者发起的公益学术平台

分享信息，整合资源

交流学术，偶尔风月

相变材料在热和信息存储方面拥有巨大的应用潜力，因为它们可在外部刺激下于不同物相（和性质）之间切换。然而，在这个转换过程中所散发的热量会限制器件的工作效率和进一步小型化。当相变存储器采用热驱动结构相变时，主流非易失性存储技术虽能做到更低的编程电压和更低的能量耗费，但产生的废热常带来诸多负面影响，制约材料的广泛应用。最近理论预测显示，采用静电驱动结构相变的一些二维材料，存在一种无热机制，有可能改变高能耗状况。来自美国斯坦福大学的一个研究小组，基于密度泛函理论计算模拟了静电驱动的MoTe₂单层相变过程和热驱动的Ge₂Sb₂Te₅薄膜相变过程，发现MoTe₂ 单位体积的热耗散比Ge₂Sb₂Te₅的少100~10000倍。前者不像后者那样会让大部分能量转变成废热，因此可以实现器件的快速运行且耗费更低的能耗——既能马儿快快跑又能马儿少吃草。该文近期发表于npj Computational Materials 4:2 (2018); doi:10.1038/s41524-017-0059-2。

英文标题与摘要如下，点击阅读原文可以自由获取论文PDF。

Theoretical potential for low energy consumption phase change memory utilizing electrostatically-induced structural phase transitions in 2D materials

Daniel A. Rehn, Yao Li, Eric Pop & Evan J. Reed

Abstract Structural phase-change materials are of great importance for applications in information storage devices. Thermally driven structural phase transitions are employed in phase-change memory to achieve lower programming voltages and potentially lower energy consumption than mainstream nonvolatile memory technologies. However, the waste heat generated by such thermal mechanisms is often not optimized, and could present a limiting factor to widespread use. The potential for electrostatically driven structural phase transitions has recently been predicted and subsequently reported in some two-dimensional materials, providing an athermal mechanism to dynamically control properties of these materials in a nonvolatile fashion while achieving potentially lower energy consumption. In this work, we employ DFT-based calculations to make theoretical comparisons of the energy required to drive electrostatically-induced and thermally-induced phase transitions. Determining theoretical limits in monolayer MoTe₂ and thin films of Ge₂Sb₂Te₅, we find that the energy consumption per unit volume of the electrostatically driven phase transition in monolayer MoTe₂ at room temperature is 9% of the adiabatic lower limit of the thermally driven phase transition in Ge₂Sb₂Te₅. Furthermore, experimentally reported phase change energy consumption of Ge₂Sb₂Te₅ is 100–10,000 times larger than the adiabatic lower limit due to waste heat flow out of the material, leaving the possibility for energy consumption in monolayer MoTe₂-based devices to be orders of magnitude smaller than Ge₂Sb₂Te₅-based devices.