Behrens Mario, Lotnyk Andriy, Bryja Hagen, Gerlach Jürgen W, Rauschenbach Bernd
Department of Precision Surfaces, Leibniz Institute of Surface Engineering (IOM), Permoserstr 15, 04318 Leipzig, Germany.
Laboratory of Infrared Materials and Devices, The Research Institute of Advanced Technologies, Ningbo University, Ningbo 315211, China.
Materials (Basel). 2020 May 1;13(9):2082. doi: 10.3390/ma13092082.
Ge-Sb-Te-based phase change memory alloys have recently attracted a lot of attention due to their promising applications in the fields of photonics, non-volatile data storage, and neuromorphic computing. Of particular interest is the understanding of the structural changes and underlying mechanisms induced by short optical pulses. This work reports on structural changes induced by single nanosecond UV laser pulses in amorphous and epitaxial GeSbTe (GST) thin films. The phase changes within the thin films are studied by a combined approach using X-ray diffraction and transmission electron microscopy. The results reveal different phase transitions such as crystalline-to-amorphous phase changes, interface assisted crystallization of the cubic GST phase and structural transformations within crystalline phases. In particular, it is found that crystalline interfaces serve as crystallization templates for epitaxial formation of metastable cubic GST phase upon phase transitions. By varying the laser fluence, GST thin films consisting of multiple phases and different amorphous to crystalline volume ratios can be achieved in this approach, offering a possibility of multilevel data storage and realization of memory devices with very low resistance drift. In addition, this work demonstrates amorphization and crystallization of GST thin films by using only one UV laser with one single pulse duration and one wavelength. Overall, the presented results offer new perspectives on switching pathways in Ge-Sb-Te-based materials and show the potential of epitaxial Ge-Sb-Te thin films for applications in advanced phase change memory concepts.
基于Ge-Sb-Te的相变存储合金最近因其在光子学、非易失性数据存储和神经形态计算领域的应用前景而备受关注。特别令人感兴趣的是对短光脉冲引起的结构变化及其潜在机制的理解。这项工作报道了单纳秒紫外激光脉冲在非晶和外延GeSbTe（GST）薄膜中引起的结构变化。通过结合使用X射线衍射和透射电子显微镜的方法研究了薄膜内的相变。结果揭示了不同的相变，如晶态到非晶态的相变、立方GST相的界面辅助结晶以及晶相内的结构转变。特别地，发现晶态界面在相变时作为亚稳立方GST相外延形成的结晶模板。通过改变激光能量密度，用这种方法可以实现由多相组成且具有不同非晶到晶态体积比的GST薄膜，这为多级数据存储以及实现具有极低电阻漂移的存储器件提供了可能性。此外，这项工作仅使用一个具有单一脉冲持续时间和单一波长的紫外激光就证明了GST薄膜的非晶化和结晶。总体而言，所呈现的结果为基于Ge-Sb-Te的材料中的开关路径提供了新的视角，并展示了外延Ge-Sb-Te薄膜在先进相变存储概念中的应用潜力。
