Ge-Sb-Te基相变材料薄膜：微观结构和原位转变,Chemistry of Materials

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Ge-Sb-Te基相变材料薄膜：微观结构和原位转变
Chemistry of Materials ( IF 7.2 ) Pub Date : 2011-08-17 00:00:00 , DOI: 10.1021/cm200835a
Jan Tomforde ₁ , Wolfgang Bensch ₁ , Lorenz Kienle ₂ , Viola Duppel ₃ , Philipp Merkelbach ₄ , Matthias Wuttig ₄

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三元化合物GeSb ₂ Te ₄和Ge ₂ Sb ₂ Te ₄是有前途的相变材料，可用于数据存储和记录领域。在本研究中，使用磁控溅射技术将材料的薄膜沉积在惰性基板上。通过X射线粉末衍射和高分辨率透射电子显微镜（HRTEM）研究了非晶态，亚稳态和稳定晶态的微观结构。在沉积状态下，材料是无定形的。加热后，它们首先结晶成具有NaCl型结构的亚稳相，然后在较高温度下转变为层状结构（稳定相）。HRTEM研究表明，在所有材料中，具有亚晶形态的纳米级颗粒均处于结晶亚稳态。在GeSb ₂ Te的情况下_{如图4所示}，当样品转变为包含结构空位层的稳定相时，这些纳米晶体不会显着生长。Ge ₂ Sb ₂ Te _4的行为不同。特别地，向晶体稳定相的结构转变伴随着微晶尺寸的显着增加，直至几微米。晶体由纳米级薄片构成，其中不包含空位层。Ge ₂ Sb ₂ Te ₄的X射线数据的Rietveld精修处于亚稳态晶态的化合物表明该化合物由两相组成，其中一相富Ge，另一相贫Ge。前相中相干散射域的大小约为20 nm，而第二相的值确定为约2 nm。

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Thin Films of Ge–Sb–Te-Based Phase Change Materials: Microstructure and in Situ Transformation

The ternary compounds GeSb₂Te₄ and Ge₂Sb₂Te₄ are promising phase change materials for application in the fields of data storage and recording. In the present study, thin films of the materials were deposited on inert substrates using the magnetron sputter technique. The microstructures of the amorphous, metastable, and stable crystalline states were investigated by X-ray powder diffractometry and high resolution transmission electron microscopy (HRTEM). In the as-deposited state, the materials are amorphous. Upon heating, they crystallize first into a metastable phase with a NaCl-type structure, followed by a transformation into a layered structure (stable phase) at higher temperatures. HRTEM studies reveal that nanosized particles with a granular morphology are present in all materials for the crystalline metastable state. In the case of GeSb₂Te₄, these nanocrystals do not grow significantly when the sample transforms to the stable phase, which contains layers of structural vacancy. Ge₂Sb₂Te₄ behaves differently. In particular, the structural transition to the crystalline stable phase is accompanied by a pronounced increase in the crystallite size up to several micrometers. The crystals are built from nanoscale lamellae, which do not contain vacancy layers. Rietveld refinement of the X-ray data of Ge₂Sb₂Te₄ in the metastable crystalline state reveals that the compound consists of two phases of which one is Ge rich and the other Ge poor. The size of the coherent scattering domains in the former phase was about 20 nm, whereas the value for the second phase was determined to be about 2 nm.

更新日期：2011-08-17

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