xSnSb₂Se₄]]>

摘要

Thin film samples of Ge₉SnSb₂Te₉Se₄, Ge_4.5SnSb₂Te_4.5Se₄, Ge_2.5SnSb₂Te_2.5Se₄, and GeSnSb₂TeSe₄ were prepared via co-sputtering of GeTe and SnSb₂Se₄ and compared to the well-investigated phase change material GeTe. All samples were obtained in an amorphous state. Temperature-dependent in situ X-ray diffraction experiments reveal a crystallization temperature that increases with an increasing SnSb₂Se₄ content, leading to a higher stability of the amorphous phase. The electrical contrast between the amorphous and metastable crystalline state investigated via the van der Pauw method is as large as 4 orders of magnitude up to a 4.5:1 GeTe:SnSb₂Se₄ ratio. Increasing the SnSb₂Se₄ content leads to a decrease in the electrical contrast. Investigations of the samples by applying Fourier transform infrared spectroscopy and variable incident angle spectroscopic ellipsometry show that the optical properties of the amorphous phase are not affected by changes in stoichiometry. In striking contrast, the impact of SnSb₂Se₄ on the optical properties of the crystalline phases is significant: all optical constants decrease because of the reduction in the level of resonant bonding, which leads to a reduced absolute reflectivity of the crystalline phase resulting in a decrease in the optical contrast. These results support the assumption that resonant bonding is crucial for successful optical phase change memory materials.]]>