Investigating the Influence of Resonant Bonding on the Optical Properties of Phase Change Materials (GeTe)xSnSb2Se4

Thin film samples of Ge9SnSb2Te9Se4, Ge4.5SnSb2Te4.5Se4, Ge2.5SnSb2Te2.5Se4, 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...