Cohesive and adhesive properties of ultrathin amorphous and crystalline Ge2Sb2Te5 films on polyimide substrates

In this work, the onset strains of fragmentation, the fracture strength, and fracture toughness of amorphous and crystalline Ge2Sb2Te5 (GST) films are determined. Using in situ methods, such as resistance measurements, reflectance anisotropy spectroscopy (RAS), and light microscopy during uniaxial tensile loading, we demonstrate that onset strain of fragmentation and delamination depend on both, crystallographic state of the GST film and the film thickness. We observe that amorphous GST fractures at larger strains than crystalline GST. However, due to its small Young's modulus the fracture toughness KIC of amorphous GST is lower than that of crystalline GST (amorphous: KIC=0.4±0.2 MPa m0.5; crystalline: KIC=0.8±0.2 MPa m0.5). The results presented are critically discussed with respect to the potential application of GST films in flexible displays.

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