Abstract
A high degree of vacancy ordering is obtained by annealing amorphous GeTe-Sb2Te3 (GST) alloys deposited on a crystalline substrate, which acts as a template for the crystallization. Under annealing the material evolves from amorphous to disordered rocksalt, to ordered rocksalt with vacancies arranged into (111) oriented layers, and finally converts into the stable trigonal phase. The role of the interface in respect to the formation of an ordered crystalline phase is studied by comparing the transformation stages of crystalline GST with and without a capping layer. The capping layer offers another crystallization interface, which harms the overall crystalline quality.
Highlights
Phase-change-material (PCM) based memory is a well established non-volatile electronic memory device
Differences arise from the vacancies configuration depending on the phase. They are randomly distributed in the Ge/Sb layers, while in the trigonal one, they are organized into periodic van der Waals gaps in between two adjacent Te layers
The crystalline phase formed by annealing of a-GST at 110 ◦C for 10 min does not show any VLp in the X-ray diffraction (XRD) profile, and Scanning transmission electron microscopy (STEM) analysis confirms that the sample is in a disordered rocksalt phase with vacancies randomly distributed
Summary
Phase-change-material (PCM) based memory is a well established non-volatile electronic memory device. In 2014 Bragaglia et al.[8] demonstrated that both the metastable c- and stable t-GST phases can be obtained by annealing an amorphous film deposited by molecular beam epitaxy (MBE) on a Si(111) substrate.
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