Growth and microstructure of GeTe-Sb2Te3 heterostructures prepared by pulsed laser deposition

Chalcogenide based heterostructures turned out to be a promising approach to further improve outstanding properties of phase change memory materials. For future applications, a deep understanding of the interplay of local structure and properties is crucial. Here, GeTe-Sb2Te3 based heterostructures (HSs) are grown by pulsed laser deposition onto SiO2/Si substrates at room temperature. By combining advanced transmission electron microscopy with X-ray measurement techniques, the influence of systematically varied deposition parameters on the microstructure is analyzed in-depth. Experimental results reveal that the growth rate of GeTe and Sb2Te3 layers depends on laser pulse energy. Nanoscale spectroscopic characterization of the HSs shows interdiffusion of Ge/Sb into Sb2Te3/GeTe layers, respectively. The in-diffusion depends on the layer thickness and deposition parameters. For the lowest laser energy, it leads to the formation of ternary Ge-Sb-Te layer. Whereas GeTe and Ge-Sb-Te are found to be amorphous within the HSs, Sb2Te3 is crystalline in all thin films although some disordered regions are found additionally. Moreover, Sb2Te3 is formed in cubic, vacancy ordered and trigonal structures and contains bilayer as well as twin defects. Overall, this work provides insights into the growth and microstructure of the HSs, which give the reasons for the outstanding performance of Sb2Te3-GeTe HSs.