Thermal annealing studies of GeTe-Sb2Te3 alloys with multiple interfaces

Bragaglia, Valeria; Mio, Antonio Massimiliano; Calarco, Raffaella

doi:10.1063/1.5000338

Cited by 7 publications

(5 citation statements)

References 17 publications

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“…Nanomaterials 2022, 12, x FOR PEER REVIEW 7 of 13 tallization of GST. The reduction of the crystallization temperature in uncapped Ge2Sb2Te5 films exposed to air, due to the selective oxidation of Ge, and to a minor extent of Sb, has been in fact extensively reported in the literature [20][21][22][23][24][25][26]. This behavior has been also recently confirmed in Ge-rich GST [27].…”

Section: Resultsmentioning

confidence: 60%

Crystallization and Electrical Properties of Ge-Rich GeSbTe Alloys

et al. 2022

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Enrichment of GeSbTe alloys with germanium has been proposed as a valid approach to increase the crystallization temperature and therefore to address high-temperature applications of non-volatile phase change memories, such as embedded or automotive applications. However, the tendency of Ge-rich GeSbTe alloys to decompose with the segregation of pure Ge still calls for investigations on the basic mechanisms leading to element diffusion and compositional variations. With the purpose of identifying some possible routes to limit the Ge segregation, in this study, we investigate Ge-rich Sb2Te3 and Ge-rich Ge2Sb2Te5 with low (<40 at %) or high (>40 at %) amounts of Ge. The formation of the crystalline phases has been followed as a function of annealing temperature by X-ray diffraction. The temperature dependence of electrical properties has been evaluated by in situ resistance measurements upon annealing up to 300 °C. The segregation and decomposition processes have been studied by scanning transmission electron microscopy (STEM) and discussed on the basis of density functional theory calculations. Among the studied compositions, Ge-rich Ge2Sb2Te5 is found to be less prone to decompose with Ge segregation.

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Section: Resultsmentioning

confidence: 60%

Crystallization and Electrical Properties of Ge-Rich GeSbTe Alloys

et al. 2022

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“…Thus, it is reasonable to assume that these dark zones correspond to partially empty planes. Indeed the distance between the two adjacent Te planes corresponds to that observed for the vacancy layers formed at the early stage of the cubic to rhombohedral structure change in GST alloys . It is not possible to quantify the fraction of atomic vacancies in these planes from the HAADF‐STEM image shown in Figure b.…”

Section: Resultsmentioning

confidence: 98%

“…Indeed the distance between the two adjacent Te planes corresponds to that observed for the vacancy layers formed at the early stage of the cubic to rhombohedral structure change in GST alloys. [32,38] It is not possible to quantify the fraction of atomic vacancies in these planes from the HAADF-STEM image shown in Figure 7b. As previously mentioned, the contrast over the image is affected by changes of the STEM foil thickness and the low intensity minima in the linescan at the center of the 3.43 nm thick block result from a thinner STEM foil in this zone.…”

Section: Atomic Stacking In a Stoichiometric Superlatticementioning

confidence: 99%

Impact of Stoichiometry on the Structure of van der Waals Layered GeTe/Sb₂Te₃ Superlattices Used in Interfacial Phase‐Change Memory (iPCM) Devices

Kowalczyk

Hippert

Bernier

et al. 2018

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Van der Waals layered GeTe/Sb Te superlattices (SLs) have demonstrated outstanding performances for use in resistive memories in so-called interfacial phase-change memory (iPCM) devices. GeTe/Sb Te SLs are made by periodically stacking ultrathin GeTe and Sb Te crystalline layers. The mechanism of the resistance change in iPCM devices is still highly debated. Recent experimental studies on SLs grown by molecular beam epitaxy or pulsed laser deposition indicate that the local structure does not correspond to any of the previously proposed structural models. Here, a new insight is given into the complex structure of prototypical GeTe/Sb Te SLs deposited by magnetron sputtering, which is the used industrial technique for SL growth in iPCM devices. X-ray diffraction analysis shows that the structural quality of the SL depends critically on its stoichiometry. Moreover, high-angle annular dark-field-scanning transmission electron microscopy analysis of the local atomic order in a perfectly stoichiometric SL reveals the absence of GeTe layers, and that Ge atoms intermix with Sb atoms in, for instance, Ge Sb Te blocks. This result shows that an alternative structural model is required to explain the origin of the electrical contrast and the nature of the resistive switching mechanism observed in iPCM devices.

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“…The transition temperature is strongly dependent on the heating rate, interfaces and composition of the particular alloy. 26,63,64…”

Section: Local Structure Of Chalcogenidebased Phase Change Alloysmentioning

confidence: 99%