Atomic structure and dynamic reconfiguration of layered defects in van der Waals layered Ge-Sb-Te based materials

Lotnyk, Andriy; Roß, Ulrich; Dankwort, Torben; Hilmi, Isom; Kienle, Lorenz; Rauschenbach, B.

doi:10.1016/j.actamat.2017.09.012

Acta Materialia

2017

DOI: 10.1016/j.actamat.2017.09.012

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Atomic structure and dynamic reconfiguration of layered defects in van der Waals layered Ge-Sb-Te based materials

Andriy Lotnyk

Ulrich Roß

Torben Dankwort

et al.

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Cited by 64 publications

(61 citation statements)

References 33 publications

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“…Then, we focused the electron beam to the boxed region for 20 min. Clearly, the three bilayers move rightward upon irradiation, as indicated by the orange arrows in Figure a,b.This local structural rearrangement process is in line with the layer‐switching process observed in layer‐structured GST under electron beam irradiation and heat . The chemical details of the rearranged bilayers were further assessed by EDX mapping experiments, which show that the chemical distribution of bilayers remains the same after irradiation (Figure S3, Supporting Information).…”

supporting

confidence: 70%

“…Instead of unconstrained phase transitions between the amorphous and crystalline state, short‐range phase transitions through local rearrangements, such as layer‐switching between two‐layered crystalline states of GST, are proposed for iPCM. Although this switching mechanism is still under debate, layer‐switching has been shown to occur in layer‐structured GST through swapped bilayers . The intermixing of Sb and Te has been proven to be essential for the stabilization of the swapped bilayers .…”

mentioning

confidence: 99%

“…These bilayer defects appear in series and are found frequently in the sputtered samples. They were suggested to be the key element for layer‐switching in iPCMs by triggering the reconfiguration of vdW‐like gaps …”

mentioning

confidence: 99%

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Layer‐Switching Mechanisms in Sb₂Te₃

Wang

et al. 2019

Physica Rapid Research Ltrs

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Interfacial phase‐change memory (iPCM) based on layer‐structured Ge‐Sb‐Te crystals has been recently proposed, offering an energy‐efficient implementation of nonvolatile memory cells and supplementing the development of Ge‐Sb‐Te‐based phase‐change random access memories (PRAMs). Although the working principle of iPCM is still under debate, it is believed that layer‐switching plays a role in the switching process between the low‐resistance and high‐resistance states of iPCM memory cells. However, the role of Ge in forming swapped bilayers—the key elements for layer‐switching—is not yet clarified. This work manages to achieve layer‐switching in Sb2Te3 thin films by manipulating the formation of bilayer defects using magnetron sputtering and post‐thermal annealing. By combining scanning transmission electron microscopy (STEM) experiments with density functional theory (DFT) calculations, the essential role of Sb‐Te intermixing is elucidated in stabilizing swapped bilayers at a low energy cost. In situ STEM experiments provide a real‐time and real‐space view of dynamical reconfiguration of van der Waals‐like gaps in Sb2Te3 thin films under electron‐beam irradiation. The results show that the Ge atoms are not necessary for the formation and motion of swapped bilayers, providing atomic insights on the layer‐switching mechanism in layer‐structured binary and ternary group V‐ and IV–V‐tellurides for memory applications.

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supporting

confidence: 70%

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confidence: 99%

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Layer‐Switching Mechanisms in Sb₂Te₃

Wang

et al. 2019

Physica Rapid Research Ltrs

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“…Therefore, we did not observe a significant peak shift in the GeTe A 1 mode whereas we observed a relatively large shift for the Sb 2 Te 3 A 2 1g mode. This observation corresponds to the fact that when Ge atoms diffuse into Sb 2 Te 3 layers the tensile strain in the GeTe layer is relatively small compared to that in the Sb 2 Te 3 layers. We note that the results for chalcogenide SL samples with varying Sb 2 Te 3 thickness are not shown because the FLA peak is masked by the much stronger Sb 2 Te 3 A 1 1g mode at ≈2 THz.…”

mentioning

confidence: 91%

“…However, it has recently been argued that the periodicity of the SL structure may significantly differ from the proposed stacking of GeTe and Sb 2 Te 3 . Such variations would give rise to aperiodic van der Waals (vdW) gaps in the SL structure, which may lead to degradation of device performance.…”

mentioning

confidence: 99%

All‐Optical Detection of Periodic Structure of Chalcogenide Superlattice Using Coherent Folded Acoustic Phonons

Saito

Fons

Kolobov

et al. 2018

Physica Rapid Research Ltrs

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Chalcogenide superlattices (SL) consist of alternately stacked GeTe and Sb2Te3 layers. The structure can act as a 3D topological insulator depending on the constituent layer thicknesses, making the design of the SL period a central issue for advancing chalcogenide SL as potential candidates for spin devices as well as for optimization of the current generation of phase‐change memory devices. Here we explore the periodic structure of chalcogenide SL by observing coherent folded longitudinal acoustic (FLA) phonons excited by femtosecond laser pulse irradiation. The peak frequency of the FLA modes is observed to change upon variation of the thickness of the GeTe layer, which is well reproduced by means of an elastic continuum model. In addition, a new SL structure is unveiled for a sample consisting of thin GeTe and Sb2Te3 layers, which suggests intermixing of Ge atoms. This all‐optical technique based on observation of coherent FLA modes offers a non‐destructive characterization of superlattice structures at atomic resolution.

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Phase‐Change Superlattice Materials toward Low Power Consumption and High Density Data Storage: Microscopic Picture, Working Principles, and Optimization

Chen

Wang

et al. 2018

Adv Funct Materials

133

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To meet the requirement of big data era and neuromorphic computations, nonvolatile memory with fast speed, high density, and low power consumption is urgently needed. As an emerging technology, phase-change memory is a promising candidate to solve this problem. However, the drawback of the high power consumption hinders their applications. Most recently, a new phase-change material of [(GeTe) x /(Sb 2 Te 3 ) y ] n superlattice attracts intensive attentions owing to its ultralow power consumption comparing with conventional phase-change memory devices. Many studies on this new material have been reported. However, there still lacks a comprehensive and unified understanding of its atomic picture and working mechanism. This article at first summarizes the broad applications for phase-change materials. Then, the major progresses of phase-change superlattices to understand the microscopic structure and working principles for data storage are discussed. Strategies on material optimizations to further enhance device performances are proposed. Finally, an outlook on new applications with these advanced superlattice materials is suggested.

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Atomic structure and dynamic reconfiguration of layered defects in van der Waals layered Ge-Sb-Te based materials

Cited by 64 publications

References 33 publications

Layer‐Switching Mechanisms in Sb₂Te₃

Layer‐Switching Mechanisms in Sb₂Te₃

All‐Optical Detection of Periodic Structure of Chalcogenide Superlattice Using Coherent Folded Acoustic Phonons

Phase‐Change Superlattice Materials toward Low Power Consumption and High Density Data Storage: Microscopic Picture, Working Principles, and Optimization

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Atomic structure and dynamic reconfiguration of layered defects in van der Waals layered Ge-Sb-Te based materials

Cited by 64 publications

References 33 publications

Layer‐Switching Mechanisms in Sb2Te3

Layer‐Switching Mechanisms in Sb2Te3

All‐Optical Detection of Periodic Structure of Chalcogenide Superlattice Using Coherent Folded Acoustic Phonons

Phase‐Change Superlattice Materials toward Low Power Consumption and High Density Data Storage: Microscopic Picture, Working Principles, and Optimization

Contact Info

Product

Resources

About

Layer‐Switching Mechanisms in Sb₂Te₃

Layer‐Switching Mechanisms in Sb₂Te₃