Atomic stacking and van-der-Waals bonding in GeTe–Sb<sub>2</sub>Te<sub>3</sub> superlattices

Momand, Jamo; Lange, Felix; Wang, Ruining; Boschker, Jos E.; Verheijen, Marcel A.; Calarco, Raffaella; Wuttig, Matthias; Kooi, Bart J.

doi:10.1557/jmr.2016.334

Cited by 58 publications

(71 citation statements)

References 49 publications

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“…. Based on our present observation of atomic stacking in the Ge–Sb–Te block, as well as those of previous studies, one can conclude that the innermost Ge/Sb planes are Ge‐rich, while the Ge/Sb planes closer to vdW gaps are Sb‐rich. Although intermixing mostly results in the formation of Ge–Sb–Te blocks similar to those present in the stable alloys belonging to the pseudo‐binary line in the Ge–Sb–Te ternary diagram, we have reported that much more disordered zones also exist in the SL.…”

Section: Resultssupporting

confidence: 88%

“…Besides, an influence of the GeTe thickness can be excluded by the present study. Intermixing has been reported in SLs deposited by sputtering with a 4 nm thick GeTe layer, which is far above the ideal thickness proposed in the design rules of iPCM devices . The GeTe layer thickness in the present study was chosen to match the ideal value proposed in Ref.…”

Section: Resultsmentioning

confidence: 98%

“…The a value measured on a 100 nm thick Sb 2 Te 3 film deposited by cosputtering in the same conditions as the SLs with 20 W RF power applied to the Te target is also given. The a values of bulk GeTe, Ge 2 Sb 2 Te 5 , and Sb 2 Te 3 alloys are shown for comparison. Error bars (±0.0002 nm) are smaller than the symbol size.…”

Section: Resultsmentioning

confidence: 99%

“…One explanation could be that the SL structure depends on the deposition method and/or on the thickness of the deposited GeTe layer. Indeed, intermixing has been reported in sputtered SLs with a much thicker GeTe layer (4 nm) …”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultssupporting

confidence: 88%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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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“…If there is no chemical disorder, two cationic-like layers should have the same brightness as the Te layers, as the atomic number of Sb (51) is very close to that of Te (52). Other possible forms of disorder in hexagonal GST include stacking faults, twinning and vacancy layer intersections, antisites and so on [72,73,74]. …”

Section: Discussionmentioning

confidence: 99%

A Review on Disorder-Driven Metal–Insulator Transition in Crystalline Vacancy-Rich GeSbTe Phase-Change Materials

Wang

Mazzarello

et al. 2017

Materials

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Metal–insulator transition (MIT) is one of the most essential topics in condensed matter physics and materials science. The accompanied drastic change in electrical resistance can be exploited in electronic devices, such as data storage and memory technology. It is generally accepted that the underlying mechanism of most MITs is an interplay of electron correlation effects (Mott type) and disorder effects (Anderson type), and to disentangle the two effects is difficult. Recent progress on the crystalline Ge1Sb2Te4 (GST) compound provides compelling evidence for a disorder-driven MIT. In this work, we discuss the presence of strong disorder in GST, and elucidate its effects on electron localization and transport properties. We also show how the degree of disorder in GST can be reduced via thermal annealing, triggering a disorder-driven metal–insulator transition. The resistance switching by disorder tuning in crystalline GST may enable novel multilevel data storage devices.

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2D or Not 2D: Strain Tuning in Weakly Coupled Heterostructures

Wang

Lange

Cecchi

et al. 2018

Adv Funct Materials

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A route to realize strain engineering in weakly bonded heterostructures is presented. Such heterostructures, consisting of layered materials with a pronounced bond hierarchy of strong and weak bonds within and across their building blocks respectively, are anticipated to grow decoupled from each other. Hence, they are expected to be unsuitable for strain engineering as utilized for conventional materials which are strongly bonded isotropically. Here, it is shown for the first time that superlattices of layered chalcogenides (Sb 2 Te 3 / GeTe) behave neither as fully decoupled two-dimensional (2D) materials nor as covalently bonded three-dimensional (3D) materials. Instead, they form a novel class of 3D solids with an unparalleled atomic arrangement, featuring a distribution of lattice constants, which is tunable. A map to identify further material combinations with similar characteristic is given. It opens the way for the design of a novel class of artificial solids with unexplored properties.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201705901.dichalcogenides (e.g., MoSe 2 , WSe 2 , TiTe 2 , etc.), and quintuple layered V 2 -VI 3 chalcogenides (e.g., Sb 2 Te 3 , Bi 2 Te 3 , and Bi 2 Se 3 ). Even septuple, nontuple, and more complex layered systems can be created when alloying the latter class of materials with IV-VI chalcogenides like GeTe, SnTe, or PbTe.The weak interlayer interaction-which causes the 2D nature of these materials-is both a blessing and a curse. On the one hand, it allows the growth of heterostructures and superlattices of dissimilar 2D materials without epitaxial guidance (vdW epitaxy). [7] Yet, it also creates adverse side effects such as poor adhesion [7] and wetting. [8] More importantly, the weak coupling impedes strain engineering. [9][10][11][12] Clearly, in the limit of zero coupling across vdW gaps, it should be impossible to introduce any strain in the growing 2D film. Yet, if enough coupling prevails across these gaps, strain engineering should be possible, too. The engineering of strain is an elegant concept to tailor physical properties without changing composition. Heteroepitaxial growth provides a versatile platform to create such strained films on appropriately chosen substrates. A manifold of novel devices have been realized by strain control, such as MOSFET transistors with strained Si, leading to 80-120% gains in electron mobility, [13,14] or quantum cascade lasers, where the growth of thicker defect-free quantum wells shortens the operation wavelengths. [15] Hence, strain engineering is also subject of numerous publications dealing with 2D systems. [16][17][18][19][20][21][22] It requires an understanding and possibly tailoring of the coupling across vdW gaps. With this goal in mind, we have investigated GeTe/Sb 2 Te 3 superlattices (SLs). These layered systems are currently attracting significant scientific interest for next-generation data storage media based on phase-change materials (interfacial pha...

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Atomic stacking and van-der-Waals bonding in GeTe–Sb₂Te₃ superlattices

Abstract: Abstract

Cited by 58 publications

References 49 publications

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

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

A Review on Disorder-Driven Metal–Insulator Transition in Crystalline Vacancy-Rich GeSbTe Phase-Change Materials

2D or Not 2D: Strain Tuning in Weakly Coupled Heterostructures

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Atomic stacking and van-der-Waals bonding in GeTe–Sb2Te3 superlattices

Abstract: Abstract

Cited by 58 publications

References 49 publications

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

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

A Review on Disorder-Driven Metal–Insulator Transition in Crystalline Vacancy-Rich GeSbTe Phase-Change Materials

2D or Not 2D: Strain Tuning in Weakly Coupled Heterostructures

Contact Info

Product

Resources

About

Atomic stacking and van-der-Waals bonding in GeTe–Sb₂Te₃ superlattices

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

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