Ab‐initio calculations and structural studies of (SiTe)2(Sb2Te3)n (n: 1, 2, 4 and 6) phase‐change superlattice films

Saito, Yuta; Tominaga, Junji; Fons, Paul; Kolobov, A. V.; Nakano, Takashi

doi:10.1002/pssr.201409013

Cited by 31 publications

(21 citation statements)

References 19 publications

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“…For one sample, a chalcogenide film was deposited directly onto the substrate (iii), while for another piece of the same sample, surface sputtering using Ar was carried out prior to film deposition ((iv) and (v)). It should be noted that not only was an Sb

_{2}

_{3}

single film deposited but also GeTe/Sb

_{2}

_{3}

and SiTe/Sb

_{2}

_{3}

superlattice films were fabricated in order to test the application of this method for the fabrication of PCRAM . In all cases, an Sb

_{2}

_{3}

film was initially deposited to allow for the growth of highly oriented GeTe or SiTe compounds ().…”

Section: Experimental Methodsmentioning

confidence: 99%

Self‐organized van der Waals epitaxy of layered chalcogenide structures

Saito

Fons

Kolobov

et al. 2015

Phys. Status Solidi B

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Highly oriented Sb2Te3 films were successfully deposited by RF‐magnetron sputtering on both crystalline and amorphous substrates. A novel deposition mechanism and method are proposed based on van der Waals epitaxy. Due to the selective reactivity of the top surface atoms of the substrate with sputtered atoms, a Te monolayer is the first layer formed on the substrate, resulting in the subsequent layer‐by‐layer growth of the Sb2Te3 film independent of the crystallinity of the substrates. We believe that this method can be applied to the mass production of a wide range of various van der Waals solids, such as transition metal dichalcogenides and topological insulators for future electronics devices.

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_{2}

_{3}

single film deposited but also GeTe/Sb

_{2}

_{3}

and SiTe/Sb

_{2}

_{3}

superlattice films were fabricated in order to test the application of this method for the fabrication of PCRAM . In all cases, an Sb

_{2}

_{3}

film was initially deposited to allow for the growth of highly oriented GeTe or SiTe compounds ().…”

Section: Experimental Methodsmentioning

confidence: 99%

Self‐organized van der Waals epitaxy of layered chalcogenide structures

Saito

Fons

Kolobov

et al. 2015

Phys. Status Solidi B

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“…Liu et al reported a multilayer [(SnSb 4 ) 30 nm /(SbSe) 20 nm ] 1 film that possessed fast switching speed (<5 ns) and good thermal stability (ten‐year‐retention temperature = 122 °C) . Saito et al also predicted that the [(SiTe) 2 /(Sb 2 Te 3 ) y ] superlattice may be a possible phase change materials . To summarize, the advantages of superlattice or superlattice‐like phase change materials do not exclusively rely on the composition of [(GeTe) x /(Sb 2 Te 3 ) y ] n .…”

Section: Optimization Of Superlattice For Advanced Performancementioning

confidence: 99%

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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“…52 Some attempts to replace Ge by different elements have also been reported; tuning the composition has an even greater possibility of further improving iPCM performance. 53,54 In conclusion, we have explored the structural dynamics and electronic structural changes in We also note that the presence of both Ge and Sb atoms on cation planes adjacent to vdW gaps, i.e. Ge/Sb intermixing, is crucial for the iPCM switching.…”

mentioning

confidence: 94%

Origin of resistivity contrast in interfacial phase-change memory: The crucial role of Ge/Sb intermixing

Saito

Kolobov

Fons

et al. 2019

Applied Physics Letters

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Phase-change memories based on reversible amorphous-crystal transformations in pseudobinary GeTe-Sb2Te3 alloys are one of the most promising non-volatile memory technologies. The recently proposed superlattice-based memory, or interfacial phase change memory (iPCM), is characterized by significantly faster switching, lower energy consumption and better endurance. The switching mechanism in iPCM, where both the SET and RESET states are crystalline, is still contentious. Here, using the ab initio density functional theory simulations, a conceptually new switching mechanism for iPCM is derived, which is based on the change in potential landscape of the band-gap, associated with local deviations from the pseudo-binary stoichiometry across the van der Waals gaps, and the associated shift of the Fermi level. The crucial role in this process belongs to Ge/Sb intermixing on the cation planes of iPCM. These findings offer a comprehensive understanding of the switching mechanisms in iPCM and are an essential step forward to the insightful development of phase-change memory technology. Phase change random access memory (PCRAM) is one of the most promising candidates for the next generation non-volatile memory with phase change materials forming a key component of the recently commercialized 3D XPoint memory technology where sophisticated three-dimensional integration of chalcogenide-based memory and selector components enables much faster writing speeds than Flash and denser capacity than dynamic random access memory (DRAM). 1,2 The development of phase-change materials dates back over three decades, with the most studied materials being Ge-Sb-Te (GST) ternary alloys on the GeTe-Sb2Te3 pseudobinary tie-line, and which found great success in optical disc devices. 3 On the other hand, as optical disc and non-volatile memories clearly have very different requirements, the required material properties also differ. Using the same material, GST alloys, for PCRAM memories does not in itself solve the various difficulties in developing non-volatile memories. A major breakthrough in PCRAM materials was the development of interfacial phase change memory (iPCM) inspired by the Ge-atom flip-flop model. 4-8 In iPCM, the two binary end compounds of the GeTe-Sb2Te3 pseudobinary tie line, GeTe and Sb2Te3, are alternately stacked to form an atomically aligned superlattice structure with van der Waals (vdW) gaps separating covalently bonded blocks. Devices based upon iPCM showed excellent performance such as ultra-low power consumption, faster switching speeds, and longer endurance than conventional alloy-type PCRAM. 4,9 After the development of chalcogenide superlattices and their devices based on GeTe/Sb2Te3 superlattices fabricated from sputter-deposited films, 4,10-13 several specific switching models were proposed based on the idea of bi-layer switching within GeTe blocks. 14-20 In particular switching between inverted Petrov and Ferro structures (Figure 1) was proposed based on the arguments that the relative stability of these two pha...

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Ab‐initio calculations and structural studies of (SiTe)₂(Sb₂Te₃)_n (n: 1, 2, 4 and 6) phase‐change superlattice films

Cited by 31 publications

References 19 publications

Self‐organized van der Waals epitaxy of layered chalcogenide structures

Self‐organized van der Waals epitaxy of layered chalcogenide structures

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

Origin of resistivity contrast in interfacial phase-change memory: The crucial role of Ge/Sb intermixing

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