Materials Screening for Disorder‐Controlled Chalcogenide Crystals for Phase‐Change Memory Applications

Xu, Yazhi; Wang, Xudong; Zhang, Wei; Schäfer, Lisa; Reindl, Johannes; Bruch, Felix vom; Zhou, Yuxing; Evang, Valentin; Wang, Jiangjing; Deringer, Volker L.; Ma, E.; Wuttig, Matthias; Mazzarello, Riccardo

doi:10.1002/adma.202006221

Cited by 33 publications

(44 citation statements)

References 72 publications

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“…The latter is also obtained at very high annealing temperatures over long annealing time. Starting from the amorphous phase of Sb 2 Te 3 , the thermal energy at elevated temperatures firstly drives a rapid transition into the metastable rocksalt phase, then induces a second transition toward the layered rhombohedral phase via vacancy ordering, [94] similarly to the behavior of GST. [109][110][111] The high concentration of atomic vacancies in rocksalt Sb 2 Te 3 and GST ensures that the average number of valence p electrons per site is equal to 3.…”

Section: Resultsmentioning

confidence: 99%

“…[92] Besides the stable rhombohedral phase, a metastable rocksalt-like phase is known for Sb 2 Te 3 , in which 1/3 lattice sites in the Sb sublattice are vacant (Figure S3, Supporting Information). [93,94] The Sb 8 Te 9 crystal shows a very long c lattice parameter (>10 nm) with 3 alternately stacked atomic blocks, each of which contains 3 Sb 2 Te 3 QLs þ 1 Sb 2 bilayer (BL). [95] Regarding c-Sb 4 Te 3 , two stacking sequences are known.…”

Section: Resultsmentioning

confidence: 99%

“…[109][110][111] The high concentration of atomic vacancies in rocksalt Sb 2 Te 3 and GST ensures that the average number of valence p electrons per site is equal to 3. [94,112] This configuration enables metavalent bonding, [113][114][115][116][117] which is a generic bonding mechanism in crystalline PCMs. If a rocksalt Sb 8 Te 9 structure is built, the excess p electrons brought by the additional Sb atoms push up the E F into the antibonding region, inducing some chemical instability (Figure S3, Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

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Change in Structure of Amorphous Sb–Te Phase‐Change Materials as a Function of Stoichiometry

Ahmed

Wang

et al. 2021

Physica Rapid Research Ltrs

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The concept of phase-change memory using chalcogenide glasses dates back to the 1960s, as pioneered by Ovshinsky. [1] Starting from late 1980s, Ge-Sb-Te alloys along the GeTe-Sb 2 Te 3 pseudo-binary line (Group I), such as Ge 2 Sb 2 Te 5 , Ge 1 Sb 2 Te 4 and Ge 8 Sb 2 Te 11 , [2][3][4][5] doped Sb 2þx -Te alloys (Group II), such as Ag-, In-doped Sb 2þx Te (AIST), and alloyed Sb (Group III), [6][7][8][9][10] such as Ge 15 Sb 85 , were identified as suitable PCMs. These alloys were initially used for the rewritable optical data storage industry. [11] More recently, the Ge 1 Sb 2 Te 4 (GST) alloy has been used as the core material for electronic non-volatile memories, [12][13][14][15][16][17][18][19] e.g., 3D Xpoint. Moreover, PCMs can be used for neuro-inspired computing and in-memory computing, [20][21][22][23][24][25][26][27] and could also enable various nonvolatile photonic applications, including memory and computing devices, switches, and displays. [28][29][30][31][32][33][34][35][36] PCMs utilize the significant contrast in electrical resistivity or optical reflectivity between their crystalline and amorphous phase to encode data. [11] The switching between the two logic states is achieved by rapid and reversible phase transitions, namely, SET (crystallization) and RESET (melt-quenched amorphization). In addition to binary storage, multiple resistivity or reflectivity states can be obtained within a PCM cell via partial amorphization (iterative RESET) and crystallization (accumulative SET), enabling multilevel storage [37,38] and neuro-inspired computing applications. [39,40]

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Change in Structure of Amorphous Sb–Te Phase‐Change Materials as a Function of Stoichiometry

Ahmed

Wang

et al. 2021

Physica Rapid Research Ltrs

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“…In the last two sections, we have already seen examples of how advanced technologies enable electronic mimics of individual parts of the neural system with demonstrated simple computational functionalities. We do not intend to survey the neuromorphic hardware implementation again as this has been done in numerous reviews, just to name a few, at materials level, [ 48,661–722 ] at device level, [ 10,244,263,723–790 ] at more circuit level, or above. [ …”

Section: Implementation Levelmentioning

confidence: 99%

A Marr's Three‐Level Analytical Framework for Neuromorphic Electronic Systems

Guo

Zou

et al. 2021

Advanced Intelligent Systems

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Neuromorphic electronics, an emerging field that aims for building electronic mimics of the biological brain, holds promise for reshaping the frontiers of information technology and enabling a more intelligent and efficient computing paradigm. As their biological brain counterpart, the neuromorphic electronic systems are complex, having multiple levels of organization. Inspired by David Marr's famous three‐level analytical framework developed for neuroscience, the advances in neuromorphic electronic systems are selectively surveyed and given significance to these research endeavors as appropriate from the computational level, algorithmic level, or implementation level. Under this framework, the problem of how to build a neuromorphic electronic system is defined in a tractable way. In conclusion, the development of neuromorphic electronic systems confronts a similar challenge to the one neuroscience confronts, that is, the limited constructability of the low‐level knowledge (implementations and algorithms) to achieve high‐level brain‐like (human‐level) computational functions. An opportunity arises from the communication among different levels and their codesign. Neuroscience lab‐on‐neuromorphic chip platforms offer additional opportunity for mutual benefit between the two disciplines.

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“…The unique property of GeTe-Sb 2 Te 3 also makes it an excellent candidate for various applications in computer science, especially in the field of non-volatile computer memory [4,5]. Important progress has been achieved in the past 20 years to develop new phase change materials and understand their phase change mechanisms [6][7][8][9][10][11][12][13][14][15]. It has been known that local interactions between atoms play an important role in phase changes [4,16].…”

Section: Introductionmentioning

confidence: 99%

Unusual Force Constants Guided Distortion-Triggered Loss of Long-Range Order in Phase Change Materials

et al. 2021

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Unusual force constants originating from the local charge distribution in crystalline GeTe and Sb2Te3 are observed by using the first-principles calculations. The calculated stretching force constants of the second nearest-neighbor Sb-Te and Ge-Te bonds are 0.372 and −0.085 eV/Å2, respectively, which are much lower than 1.933 eV/Å2 of the first nearest-neighbor bonds although their lengths are only 0.17 Å and 0.33 Å longer as compared to the corresponding first nearest-neighbor bonds. Moreover, the bending force constants of the first and second nearest-neighbor Ge-Ge and Sb-Sb bonds exhibit large negative values. Our first-principles molecular dynamic simulations also reveal the possible amorphization of Sb2Te3 through local distortions of the bonds with weak and strong force constants, while the crystalline structure remains by the X-ray diffraction simulation. By identifying the low or negative force constants, these weak atomic interactions are found to be responsible for triggering the collapse of the long-range order. This finding can be utilized to guide the design of functional components and devices based on phase change materials with lower energy consumption.

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Materials Screening for Disorder‐Controlled Chalcogenide Crystals for Phase‐Change Memory Applications

Cited by 33 publications

References 72 publications

Change in Structure of Amorphous Sb–Te Phase‐Change Materials as a Function of Stoichiometry

Change in Structure of Amorphous Sb–Te Phase‐Change Materials as a Function of Stoichiometry

A Marr's Three‐Level Analytical Framework for Neuromorphic Electronic Systems

Unusual Force Constants Guided Distortion-Triggered Loss of Long-Range Order in Phase Change Materials

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