Ab initio molecular dynamics and materials design for embedded phase-change memory

Sun, L.; Zhou, Yuxing; Wang, Xudong; Chen, Yuhan; Deringer, Volker L.; Mazzarello, Riccardo; Zhang, Wei

doi:10.1038/s41524-021-00496-7

Cited by 51 publications

(45 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As an example of this methodology, we have computed the decomposition map of the three alloys, GST312, GST412 and GST512, on the Ge-GST124 pseudobinary line, whose amorphous phase was investigated by DFT simulations in Ref. [ 27 ].…”

Section: Resultsmentioning

confidence: 99%

“…The phase separation itself is believed to be the origin of the raise of

because of the mass transport on a long length scale involved in phase segregation [ 22 ]. However, previous analysis of DFT models of the amorphous phase as a function of composition revealed that moving away from the GeTe-Sb

tie-line by increasing either the Ge or Sb content along the Ge-GST124 [ 27 ], Sb-GeTe [ 56 ] and Ge-Sb

lines [ 42 ], leads to an amorphous network which is more and more dissimilar from the cubic crystal. In the rocksalt phase, all atoms are in an octahedral bonding geometry with no homopolar bonds.…”

Section: Resultsmentioning

confidence: 99%

“…Atomistic simulations can provide useful information in this respect. In a very recent work, for instance, molecular dynamics simulations based on Density Functional Theory (DFT) were applied to study the amorphous phase of Ge-rich GST along the Ge-GST124 pseudobinary line [ 27 ]. The simulations revealed that the amorphous phase is stable with respect to phase separation into amorphous Ge and amorphous GST124 only for Ge content below or equal to 50 atomic %.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High-Throughput Calculations on the Decomposition Reactions of Off-Stoichiometry GeSbTe Alloys for Embedded Memories

Kheir

Bernasconi

2021

Nanomaterials

View full text Add to dashboard Cite

Chalcogenide GeSbTe (GST) alloys are exploited as phase change materials in a variety of applications ranging from electronic non-volatile memories to neuromorphic and photonic devices. In most applications, the prototypical Ge2Sb2Te5 compound along the GeTe-Sb2Te3 pseudobinary line is used. Ge-rich GST alloys, off the pseudobinary tie-line with a crystallization temperature higher than that of Ge2Sb2Te5, are currently explored for embedded phase-change memories of interest for automotive applications. During crystallization, Ge-rich GST alloys undergo a phase separation into pure Ge and less Ge-rich alloys. The detailed mechanisms underlying this transformation are, however, largely unknown. In this work, we performed high-throughput calculations based on Density Functional Theory (DFT) to uncover the most favorable decomposition pathways of Ge-rich GST alloys. The knowledge of the DFT formation energy of all GST alloys in the central part of the Ge-Sb-Te ternary phase diagram allowed us to identify the cubic crystalline phases that are more likely to form during the crystallization of a generic GST alloy. This scheme is exemplified by drawing a decomposition map for alloys on the Ge-Ge1Sb2Te4 tie-line. A map of decomposition propensity is also constructed, which suggests a possible strategy to minimize phase separation by still keeping a high crystallization temperature.

show abstract

Section: Resultsmentioning

confidence: 99%

“…The phase separation itself is believed to be the origin of the raise of

tie-line by increasing either the Ge or Sb content along the Ge-GST124 [ 27 ], Sb-GeTe [ 56 ] and Ge-Sb

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

High-Throughput Calculations on the Decomposition Reactions of Off-Stoichiometry GeSbTe Alloys for Embedded Memories

Kheir

Bernasconi

2021

Nanomaterials

View full text Add to dashboard Cite

show abstract

“…The shorter the interatomic distance, the higher the bond population. Following our previous work, [106][107][108] we multiply the B AB by the RDF and obtain the "bond-weighted distribution function" BWDF ¼ P B>A ½δðr À jr AB jÞ Â B AB for the six amorphous alloys. The crossover from positive to negative values in the BWDFs determines a threshold for covalent interactions.…”

Section: Resultsmentioning

confidence: 99%

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

Ahmed

Wang

et al. 2021

Physica Rapid Research Ltrs

Self Cite

View full text Add to dashboard Cite

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]

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

Ab initio molecular dynamics and materials design for embedded phase-change memory

Cited by 51 publications

References 80 publications

High-Throughput Calculations on the Decomposition Reactions of Off-Stoichiometry GeSbTe Alloys for Embedded Memories

High-Throughput Calculations on the Decomposition Reactions of Off-Stoichiometry GeSbTe Alloys for Embedded Memories

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

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

Contact Info

Product

Resources

About