Phase‐Change Memory Materials by Design: A Strain Engineering Approach

Zhou, Xilin; Kalikka, Janne; Ji, Xinglong; Wu, Liangcai; Zhang, Song; Simpson, Robert E.

doi:10.1002/adma.201505865

Cited by 133 publications

(117 citation statements)

References 53 publications

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“…They calculated a switching energy barrier for both models of about 2.5–2.7 eV, close to the experiment value12. Thus, the CSL switching process was modeled as a change of stacking sequence in chemically pure layers, without any change in atomic coordination numbers141516. It differs from the local displacive transition of the crystalline to amorphous phase transition in bulk GeSbTe systems1718, where the Ge coordination number changes, and from the thermally driven process of the thicker superlattice devices5.…”

supporting

confidence: 58%

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

Robertson

2016

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GeSbTe-based chalcogenide superlattice (CSLs) phase-change memories consist of GeSbTe layer blocks separated by van der Waals bonding gaps. Recent high resolution electron microscopy found two types of disorder in CSLs, a chemical disorder within individual layers, and SbTe bilayer stacking faults connecting one block to an adjacent block which allows individual block heights to vary. The disorder requires a generalization of the previous switching models developed for CSL systems. Density functional calculations are used to describe the stability of various types of intra-layer disorder, how the block heights can vary by means of SbTe-based stacking faults and using a vacancy-mediated kink motion, and also to understand the nature of the switching process in more chemically disordered CSLs.

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confidence: 58%

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

Robertson

2016

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“…This stems mainly from the lack of information on the structure of the GeTe/Sb 2 Te 3 SLs in the two resistance states. SLs incorporated in iPCM are deposited by physical vapor deposition (PVD) magnetron sputtering. Besides, the growth of epitaxial single crystalline vdW layered SLs has been achieved by molecular beam epitaxy (MBE) on Sb‐passivated Si (111) surface .…”

Section: Introductionmentioning

confidence: 99%

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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“…Information can be stored in the phase of the material and read by measuring the resistance 2 . PCM has received considerable attention owing to its compatibility with existing complementary metal-oxide semiconductor (CMOS) technologies, remarkable read/write speeds (20 ns/10 ns), long cycle life (greater than 10 12 ), and low environment influence 3 . However, the main limitation of PCM is the large power consumption of these devices.…”

Section: Introductionmentioning

confidence: 99%

Suppression for an intermediate phase in ZnSb films by NiO-doping

Wang

et al. 2017

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The structural evolution and phase-change kinetics of NiO-doped ZnSb films are investigated. NiO-doped ZnSb films exhibit a single-step crystallization process, which is different from that of undoped ZnSb. NiO-doped ZnSb can directly crystallize into a stable ZnSb phase at temperatures greater than 320 °C with suppression of a metastable ZnSb phase. These characteristics enlarge the amorphous/crystalline resistance ratio by approximately five orders of magnitude. Moreover, NiO doping of ZnSb films increases crystallization temperature from 260 to 275 °C, improves data retention temperature from 201.7 to 217.3 °C and increases crystalline activation energy from 5.64 to 6.34 eV. The improvement of the thermal parameters in the nanocomposite can be attributed to stable ZnSb grain growth refinement owing to the dispersion of NiO particles in the sample matrix. This provides additional nucleation sites and produces more ZnSb/NiO interfaces, which can initiate the nucleation and accelerate crystallization. The kinetic exponent n decreases from 1.12 to 0.44, which confirms the ultrafast one-dimensional growth and heterogeneous phase transition of the NiO-doped ZnSb films. The improved thermal stability, larger resistance ratio and direct transition to a stable phase with ultrafast one-dimensional crystal growth indicate the good potential of these materials in phase-change memory applications.

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Phase‐Change Memory Materials by Design: A Strain Engineering Approach

Cited by 133 publications

References 53 publications

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

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

Suppression for an intermediate phase in ZnSb films by NiO-doping

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Phase‐Change Memory Materials by Design: A Strain Engineering Approach

Cited by 133 publications

References 53 publications

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

Atomic Layering, Intermixing and Switching Mechanism in Ge-Sb-Te based Chalcogenide Superlattices

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

Suppression for an intermediate phase in ZnSb films by NiO-doping

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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