Phase change thin films for non-volatile memory applications

Lotnyk, Andriy; Behrens, Mario; Rauschenbach, B.

doi:10.1039/c9na00366e

Cited by 108 publications

(73 citation statements)

References 143 publications

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“…However, the huge performance and density gaps between the working memory (DRAM) and the storage devices in the memory hierarchy lead to failure in meeting the massive data storage requirements. Phase-change memory (PCM) is an emerging high-density nonvolatile memory technology that might replace the current Si-based flash memory in the future 2 . PCM is based on the reversible switching between the amorphous and crystalline states of a phasechange material induced by either a laser or an electrical pulse, and such reversible switching is always associated with a large change in the resistance and optical reflectivity 3 .…”

Section: Introductionmentioning

confidence: 99%

Conversion of p–n conduction type by spinodal decomposition in Zn-Sb-Bi phase-change alloys

et al. 2020

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Phase-change films with multiple resistance levels are promising for increasing the storage density in phase-change memory technology. Diffusion-dominated Zn 2 Sb 3 films undergo transitions across three states, from high through intermediate to low resistance, upon annealing. The properties of the Zn 2 Sb 3 material can be further optimized by doping with Bi. Based on scanning transmission electron microscopy combined with electrical transport measurements, at a particular Bi concentration, the conduction of Zn-Sb-Bi compounds changes from p-to n-type, originating from spinodal decomposition. Simultaneously, the change in the temperature coefficient of resistivity shows a metal-toinsulator transition. Further analysis of microstructure characteristics reveals that the distribution of the Bi-Sb phase may be the origin of the driving force for the p-n conduction and metal-to-insulator transitions and therefore may provide us with another way to improve multilevel data storage. Moreover, the Bi doping promotes the thermoelectric properties of the studied alloys, leading to higher values of the power factor compared to known reported structures. The present study sheds valuable light on the spinodal decomposition process caused by Bi doping, which can also occur in a wide variety of chalcogenide-based phase-change materials. In addition, the study provides a new strategy for realizing novel p-n heterostructures for multilevel data storage and thermoelectric applications.

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Section: Introductionmentioning

confidence: 99%

Conversion of p–n conduction type by spinodal decomposition in Zn-Sb-Bi phase-change alloys

et al. 2020

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“…However, the subsequent ordering of the vacancies into vacancy layers gradually improves the structural order in the cation sublattice in the GST225 materials, which vanishes the localized states and causes a transition from an insulating to a metallic state. Unlike its electrical properties, the optical properties difference is likely due to the changes in the free carrier absorption caused by the electron localization effects [23], [38], [39]. As revealed from the corresponding electrical measurements, the vacancy order phase (the second phase) was found to have a slightly higher carrier concentration than the disordered phase (the first phase).…”

Section: Phase-change Materialsmentioning

confidence: 93%

“…The amorphous-to-crystalline phase transition, exemplified by GST225, in fact experiences several intermediate crystalline phases (i.e., metastable phase) and eventually reaches a stable state at higher temperature [23]. It is well known that the crystalline GST225 at its first metastable phase presents a rock-salt structure belonging to the cubic system [24], as illustrated in Figure 3(a).…”

Section: Phase-change Materialsmentioning

confidence: 99%

“…The unit cell is marked by a rectangle and the main structural motif of the motif of the GST225 phase is marked by an octahedron. Reprinted with permission from [23].…”

Section: Phase-change Materialsmentioning

confidence: 99%

“…Considerable efforts have therefore endeavored to the comprehending of the physical properties of the Chalcogenide based materials. Firstly, the cubic metastable phase of the Chalcogenide alloy can undergo several modification due to a large number of the structural vacancies following different distributions [23]. Such spatial distributions of the vacancies in the crystalline Chalcogenide lattices play an important role in determining the electronic properties of the crystalline PCMs.…”

Section: Outlooksmentioning

confidence: 99%

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Applications of Phase Change Materials in Electrical Regime From Conventional Storage Memory to Novel Neuromorphic Computing

Liu

Wang

2020

IEEE Access

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Phase-change materials, also well known as the Chalcogenide alloy, have received considerable attention during last two decades owing to its widespread applications in the field of the electrical storage market such as phase-change random access memory and phase-change probe memory. In addition to the storage devices, its unique electrical properties that can be dynamically tunable with respect to the electrical excitations lead to numerous novel applications represented by memristor and memristor-based neuromorphic electrical circuits. These emerging applications undoubtedly allows for a further exploitation of the potential of phase-change materials, and thus makes it advantageous over other storage medium like ferroelectric and magnetic materials. In order to help researchers understand the role of phase-change materials in these novel applications as well as their importance for citizen's daily life, a comprehensive review that not only covers the traditional storage applications, but also the applications on these exotic devices becomes imperative. In this review, the chemical structure of phase-change materials and their remarkable electrical properties are first reviewed, followed by an introduction of their applications on the storage fields. The physical principles of various emerging electrical devices using phase-change materials are subsequently overviewed in association with their state-of-the-art progress. The prospect of phase-change materials for the future non-volatile electrical applications that are yet to be unraveled is finally envisaged.

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Chemical Bonding in Chalcogenides: The Concept of Multicenter Hyperbonding

Lee

Elliott

2020

Advanced Materials

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A precise understanding of the chemical bonding in amorphous, and crystalline, chalcogenides is still lacking due to the complexity arising from the delocalization of bonding, and nonbonding, electrons. Although an increasing degree of electron delocalization for elements down a column of the periodic table is widely recognized, its influence on chemical-bonding interactions, and on consequent material properties, of chalcogenides has not been comprehensively understood. Here, we provide a chemical-bonding framework for understanding chalcogenides by studying prototypical telluride non-volatile-memory, 'phasechange' materials (PCMs), and related chalcogenide compounds, via density-functional-theory molecular-dynamics (DFT-MD) simulations. Identification of the presence of multi-centre 'hyperbonding' interactions elucidates not only the origin of various material properties and their contrast between amorphous and crystalline phases, but also the very similar chemicalbonding nature between crystalline and amorphous PCMs, in marked contrast to the existing viewpoint. This new perspective will help in designing chalcogenide materials for diverse applications from a fundamental chemical-bonding point of view.

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Phase change thin films for non-volatile memory applications

Abstract: The paper reviews materials science aspects of chalcogenide-based phase change thin films relevant for non-volatile memory applications.

Cited by 108 publications

References 143 publications

Conversion of p–n conduction type by spinodal decomposition in Zn-Sb-Bi phase-change alloys

Conversion of p–n conduction type by spinodal decomposition in Zn-Sb-Bi phase-change alloys

Applications of Phase Change Materials in Electrical Regime From Conventional Storage Memory to Novel Neuromorphic Computing

Chemical Bonding in Chalcogenides: The Concept of Multicenter Hyperbonding

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