Energy-Efficient Phase-Change Memory with Graphene as a Thermal Barrier

Ahn, Chang-Nam; Fong, Scott W.; Kim, Yongsung; Lee, Seunghyun; Sood, Aditya; Neumann, Christopher M.; Asheghi, Mehdi; Goodson, Kenneth E.; Pop, Eric; Wong, H.-S. Philip

doi:10.1021/acs.nanolett.5b02661

Cited by 133 publications

(88 citation statements)

References 41 publications

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“…For example, few‐layer graphene has been investigated as a potential floating gate (FG) material in future flash memories with the aim to reduce the leakage currents through the gate stack and minimize capacitive coupling interferences among neighboring cells (see Section ). The insertion of single‐layer graphene (SLG) in PCMs as a thermal resistance layer between the Ge–Sb–Te (GST) phase‐change material and the tungsten heater electrode has resulted in memory cells with improved energy efficiency compared to the reference devices . Graphene has also been widely used as ultrathin flexible/transparent electrode or as an interfacial layer in ReRAMs for lowering power consumption and for suppressing detrimental surface effects .…”

Section: Introductionmentioning

confidence: 99%

Nonvolatile Memories Based on Graphene and Related 2D Materials

et al. 2019

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The pervasiveness of information technologies is generating an impressive amount of data, which need to be accessed very quickly. Nonvolatile memories (NVMs) are making inroads into high‐capacity storage to replace hard disk drives, fuelling the expansion of the global storage memory market. As silicon‐based flash memories are approaching their fundamental limit, vertical stacking of multiple memory cell layers, innovative device concepts, and novel materials are being investigated. In this context, emerging 2D materials, such as graphene, transition metal dichalcogenides, and black phosphorous, offer a host of physical and chemical properties, which could both improve existing memory technologies and enable the next generation of low‐cost, flexible, and wearable storage devices. Herein, an overview of graphene and related 2D materials (GRMs) in different types of NVM cells is provided, including resistive random‐access, flash, magnetic and phase‐change memories. The physical and chemical mechanisms underlying the switching of GRM‐based memory devices studied in the last decade are discussed. Although at this stage most of the proof‐of‐concept devices investigated do not compete with state‐of‐the‐art devices, a number of promising technological advancements have emerged. Here, the most relevant material properties and device structures are analyzed, emphasizing opportunities and challenges toward the realization of practical NVM devices.

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Section: Introductionmentioning

confidence: 99%

Nonvolatile Memories Based on Graphene and Related 2D Materials

et al. 2019

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“…Graphene and carbon nanotubes (CNT) are extremely good heat conductors in-plane or along the tube axis [21,22], but the weak interactions between layers lead to low out-of-plane thermal conductivity [23,24]. Reduced heat loss from the PCM layer has been demonstrated recently with carbon nanotubes [25,26] and graphene [27], where low set and reset currents were attained, and 10 5 programming cycles were achieved with graphene as an electrode interface material [27]. The interaction between the PCM and the heater (such as TiN) also leads to degradation of PC-RAM [28,29], which could well be reduced by a graphene buffer between them.…”

Section: Introductionmentioning

confidence: 99%

Tuning electronic properties of graphene heterostructures by amorphous-to-crystalline phase transitions

2016

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The remarkable ability of phase change materials (PCM) to switch between amorphous and crystalline states on a nanosecond time scale could provide new opportunities for graphene engineering. We have used density functional calculations to investigate the structures and electronic properties of heterostructures of thin amorphous and crystalline films of the PCM GeTe (16Å thick) and Ge2Sb2Te5 (20Å) between graphene layers. The interaction between graphene and PCM is very weak, charge transfer is negligible, and the structures of the chalcogenide films differ little from those of bulk phases. A crystalline GeTe (111) layer induces a band gap opening of 80 meV at the Dirac point. This effect is absent for the amorphous film, but the Fermi energy shifts down along the Dirac cone by −60 meV. Ge2Sb2Te5 shows similar features, although inherent disorder in the crystalline rocksalt structure reduces the contrast in band structure from that in the amorphous structure. These features originate in charge polarization within the crystalline films, which show electromechanical response (piezoelectricity) upon compression, and show that the electronic properties of graphene structures can be tuned by inducing ultra-fast structural transitions within the chalcogenide layers. Graphene can also be used to manipulate the structural state of the PCM layer and its electronic and optical properties.

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“…Given that this is nominally a weak, van der Waals bonded interface, there are potential trade-offs in choosing layered heat spreaders. For example, a higher in-plane thermal conductivity might come at the cost of a lower interfacial thermal conductance [55], [56].…”

Section: Low-dimensional Materials: Anisotropic Heat Spreadersmentioning

confidence: 99%

The Heat Conduction Renaissance

Sood

Pop

Asheghi

et al. 2018

2018 17th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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Some of the most exciting recent advancements in heat conduction physics have been motivated, enabled, or achieved by the thermal management community that ITherm serves so effectively. In this paper we highlight the resulting renaissance in basic heat conduction research, which is linked to cooling challenges from power transistors to portables. Examples include phonon transport and scattering in nanotransistors, engineered high-conductivity composites, modulated conductivity through phase transitions, as well as the surprising transport properties of low-dimensional (1D and 2D) nanomaterials. This work benefits strongly from decades of collaboration and leadership from the semiconductor industry.

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Energy-Efficient Phase-Change Memory with Graphene as a Thermal Barrier

Cited by 133 publications

References 41 publications

Nonvolatile Memories Based on Graphene and Related 2D Materials

Nonvolatile Memories Based on Graphene and Related 2D Materials

Tuning electronic properties of graphene heterostructures by amorphous-to-crystalline phase transitions

The Heat Conduction Renaissance

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