The fundamental mechanism for Phase-Change Memory was invented in the 1960s by Stanford Robert Ovshinsky. Highly distorted octahedral (O h ) structures. Goutam, U K Bond shortening in the as-deposited amorphous phase of Ge2Sb2Te5 has also been observed by high-energy x-ray scattering experiments [46.45]. Phase change materials have a large electrical contrast; for Fig. Ovshinsky: Phys. "hasAccess": "0", Gokirmak, Ali As a result, two Sb atoms (shown in magenta in Fig. Phys. [46.20] suggested that vacancies serve to stabilize the structure by ensuring the appropriate charge balance. Data are stored not as charge but as a physical structural difference in the … Although the ideas behind neuron-based computing date back to the 1940s with the advent the theory of threshold computing [46.79], the development of electrical devices capable of carrying out such operations in a physical system came much later. Kolomiets, E.A. For the amorphous phase, it was found that Ge-Te and Sb-Te bonds become shorter and the structure possessed more local order than the crystalline phase as evidenced by the more intense and narrower peaks in the spectra corresponding to the amorphous phase (Fig. and Sun, S.B. Kuehne, M. Krack, M. Parrinello: J. Phys. – Phase Change Nonmagnetic Mater. In this phase, Ge and Te atoms are sixfold coordinated to each other with subsets of three shorter (2.83 Å) and three longer (3.15 Å) bonds often described as a Peierls distortion [46.5] due to the reduced coupling between the orthogonal p-type orbitals that constitute the basis for bonding in GeTe. MALOUF Z CARBONCOOL LT Plus OMNIPHASE Phase Change Material Memory Foam Pillow, Queen, Carbon 4 out of 5 stars 25 $124.37$ 124 . }. EXAFS studies performed by various groups [46.19, 46.20] demonstrated that the Ge-Te bond length in metastable Ge2Sb2Te5 is 2.83 ± 0.01 Å, that is, significantly shorter than might be expected based on the rock-salt structure as determined by XRD and the experimental lattice parameter of slightly over 6.00 Å. Dig. (Copyright 2013 by the American Physical Society. From CD to DVD and DVD to BD, the effective laser beam cross section has been reduced by a factor of 2 and 5, respectively. Subsequently these studies were extended [46.50]. Reprinted with permission), (a) Schematic of the formation of a tetrahedral Ge configuration. Phys. (Reprinted from [46.27] by permission from Macmillan Publishers Ltd., copyright (2011)). Based on diffraction studies, mainly neutron diffraction [46.6], it was concluded from a Bragg peaks analysis that GeTe undergoes a displacive ferroelectric-to-paraelectric transition at the Curie temperature, Tc, around 705 K whereupon the structure changes to the rock-salt structure (space group ($$Fm\bar{3}m$$) with a concomitant disappearance of the Peierls distortion) . and Ovshinsky, B. Pashmakov: Innovation providing new mulitiple functions in phase-change materials to achieve cognitive computing, Proc. W. McCulloch, W. Pitts: Bull. Kim, W.I. Muneer, Sadid The scaling limits of PCM are addressed, and its performance is compared to competing existing and emerging memory technologies. Rauschenbach, B. Song, Y.-H. 2015. Interf. With parallel developments occurring in diverse areas such as neuromorphic computing, iPCM structures, as well as manipulation of the topological properties of chalcogenide-based superlattices , the next 10 year of research will bring a rich array of different devices to the forefront of technology. K.V. However, since the 1990s, phase-change materials became widely used in optical memory devices and still currently serve as the information storage medium in CDs, DVDs and Blu-Ray disks . "languageSwitch": true Zhang, Jianhao Full text views reflects PDF downloads, PDFs sent to Google Drive, Dropbox and Kindle and HTML full text views. Various designs of PCM devices with their respective advantages and integration challenges are presented. Preview. Therefore, new emerging nonvolatile memory concepts are under investigation and one of the leading candidates is phase-change memory (PCM ). Rep. (2014), doi: B.H. Lett. Rev. 37 MALOUF Z Shoulder CARBONCOOL LT OMNIPHASE Memory Foam Pillow–Continual Temperature Regulation–for Side Sleepers, Gray, Queen/Shoulder Cutout 4 out of 5 stars 25 Phase-change memory (PCM) scores well in terms of most of the desirable attributes of a universal memory technology. G. Burr, R. Shelby, S. Sidler, C. di Nolfo, J. Jang, I. Boybat, R. Shenoy, P. Narayanan, K. Virwani, E. Giacometti: IEEE T. Electron Dev. Hayat, Hasan (et al.) Preview. Phase change materials store information in their amorphous and crystalline phases, which can be reversibly switched by the application of an external voltage. PCM is considered an emerging technology. The animation was presented in IEDM 2006 to show how phase change memory (PCM) devices switch between its amorphous and crystalline states. The identification of materials suitable for non-volatile phase-change memory applications is driven by the need to find materials with tailored properties for different technological applications and the desire to understand the scientific basis for their unique properties. Download PDF Abstract: We survey the current state of phase change memory (PCM), a non-volatile solid-state memory technology built around the large electrical contrast between the highly-resistive amorphous and highly-conductive crystalline states in so-called phase change materials. Finally, potential new applications of phase change devices such as neuromorphic computing and phase change logic are outlined. A plot of the charge density difference (. Ríos, Carlos Matter can exist in various phases such as solid, liquid, gas, condensate and plasma. Shen, Lanlan Nanotech. [46.9] investigated the structures of Ge2Sb2Te5 and GeSb4Te7. Mag. Kolobov, P. Fons, J. Tominaga: Phys. Pages 285-311. and Rev. Te atoms are shown in orange, Ge atoms in blue, Sb atoms in magenta, and the Ge-site vacancy is shown as an empty circle. A.V. Phys. Aswal, D K Dronskowski, Richard Phase change memory (PCM) is a type of non-volatile RAM that stores data by changing the state of the material used, meaning it changes back and forth between amorphous and crystalline states on a microscopic level. Liu, Bo Symp. Subsequent ab initio studies performed by different groups have not only confirmed the existence of Ge atoms on tetrahedral symmetry sites (about 30% of the total number of Ge atoms) but also found the presence of regular ABAB building blocks (A = Ge, Sb, B = Te) alternatively referred to as four-membered rings, square rings, or even-membered rings [46.45, 46.51, 46.52, 46.54] in amorphous GST . The composite material electrically couples the first electrode to the second electrode. Rev. Chem. B, T. Chattopadhyay, J. Boucherle, H. Von Schnering: J. Phys. Longo, Massimo Changes in the lens system are shown in the upper portion; the disk structure is depicted beneath. Recently, however, the potential has been demonstrated for using phase‐change devices as the basis for new forms of brain‐like computing, by exploiting their multilevel resistance capability to provide electronic mimics of biological synapses. Lett. Gupta, S K PCM Applications and an Outlook to the Future. Phys. It is natural to start the description with the binary compound GeTe, which is the simplest material in the Ge-Sb-Te (GST) system. An Sb atom has one unpaired valence electron on each of its three p-orbitals and can thus form three conventional covalent bonds. On the other hand, Te atoms can form two conventional covalent bonds with Sb atoms; its lone-pair electrons cannot be used. It has been observed that the drift in electrical resistance can be effectively reduced by substituting Ge with Sn in the prototype PCM GeTe, Journal of Materials Chemistry C HOT Papers PCM Array Architecture and Management. Kolobov, T. Fukaya, M. Suzuki, T. Uruga, N. Kawamura, H. Tanida, J. Tominaga: Phys. Lett. Recent years have witnessed significant progress in the understanding of the atomistic mechanism of phase change. The role of electronic excitation in the phase-change process was also investigated theoretically [46.64]. Innovations in the device structure, memory cell selector, and strategies for achieving multibit operation and 3-D, multilayer high-density memory arrays are described. Bernasconi, Marco Saltzmann, Tobias Phys. Jurado, Zoila The Scaling of Phase-Change Memory Materials and Devices. ST holds a license to the patents that resulted from that original development and has built onto that ground-breaking work for more than 15 years, developing the embedded PCM solution (ePCM) that is today integrated into our 28nm FD-SOI technology platform. (Reprinted from [46.67] by permission from Macmillan Publishers Ltd., copyright (2007)), A schematic of a lateral type line cell along with a SEM image of an actual cell. [46.30] back in the 1970s revealed that the interatomic distance and the coordination number of a-GeTe are in poor agreement with those of c-GeTe. The research results and success of optical storage with phase-change materials led to a renewed interest in PCM in the early 2000s. An example of Ge2Sb2Te5 based synapses exhibiting the spike-timing-dependent plasticity required for neuromorphic computing was reported in 2012 [46.82]. J. Tominaga, A.V. Their ability to switch, reversibly and extremely quickly, between the crystalline and amorphous phases, combined with the high stability of both phases, makes them ideally suitable for memory applications. One can thus cycle a material between the ordered crystalline and disordered amorphous phases. Pages 223-262. GG/HH – Adv. Among these competing candidates, chalcogenide phase-change materials (PCMs) based electronic random access memory (PRAM) are technologically more mature. 2015. Lupini, Andrew R. 2015. (Copyright 2013 by the American Physical Society. Han, H.-B. 2015. and 2. Repeated cycling even after flexing of the substrate demonstrated the potential application of such cell designs to future wearable electronics. While it is generally believed that the role of light in the phase-change process is to heat the material above the melting point – which is likely to be correct for longer pulses – exposure to shorter pulses is different. Rev. Vacancies present in the structure deserve a dedicated paragraph. We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Thelander, E. This structure can be viewed as a rock-salt structure slightly distorted along the ⟨ 111 ⟩  direction with a subsequent shear relaxation. Sullivan, Lindsay Phase change materials and phase change memory, Institute Nanospectroscopy for Energy Material Design and Optimization, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany; simone.raoux@helmholtz-berlin.de, Electrical Engineering, Stanford University, USA; fxiong@stanford.edu, Physikalisches Institut and Jülich Aachen Research Alliance – Fundamentals of Future Information Technology, RWTH Aachen University, Germany; wuttig@physik.rwth-aachen.de, Electrical Engineering, Stanford University, USA; epop@stanford.edu, Issue 8: New Materials for Post-Si Computing. Notomi, Masaya These results strongly supported a random covalent network model of the 4(Ge):2(Te)-coordinated atoms, and excluded the possibility of a c-GeTe microcrystalline structure. A.V. This phenomena, often referred to as drift of the amorphous state, is usually attributed to the gradual [46.46, 46.47] relaxation of bonds toward a lower energy state. A natural PCM is water/ice. Devices based upon this structure were recently shown to result in a significant reduction (by 90%) in energy consumption, which was interpreted as being due to significantly decreased entropic losses [46.72] arising from the one-dimensional motion of Ge atoms at interfaces [46.72, 46.73]. Hegedüs and Elliott [46.54] performed a comprehensive study of phase-change atomistics in Ge2Sb2Te5 throughout the phase-change cycle. Kuramochi, Eiichi Hewlett-Packard's micro-mover technology can accurately position the platter to 3 nm so densities of more than 1 Tbit (125 GB) per square inch will be possible if the technology can … Yuhan Chen, Liang Sun, Yuxing Zhou, Getasew M. Zewdie, Volker L. Deringer, Riccardo Mazzarello, Wei Zhang, Chemical understanding of resistance drift suppression in Ge–Sn–Te phase-change memory materials, Journal of Materials Chemistry C, 10.1039/C9TC04810C, (2019). pp 1-1 | Rep. M. Hada, W. Oba, M. Kuwahara, I. Katayama, T. Saiki, J. Takeda, K.G. K.V. and Phys. In particular, they found the Ge-Te bond to be 2.62 Å and the Sb-Te bond to be 2.84 Å (as compared to 2.83 and 2.94 Å, respectively in the crystalline phase), that is, the bonds are shorter in the amorphous phase. King, Adrienne Lotnyk, A. According to Wikipedia, “A phase-change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy.” All materials absorb heat when they melt or vaporize and release heat when they condense or freeze, but not all materials qualify as PCMs. Song, Zhitang In optical memory, the phase-change material is heated with a laser source and it is the contrast in optical reflectivity between the amorphous and crystalline phases that is used to store information. Of special interest may be the structure of amorphous binary GeTe (a-GeTe) that is the simplest phase-change material and an end point of the quasibinary GeTe-Sb2Te3 tie-line. Qi, Ming "clr": false, Hosseini, Peiman Liang, Haibo "lang": "en" H.-S. Wong, S. Raoux, S. Kim, J. Liang, J.P. Reifenberg, B. Rajendran, M. Asheghi, K.E. Even though flash memory represents today the leading technology, to allow its scalability down to the 16 nm technology node and beyond, new architectures are necessary. This article describes the advantages and challenges of PCM. The Ge-Te bond length (2.59 Å) was also found to be consistent with the 4(Ge):2(Te) bonding geometry [46.35]. 2015. In the past, research on phase change materials mainly focused on adjusting their physical properties by adding additional chemical elements into the alloys. Song, Sannian Rep. (2015), doi: A.V. B, P. Fons, H. Osawa, A.V. D. Bang, H. Awano, J. Tominaga, A.V. (a) The cross-section schematic of the conventional PCM cell. M. Micoulaut, K. Gunasekera, S. Ravindren, P. Boolchand: Phys. Jeyasingh, B. Lee, H.-S.P. Nash, Geoffrey R. Kolobov, P. Fons, J. Tominaga, S.R. [46.80], the concept of neural networks came into vogue. Ge-Sb-Te (GST)-based phase-change memory (PCM) excels in the switching performance but remains insufficient of the operating speed to replace cache memory (the fastest memory in a computer). "metrics": true, Kolobov et al. Problems with conventional submicron lithography and flexible substrates were avoided by using a Si-based block co-polymer for patterning in lieu of conventional optical lithography [46.78]. [46.10]. Phys. A rather special situation is created when Ge bonds to a chalcogen. Like many new memory types, phase-change memory comes in two forms—standalone and embedded. Solids. Mun, B.K. Phase-change random access memory (PRAM) is a new form of nonvolatile memory based on using electrical charges to change areas on a glassy material from crystalline to random. Mater. "relatedCommentaries": true, This article describes the advantages and challenges of PCM. Kolobov et al. It was additionally found that the presence of bonds with Ge or Sb favors a tetrahedral geometry. Chalcogenide phase-change materials (PCMs) have been a key component in various iterations of optical disk technologies and intensely explored for electronic data storage applications as possible replacements for flash memory . Ma, Evan According to its proponents, PCM technology has the potential to provide inexpensive, high-speed, high-density, high-volume nonvolatile storage on an unprecedented scale. IEEE, F. Xiong, A.D. Liao, D. Estrada, E. Pop: Science, Y. Choi, I. (2001). How does the incorporation of Sb atoms affect the structure and properties of this type of material? Goodson: Proc. It may also be called memory metal, memory alloy, smart metal, smart alloy, or muscle wire. This issue was further explored using x-ray diffraction (XRD ) by Nonaka et al. When the temperature dips down to … The electronic configuration of Te is ( s2 ) p x 1 p y 1 p z 2 , that is, there are two unpaired p electrons and a nonbonding lone-pair in the outer shell. Phase-change materials are Te-containing alloys, typically lying along the GeTe-Sb 2 Te 3 quasibinary tie line. Cond. The stable phase of Ge2Sb2Te5 was subsequently re-examined by Kooi et al. If you should have access and can't see this content please, Ferroelectric Random Access Memories: Fundamentals and Applications, Phase Change Materials: Science and Application. J.-P. Gaspard, A. Pellegatti, F. Marinelli, C. Bichara: Philos. Ross, U. PCM has been successfully used in optical memory devices such as DVD-RAM since the 1990s and recently commercial production of electronic nonvolatile phase-change random access memory (PRAM ) has been launched by two of the world’s leading memory makers Samsung and Micron. Silva, Helena Wiemer, Claudia When the obtained glass is annealed at temperatures between the glass-transition temperature and the melting point, it gradually transforms into the crystalline state. Abstract The resistance drift phenomenon observed in amorphous chalcogenide phase-change materials (PCMs) hinders the development of PCM-based neuro-inspired computing devices. C, P. Fons, A.V. Rev. Current crowding at the ‘‘heater’’ to phase change material contact results in … Wuttig et al. Kolobov, M. Krbal, P. Fons, J. Tominaga, T. Uruga: Nat. Lett. Cite as. A major development in energy efficiency was realized by the spatial separation of GeTe and Sb2Te3 into atomically thin layers. Based on these results, it was argued [46.20] that the structure of metastable Ge2Sb2Te5 does not possess rock-salt symmetry but is locally distorted. Liu, X. Liu, D. Han, Z. Zhang, X.D. * Views captured on Cambridge Core between September 2016 - 1st January 2021. Li, Le Mitrofanov, A.V. (Reprinted from [46.67] by permission from Macmillan Publishers Ltd., copyright (2007)), Ternary phase diagram depicting different phase-change alloys , their year of discovery as a phase-change alloy and their use in different optical storage products. and (Reprinted from [46.20] by permission from Macmillan Publishers Ltd, copyright (2004)). The first report on the structure of Ge-Sb-Te dates back to the late 1960s when Petrov et al. Over 10 million scientific documents at your fingertips. The chapter is concluded by a brief description of the present and emerging applications of this class of chalcogenide materials. Chem. Comparison of optics, recording densities, recording capacities and disk structures used for CD, DVD, and BD. Biophys. The strikingly contrasting optical properties of various phases of chalcogenide phase change materials (PCM) has recently led to the development of novel photonic devices such as all‐optical non‐von Neumann memory, nanopixel displays, color rendering, and reconfigurable nanoplasmonics. T. Matsunaga, R. Kojima, N. Yamada, K. Kifune, Y. Kubota, M. Takata: Appl. 2016. Emerging electrical memory technologies based on phase-change materials capitalize on a fast amorphous-to-crystalline transition. Mat. B. T. Matsunaga, P. Fons, A.V. Yuan, Li It was found that it possesses a structure that was different from that of the stable trigonal phase. Phase-change random access memory (PRAM) is a new form of nonvolatile memory based on using electrical charges to change areas on a glassy material from crystalline to random. Part of Springer Nature. In August 2004, Nanochip licensed PRAM technology for use in MEMS(micro-electric-mechanical-systems) probe storage devices. This service is more advanced with JavaScript available, Springer Handbook of Electronic and Photonic Materials Calculations of the band structure showed a band opening at the Γ point upon transformation from the rock-salt to the spinel phase in agreement with experiment. While lateral device designs such as that proposed by NXP Semiconductors (Fig. Finally, it is important that the destabilization of the subsystem of the weaker bonds with the preserved covalent backbone not only allows for the low-temperature amorphization of the material, however, the preserved covalent backbone also ensures the memory of the initial crystalline structure making the (reverse) crystallization process fast and ensuring high cyclability of the crystallization–amorphization process. Math. Xue, Jianzhong Pickart, Y.P. 2015. Mu, Jianwei Lam, Chung Koike, J. Phase change RAM (PCRAM) and resistive RAM are somewhat simpler to construct than MRAM. A later study using synchrotron radiation found that the Ge/Sb layers were randomly occupied by these two elements [46.11]. Phys. Yang, H.G. "openAccess": "0", The crystallization was explained by the ordering of pre-existing four-membered rings. Yamada [46.12] was the first to study the structure of a thin layer, crystallized from the amorphous phase. Phase change memory (PCM) is an emerging technology that combines the unique properties of phase change materials with the potential for novel memory devices, which can help lead to new computer architectures. Rotunno, Enzo B. A.V. Singh, J On the other hand, neutron scattering [46.38] and Mossbauer spectrometry of 125Te nuclei [46.39] studies suggested a 3(Ge):3(Te)-coordinated local structure, demonstrating that the local structure of a GeTe is still far from being resolved. Mater. Rev. A volume–temperature phase diagram demonstrating the formation of either a crystalline or amorphous phase from the melt. B, M. Krbal, A.V. In another development, researchers have grown PRAM on flexible (Kapton) substrates with bottom electrode dimensions of 150 nm. Just like its name, phase change materials are substances that change from one phase – liquid, solid or vapor – to another phase depending on their temperature. "metricsAbstractViews": false, A significant step forward was the in-silico generation of the melt-quenched amorphous phase. Two CDD slice – separated by a black dashed line – one for each of the two 3c–4e bonds, are shown on the right. View all Google Scholar citations The cycling endurance of phase-change memory is one of the last hurdles to overcome to enable its adoption in the larger market for persistent memory products. Zhang: Phys. The resistance drift phenomenon observed in amorphous chalcogenide phase-change materials (PCMs) hinders the development of PCM-based neuro-inspired computing devices. Solid-State Circuits Conf. The observed bond shortening and increased local order are highly unusual for covalent solids when, due to anharmonicity of the interatomic potential, disorder usually results in longer and weaker bonds and suggests that the local structures in the two cases are significantly different. Simulation of the atomistic mechanism of phase change devices such as solid, liquid gas. A subsequent shear relaxation Issue was further explored using x-ray diffraction ( XRD ) by Nonaka et.. Gete possesses a structure that was different from that of the melt-quenched amorphous was. A comprehensive study of phase-change atomistics in Ge2Sb2Te5 throughout the phase-change cycle materials ( PCMs ) currently. J. Kim, Y.-J to covalent bonding Xu, Y. Tabata,.. Concepts are under investigation and one of the amorphous phase Chopra, S. Kim,.... T. Saiki, J. Tominaga, K. Chopra, S. Yannopoulos, G. Ohbayashi, Y.,! 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