Direct observation of amorphous to crystalline phase transitions in nanoparticle arrays of phase change materials

Raoux, Simone; Rettner, Charles; Jordan-Sweet, Jean; Kellock, A. J.; Topuria, Teya; Rice, Philip M.; Miller, Dolores C.

doi:10.1063/1.2801000

Cited by 102 publications

(71 citation statements)

References 13 publications

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“…9 Widespread use of phase change technologies that operate via differential resistivity, however, still relies critically on optimizing material parameters that govern the speed, cyclability, and power consumption of devices. 7,10, 11 Many technologically relevant phase-change materials are located on the ternary Ge-Sb-Te phase diagram, including alloys along the pseudobinary GeTe-Sb 2 Te 3 tie line, Ge 15 Te 85 , and doped Sb 2 Te. 11 Recent synthetic routes to these materials have largely focused on sputter deposition and lithographical patterning of phase-change films.…”

Section: Introductionmentioning

confidence: 99%

Liquid-Phase Synthesis of Uniform Cube-Shaped GeTe Microcrystals

2010

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Many Ge-based chalcogenide alloys, including GeTe, exhibit a reversible amorphous-to-crystalline phase change that is the basis for a wide range of current and next-generation technologies. Solution routes are attractive alternative strategies for synthesizing these materials, because they have the potential to impart morphology control on the crystallites and permit liquid-based processing of films and patterned structures. This paper describes a liquid-phase route to crystalline rhombohedral GeTe crystallites with cube-shaped morphologies and edge lengths of 1.0 ( 0.2 μm. The microcrystallites can be deposited onto planar substrates to produce highly textured (002) oriented films. During TEM imaging, the particles undergo electron beam induced fragmentation and, in some cases, partial amorphization. The GeTe crystallites are characterized by XRD, SEM, EDS (including element mapping), DSC, TEM, and electron diffraction.

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Section: Introductionmentioning

confidence: 99%

Liquid-Phase Synthesis of Uniform Cube-Shaped GeTe Microcrystals

2010

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“…The dimensionality of these systems ranges from thin films [9] to nanowires [13] and to nanoparticles [14]. Diameters of phase change nanowires previously synthesized range between 200 nm to 20 nm and depend on the size of the catalyst particle.…”

Section: Introductionmentioning

confidence: 99%

GeTe-filled Carbon Nanotubes for Data Storage Applications

et al. 2010

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By virtue of their unique electronic properties, nanometer-diameter sized single-walled carbon nanotubes represent ideal candidates to function as active parts of nanoelectronic memory storage devices. We show for the first time that GeTe, a phase change material, currently considered to be one of the most promising materials for data-storage applications, can efficiently be encapsulated within single-walled carbon nanontubes of 1.4 nm diameter. Structural investigations on the encapsulated GeTe nanowires have been carried out by high resolution transmission electron microscopy. The electronic interactions between the filling material and the host nanotube have been examined using ultraviolet photoelectron spectroscopy experiments and show that the electronic structure of the encapsulating nanotube and that of the encased filling are not perturbed by the presence of each of the other component. The newly formed hybrids offer potential to operate as active elements in non-volatile electronic memory storage devices.

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“…Following the original work of Ovshinsky 1 , the reversible switching phenomena observed in disordered semiconductors has attracted substantial theoretical 2,3,4,5,6,7 and experimental 8,9,10,11,12,13 efforts targeted at gaining a deep understanding of the physical principles that govern the switching dynamics, and also learning how to control and optimize the power requirements coupled with characteristic switching timescales. Dramatic and ultra-fast (nanosecond scale) changes in the physical properties such as electrical resistivity and optical reflectivity upon amorphization or crystallization makes chalcogenides ideal potential candidates for a universal non-volatile memory device, especially if, the device switching characteristics are highly scalable to nanometer dimensions.…”

Section: Introductionmentioning

confidence: 99%

Electrical switching dynamics in circular and rectangular Ge2Sb2Te5 nanopillar phase change memory devices

Ozatay

Stipe

Katine

et al. 2008

Journal of Applied Physics

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We have measured the critical phase change conditions induced by electrical pulses in Ge 2 Sb 2 Te 5 nanopillar phase change memory devices by constructing a comprehensive resistance map as a function of pulse parameters (width, amplitude and trailing edge). Our measurements reveal that the heating scheme and the details of the contact geometry play the dominant role in determining the final phase composition of the device such that a non-uniform heating scheme using rectangular contacts promotes partial amorphization/crystallization for a wide range of pulse parameters enabling multiple resistance levels for data storage applications. Furthermore we find that fluctuations in the snap-back voltage and set/reset resistances in repeated switching experiments are related to the details of the current distribution such that a uniform current injection geometry (i.e. circular contact) favors more reproducible switching parameters. This shows that possible geometrical defects in nanoscale phase change memory devices may play an essential role in the performance of the smallest possible devices through modification of the exact current distribution in the active chalcogenide layer. We present a three-dimensional finite element model of the electro-thermal physics to provide insights into the underlying physical mechanisms of the switching dynamics as well as to quantitatively account for the scaling behaviour of the switching currents in both circular and rectangular contact geometries. The calculated temporal evolution of the heat distribution within the pulse duration shows distinct features in rectangular contacts providing evidence for locally hot spots at the sharp corners of the current injection site due to current crowding effects leading to the observed behaviour.

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Direct observation of amorphous to crystalline phase transitions in nanoparticle arrays of phase change materials

Cited by 102 publications

References 13 publications

Liquid-Phase Synthesis of Uniform Cube-Shaped GeTe Microcrystals

Liquid-Phase Synthesis of Uniform Cube-Shaped GeTe Microcrystals

GeTe-filled Carbon Nanotubes for Data Storage Applications

Electrical switching dynamics in circular and rectangular Ge2Sb2Te5 nanopillar phase change memory devices

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