Crystallization times of Ge–Te phase change materials as a function of composition

Raoux, Simone; Cheng, Huai-Yu; Caldwell, Marissa A.; Wong, H.-S. Philip

doi:10.1063/1.3212732

Cited by 123 publications

(65 citation statements)

References 6 publications

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“…According to the recent study in Ref. 20, it can be expected that crystallization upon single laser pulse irradiation can be achieved only with pulses >30 ns. In order to achieve crystallization with shorter pulses, additional optimization of the heat-flow conditions is required.…”

Section: Quantification Of the Optical Contrastmentioning

confidence: 99%

“…17,18 GeTe in particular has received increasing industrial interest as an active material in electrical PCMs, especially in nonvolatile memory devices. 19 Recently, Raoux et al 20 reported an extensive study on crystallization times in GeTe films produced via rf sputtering as a function of alloy composition. They confirmed earlier reports, by Chen et al, 5 that crystallization times for compositions other than the stoichiometric one increase by orders of magnitude, and they underlined the role played by the melt-quenched amorphous phase in the fast re-crystallization process.…”

Section: Introductionmentioning

confidence: 99%

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Dynamics of laser-induced phase switching in GeTe films

Gawełda

Siegel

Afonso

et al. 2011

Journal of Applied Physics

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High Seebeck effects from conducting polymer: Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) based thin-film device with hybrid metal/polymer/metal architecture APL: Org. Electron. Photonics 5, 238 (2012) High Seebeck effects from conducting polymer: Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) based thin-film device with hybrid metal/polymer/metal architecture Appl. Phys. Lett. 101, 173304 (2012) Response to "Comment on 'Silver/silicon dioxide/silver sandwich films in the blue-to-red spectral regime with negative-real refractive index'" [Appl. Phys. Lett. 101, 156101 (2012)] Appl. Phys. Lett. 101, 156102 (2012) On the determination of the glass forming ability of AlxZr1−x alloys using molecular dynamics, Monte Carlo simulations, and classical thermodynamics J. Appl. Phys. 112, 073508 (2012) Enhanced photoanode properties of epitaxial Ti doped α-Fe2O3 (0001) thin films Appl. Phys. Lett. 101, 133908 (2012) Additional information on J. Appl. Phys. Phase switching in GeTe thin films (grown using a modified metal organic chemical vapor deposition system) upon pulsed femtosecond and nanosecond laser irradiation has been studied. Two in situ methods, i.e., optical microscopy and real-time reflectivity measurements, have been used in order to compare the optical response before and after phase change and to follow the phase change dynamics with a time resolution close to 400 ps. The results show that cycling is possible under irradiation with both fs and ns pulses using single pulses for amorphization and multiple pulses for crystallization. The use of ns pulses favors the crystalline-to-amorphous phase transformation, with a characteristic transformation time of $15 ns. The presence of the liquid phase was identified and temporally resolved, featuring a well-defined transient reflectivity state, in between those of the crystalline and amorphous phases. We have also studied the role of material configuration in the phase change dynamics and the mechanisms involved in the re-crystallization process.

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Section: Quantification Of the Optical Contrastmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamics of laser-induced phase switching in GeTe films

Gawełda

Siegel

Afonso

et al. 2011

Journal of Applied Physics

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“…Earlier studies in the low-temperature regime have determined crystal growth velocities of as-deposited (AD) PCMs 10 and a comparison with growth velocities of melt-quenched (MQ) material 11 revealed a few hundred times higher rates in the MQ glassy state. Laser-driven experiments revealed that shorter pulses can induce crystallization in the MQ but not in the AD state 12,13 . However, approaches to study crystal growth velocities based on optical lasers or electrical excitation were limited to pulse lengths longer than a nanosecond and therefore could not determine growth velocities over the entire range of temperatures 11,[13][14][15][16] .…”

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confidence: 99%

How Supercooled Liquid Phase-Change Materials Crystallize: Snapshots after Femtosecond Optical Excitation

et al. 2015

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Glass forming materials are employed in information storage technologies making use of the transition between a disordered (amorphous) and an ordered (crystalline) state. With increasing temperature the crystal growth velocity of these phase-change materials becomes so fast that prior studies have not been able to resolve these crystallization dynamics. However, crystallization is the time limiting factor in the write speed of phase-change memory devices. Here, for the first time, we quantify crystal growth velocities up to the melting point by using the relaxation of photo-excited carriers as an ultrafast heating mechanism.During repetitive femtosecond optical excitation, each pulse enables dynamical evolution for tens of picoseconds before the intermediate atomic structure is frozen-in as the sample rapidly cools. We apply this technique to Ag 4 In 3 Sb 67 Te 26 (AIST) and compare the dynamics of as-deposited and application-relevant melt-quenched glass. Both glasses retain their different kinetics even in the supercooled liquid state, thereby revealing differences in their kinetic fragilities. This approach enables the characterization of application-relevant properties of phase-change materials up to the melting temperature, which has not been possible before.Mankind has utilized glasses during the last five thousand years. They can be prepared by cooling a liquid fast and far enough below the glass transition temperature -to a temperature where its viscosity is sufficiently high that the atomic arrangement is kinetically frozen-in 1 . Until recently, research and technology have focused on good glass formers, i.e. materials which can be vitrified by cooling their liquid state at moderate rates. But in recent decades poor glass formers such as metallic glasses and certain chalcogenide glasses have gained interest due to their remarkable property portfolio 2,3 . These materials need to be cooled at rates in excess of around 3*10 9 K/s to bypass crystallization and to quench the atoms in an amorphous arrangement 4 . This so-called glass transition at temperature is commonly observed at a

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“…The initial on-state resistance as-received from the integrated circuit foundry was 1.22 X, which, after about 20 pulses, settles in to a value of under 0.9 X. While GeTe has been shown to crystallize with a heat pulse as short as 30ns, 18 we find that a longer $1ls pulse produces the lowest resistance on-state. For the experiments reported here, we did neither monitor the NiCrSi's resistance nor the GeTe's resistance with time, and thus, the exact time required to switch off-to-on or on-to-off is not known.…”

mentioning

confidence: 79%