Recrystallization of an amorphized epitaxial phase-change alloy: A phoenix arising from the ashes

Rodenbach, Peter; Giussani, A.; Perumal, K.; Hanke, Michael; Dubslaff, M.; Riechert, H.; Calarco, Raffaella; Burghammer, Manfred; Kolobov, A. V.; Fons, Paul

doi:10.1063/1.4742919

Cited by 18 publications

(13 citation statements)

References 12 publications

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“…9 Thus, we assert that the crystalline substrate acts as a template for the crystallizing GST film in the cubic phase, since they share the same out-of-plane orientation [111]Si jj [111]GST. This feature was also reported by Rodenbach et al 18 for laser amorphized and recrystallized GST, epitaxially grown on crystalline substrates. This furthermore shows the technological relevance of GST alloys produced by MBE.…”

Section: Resultssupporting

confidence: 83%

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Structural change upon annealing of amorphous GeSbTe grown on Si(111)

Bragaglia

Jenichen

Giussani

et al. 2014

Journal of Applied Physics

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The structural change upon annealing of an amorphous GeSbTe (GST) film deposited by molecular beam epitaxy on a Si(111) substrate is studied by means of X-ray diffraction (XRD), X-ray reflectivity (XRR), and atomic force microscopy (AFM). XRD profiles reveal that both metastable cubic and stable hexagonal phases are obtained with a single out-of-plane orientation. XRR study shows a density increase and consequent thickness decrease upon annealing, in accordance with literature. From both, the XRD and the AFM study, it emerges that the crystalline substrate acts as a template for the film, favoring the crystallization of the amorphous GST into the [111] oriented metastable cubic phase, and the latter turns into the [0001] stable hexagonal phase for higher annealing temperature. V

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Section: Resultssupporting

confidence: 83%

“…Analysis of the XRR curves indicates a decrease in thickness and increase in the GST density with increasing annealing temperatures, in agreement with previous studies. 22,23 This enforces previous evidence 18 that the MBE produced material is consistent with the one deposited by PVD.…”

Section: Discussionsupporting

confidence: 87%

Structural change upon annealing of amorphous GeSbTe grown on Si(111)

Bragaglia

Jenichen

Giussani

et al. 2014

Journal of Applied Physics

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“…It is worth noting that a recent work reports re-crystallization from a meltquenched state back into the initial epitaxial state by not more than ten femtosecond laser pulses at low fluence. 20 The authors attribute this astonishing ability to either a latent memory of the amorphous phase of its original state or the single crystalline interface being crucial for nucleation and growth.…”

Section: Resultsmentioning

confidence: 99%

Stimulated crystallization of melt-quenched Ge2Sb2Te5 films employing femtosecond laser double pulses

Cotton

Siegel

2012

Journal of Applied Physics

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The phase transformation of Ge 2 Sb 2 Te 5 films from the melt-quenched amorphous phase into the crystalline phase induced by 800 nm, 100 fs laser pulses has been studied. For partly amorphized films, progressive crystallization could be induced by single pulses, which can be explained by growth of already existing crystalline embryos. For completely amorphized films, it was not possible to induce crystallization with one or two consecutive pulses; three pulses being the threshold for the onset of crystallization. By employing a fs laser double pulse with an adjustable inter-pulse delay, partial crystallization could be triggered for a delay range of 200 fs-100 ps, while for longer delays no crystallization was possible. The time window for stimulated crystallization can be related to the relaxation dynamics of free electrons excited by the first pulse, which are further excited by the second pulse still remaining in the excited state. Our results indicate that the lifetime of excited electrons in melt-quenched amorphous Ge 2 Sb 2 Te 5 is %100 ps. V C 2012 American Institute of Physics. [http://dx.

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“…By selective excitation of the A 1 phonon mode, an iPCM sample was permanently transformed into the SET state with an average temperature rise of less than 10 • C (fluence of 0.1 mJ/cm 2 ) [7]. In addition, femtosecond optical switching experiments on epitaxial films have also suggested alternative athermal crystallization processes may be present when ultrafast optical irradiation is used [8]. These observations serve as motivation for the direct study of atom displacement in ultrafast laser-induced coherent phonon excitation.…”

Section: Introductionmentioning

confidence: 99%

Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

et al. 2014

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Coherent phonons (CPs) generated by laser pulses on the femtosecond scale have been proposed as a means to achieve ultrafast, nonthermal switching in phase-change materials such as Ge 2 Sb 2 Te 5 (GST). Here we use ultrafast optical pump pulses to induce coherent acoustic phonons and stroboscopically measure the corresponding lattice distortions in GST using 100-ps x-ray pulses from the European Synchrotron Radiation Facility (ESRF) storage ring. A linear-chain model provides a good description of the observed changes in the diffraction signal; however, the magnitudes of the measured shifts are too large to be explained by thermal effects alone, implying the presence of excited-state effects in addition to temperature-driven expansion. The information on the movement of atoms during the excitation process can lead to greater insight into the possibilities of using CP-induced phase transitions in GST.

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Recrystallization of an amorphized epitaxial phase-change alloy: A phoenix arising from the ashes

Cited by 18 publications

References 12 publications

Structural change upon annealing of amorphous GeSbTe grown on Si(111)

Structural change upon annealing of amorphous GeSbTe grown on Si(111)

Stimulated crystallization of melt-quenched Ge2Sb2Te5 films employing femtosecond laser double pulses

Picosecond strain dynamics inGe2Sb2Te5monitored by time-resolved x-ray diffraction

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