Band gap widening with time induced by structural relaxation in amorphous Ge2Sb2Te5 films

Fantini, Paolo; Brazzelli, S.; Cazzini, Elena; Mani, Antonio

doi:10.1063/1.3674311

Cited by 66 publications

(59 citation statements)

References 28 publications

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“…Our measurements of thick films enable the determination of the absorption coefficient over a large energy range. They confirm that, on aging, the band gap indeed increases, consistent with previous PDS 44 and ellipsometry data 43 . In addition, the PDS data in Fig.…”

Section: Resultssupporting

confidence: 80%

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Aging mechanisms in amorphous phase-change materials

et al. 2015

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Aging is a ubiquitous phenomenon in glasses. In the case of phase-change materials, it leads to a drift in the electrical resistance, which hinders the development of ultrahigh density storage devices. Here we elucidate the aging process in amorphous GeTe, a prototypical phase-change material, by advanced numerical simulations, photothermal deflection spectroscopy and impedance spectroscopy experiments. We show that aging is accompanied by a progressive change of the local chemical order towards the crystalline one. Yet, the glass evolves towards a covalent amorphous network with increasing Peierls distortion, whose structural and electronic properties drift away from those of the resonantly bonded crystal. This behaviour sets phase-change materials apart from conventional glass-forming systems, which display the same local structure and bonding in both phases.

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Section: Resultssupporting

confidence: 80%

“…The findings reported so far immediately raise the question how the properties of the amorphous state will change upon structural relaxation. From experiments, the optical band gap has been shown to widen on aging 43 . We have calculated the energy gap as a function of Ge T concentration (shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Aging mechanisms in amorphous phase-change materials

et al. 2015

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“…Up to this point, all theoretical models [12,14,25,29,[50][51][52], while strongly differing in the underlying physical mechanisms, predict an increase in activation energy over time. At the same time, none of these models deals with a potential change in the Arrhenius prefactor yet.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, it is known that the optical bandgap of thin films of amorphous phase change material opens while the resistance drifts [13,14]. Also, a change of thermopower with time has been measured on thin films of amorphous phase change materials [15].…”

Section: Introductionmentioning

confidence: 99%

Role of activation energy in resistance drift of amorphous phase change materials

et al. 2014

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The time evolution of the resistance of amorphous thin films of the phase change materials Ge 2 Sb 2 Te 5 , GeTe and AgIn-Sb 2 Te is measured during annealing at T = 80 • C. The annealing process is interrupted by several fast temperature dips to determine the changing temperature dependence of the resistance. This procedure enables us to identify to what extent the resistance increase over time can be traced back to an increase in activation energy E A or to a rise of the prefactor R * . We observe that, depending on the material, the dominating contribution to the increase in resistance during annealing can be either a change in activation energy (Ge 2 Sb 2 Te 5 ) or a change in prefactor (AgIn-Sb 2 Te). In the case of GeTe, both contribute about equally. We conclude that any phenomenological model for the resistance drift in amorphous phase change materials that is based on the increase of one parameter alone (e.g., the activation energy) cannot claim general validity.

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“…Currently, Ge 2 Sb 2 Te 5 (GST) films are the best chalcogenide material for PCM and have received sustained attention [7][8][9][10][11]. In PCM, the data writing/erasing process is achieved by using the heat generated by a laser pulse or an electric pulse to induce phase transitions between an amorphous phase and a polycrystalline phase in the GST films.…”

Section: Introductionmentioning

confidence: 99%