Scanning tunneling microscopy and spectroscopy of the phase change alloy Ge1Sb2Te4

Subramaniam, Dinesh; Pauly, Christian; Liebmann, Marcus; Woda, Michael; Rausch, Pascal; Merkelbach, P.; Wuttig, Matthias; Morgenstern, Markus

doi:10.1063/1.3211991

Cited by 16 publications

(20 citation statements)

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“…4(a) that the interface is terminated by Te atoms and Ge atoms preferably occupy the sub-interface layer. This is in good agreement with other experimental 25 and theoretical calculation results, 26 which shows that Ge-terminated surface has much higher energy than the Te-terminated one. Large -Te-Gerings are formed by the terminated Te atoms and the Ge atoms in the sub-interface layer.…”

Section: B Insupporting

confidence: 92%

Structure and phonon behavior of crystalline GeTe ultrathin film

Tong

Miao

2014

Applied Physics Letters

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We report the drastic effect of film thickness on the structure and corresponding phonon behavior of crystalline GeTe ultrathin film. GeTe film with film thickness at ∼5 nm still shows good crystallization behavior and this highly scaled dimension confined almost all the crystallites to have preferred [111] orientation. The large specific interface area in ultrathin film give rise to the increase of tetrahedral coordinated Ge atoms and a rising Raman mode at low frequency is observed. These findings give implications for the thermal and electrical characters of phase change ultrathin films and thus for relevant scaling properties of Phase Change Memory.

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Section: B Insupporting

confidence: 92%

Structure and phonon behavior of crystalline GeTe ultrathin film

Tong

Miao

2014

Applied Physics Letters

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“…In addition, the electronic gap might be (slightly) exceeded by the optical gap due to the Burstein–Moss‐shift 37. Also in surface experiments, namely scanning tunneling spectroscopy, the shift of the Fermi‐level is observed 85. Low‐temperature Hall measurements have been conducted by Lee et al37 The Hall‐coefficient confirmed p‐type conduction in the crystalline phase, and did not exhibit a freeze‐out of carriers down to 5 K. Thus, for the investigated samples, the Fermi‐level must have been within the valence band.…”

Section: Materials Propertiesmentioning

confidence: 99%

Design Rules for Phase‐Change Materials in Data Storage Applications

2011

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Phase-change materials can rapidly and reversibly be switched between an amorphous and a crystalline phase. Since both phases are characterized by very different optical and electrical properties, these materials can be employed for rewritable optical and electrical data storage. Hence, there are considerable efforts to identify suitable materials, and to optimize them with respect to specific applications. Design rules that can explain why the materials identified so far enable phase-change based devices would hence be very beneficial. This article describes materials that have been successfully employed and dicusses common features regarding both typical structures and bonding mechanisms. It is shown that typical structural motifs and electronic properties can be found in the crystalline state that are indicative for resonant bonding, from which the employed contrast originates. The occurence of resonance is linked to the composition, thus providing a design rule for phase-change materials. This understanding helps to unravel characteristic properties such as electrical and thermal conductivity which are discussed in the subsequent section. Then, turning to the transition kinetics between the phases, the current understanding and modeling of the processes of amorphization and crystallization are discussed. Finally, present approaches for improved high-capacity optical discs and fast non-volatile electrical memories, that hold the potential to succeed present-day's Flash memory, are presented.

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“…The localization is lifted by annealing due to the respective continuous * Present address: Engineering Laboratory, University of Cambridge, Cambridge CB2 1PZ, United Kingdom † mmorgens@physik.rwth-aachen.de ordering of the Ge, Sb, and Vcs into different layers [18][19][20] . This is accompanied by a shift of the Fermi level E F towards the valence band (VB) 17,21 . However, the corresponding Fermi surface is not known as well as the exact position of E F , such that it is difficult to understand the electrical conductivity in detail.…”

Section: Introductionmentioning

confidence: 99%

Mapping the band structure of GeSbTe phase change alloys around the Fermi level

et al. 2018

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Phase change alloys are used for non-volatile random access memories exploiting the conductivity contrast between amorphous and metastable, crystalline phase. However, this contrast has never been directly related to the electronic band structure. Here, we employ photoelectron spectroscopy to map the relevant bands for metastable, epitaxial GeSbTe films. The constant energy surfaces of the valence band close to the Fermi level are hexagonal tubes with little dispersion perpendicular to the (111) surface. The electron density responsible for transport belongs to the tails of this bulk valence band, which is broadened by disorder, i.e., the Fermi level is 100 meV above the valence band maximum. This result is consistent with transport data of such films in terms of charge carrier density and scattering time. In addition, we find a state in the bulk band gap with linear dispersion, which might be of topological origin. arXiv:1708.08787v2 [cond-mat.mtrl-sci] 17 Jan 2018 AUTHOR CONTRIBUTIONS M.M. provided the idea of the experiment. J.K., M.L. and C.P. carried out all (S)ARPES experiments under the supervision of E

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Scanning tunneling microscopy and spectroscopy of the phase change alloy Ge1Sb2Te4

Cited by 16 publications

References 16 publications

Structure and phonon behavior of crystalline GeTe ultrathin film

Structure and phonon behavior of crystalline GeTe ultrathin film

Design Rules for Phase‐Change Materials in Data Storage Applications

Mapping the band structure of GeSbTe phase change alloys around the Fermi level

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