A Review on Disorder-Driven Metal–Insulator Transition in Crystalline Vacancy-Rich GeSbTe Phase-Change Materials

Wang, Jiangjing; Xu, Yazhi; Mazzarello, Riccardo; Wuttig, Matthias; Zhang, Wei

doi:10.3390/ma10080862

Cited by 58 publications

(26 citation statements)

References 128 publications

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“…with disordered vacancies possess insulating behavior. [60][61][62] Thus, control of disorder in phase change materials is very important for the application. Therefore, it is essential to reveal the local structure of relevant phases of the alloys.…”

Section: Introductionmentioning

confidence: 99%

Phase change thin films for non-volatile memory applications

2019

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Section: Introductionmentioning

confidence: 99%

Phase change thin films for non-volatile memory applications

2019

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“…The prototypical PCM material Ge 2 Sb 2 Te 5 (GST) has been intensively studied in the past a few years 4–6 . A lot of work have been done for the understanding of carrier transport due to its great importance for the crystalline state of PCM 7 . It has been reported that metal-insulator transition (MIT) upon annealing can be observed in crystalline GeSbTe compounds, and the Anderson localization resulted from the vacancy disorder is responsible for this MIT 8–10 .…”

Section: Introductionmentioning

confidence: 99%

Observation of carrier localization in cubic crystalline Ge2Sb2Te5 by field effect measurement

Qian

Tong

et al. 2018

Sci Rep

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The tunable disorder of vacancies upon annealing is an important character of crystalline phase-change material Ge2Sb2Te5 (GST). A variety of resistance states caused by different degrees of disorder can lead to the development of multilevel memory devices, which could bring a revolution to the memory industry by significantly increasing the storage density and inspiring the neuromorphic computing. This work focuses on the study of disorder-induced carrier localization which could result in multiple resistance levels of crystalline GST. To analyze the effect of carrier localization on multiple resistant levels, the intrinsic field effect (the change in surface conductance with an applied transverse electric field) of crystalline GST was measured, in which GST films were annealed at different temperatures. The field effect measurement is an important complement to conventional transport measurement techniques. The field effect mobility was acquired and showed temperature activation, a hallmark of carrier localization. Based on the relationship between field effect mobility and annealing temperature, we demonstrate that the annealing shifts the mobility edge towards the valence-band edge, delocalizing more carriers. The insight of carrier transport in multilevel crystalline states is of fundamental relevance for the development of multilevel phase change data storage.

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“…The transmission contrast in the NIR region between the amorphous phase and the crystalline phase and the rapid reversibility of Ge-Sb-Te alloys [42] can be used to design a reversible NIR transmission window [12]. It is clear from Figs.…”

Section: Resultsmentioning

confidence: 99%

Reduction of Rocksalt Phase in Ag -Doped Ge2Sb2Te5 : A Potential Material for Reversible Near-Infrared Window

Singh

Sharma

et al. 2018

Phys. Rev. Applied

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Phase-change materials are attracting much attention in the scientific and engineering communities owing to their applications and underlying basic phenomena. Ge 2 Sb 2 Te 5 is reversible-phase-change material (amorphous to crystalline and vice versa) that is used for optical data storage and phase-change random-access memory and has recently been explored for use as a reversible near-infrared (NIR) window [Singh et al., Appl. Phys. Lett. 111, 261102 (2017)]. For a reversible NIR window, large transmission contrast between two phases and low phase-transition temperature are required to reduce the power consumption. In the present work, phase transition in thermally deposited (Ge 2 Sb 2 Te 5) 100−x Ag x (x = 0, 1, 3, 5, and 10) thin films is achieved by vacuum thermal annealing. Transmission sharply decreases with phase transition in the NIR region. Ge 2 Sb 2 Te 5 shows large transmission contrast (more than 50%) in the wavelength range from 1600 to 3200 nm with phase transition from an amorphous to a hexagonal-closepacked structure at 260 • C. In (Ge 2 Sb 2 Te 5) 90 Ag 10 thin films, a similar transmission contrast is achieved at a comparatively lower temperature (160 • C) due to reduction of the rocksalt phase. Distortion of the host lattice with addition of 10% Ag is confirmed from the drastic change in the density of states in the valence band and the shift in core-level (3d) spectra of Ag, Sb, and Te. This distortion enables a hexagonal-closepacked phase in (Ge 2 Sb 2 Te 5) 90 Ag 10 thin films to be obtained at 160 • C. (Ge 2 Sb 2 Te 5) 90 Ag 10 could be a potential candidate for a reversible NIR window as it requires less power to achieve phase transition and high transmission contrast.

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A Review on Disorder-Driven Metal–Insulator Transition in Crystalline Vacancy-Rich GeSbTe Phase-Change Materials

Cited by 58 publications

References 128 publications

Phase change thin films for non-volatile memory applications

Phase change thin films for non-volatile memory applications

Observation of carrier localization in cubic crystalline Ge2Sb2Te5 by field effect measurement

Reduction of Rocksalt Phase in Ag -Doped Ge2Sb2Te5 : A Potential Material for Reversible Near-Infrared Window

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