Spectroscopic investigation on phase transitions for Ge2Sb2Te5 in a wide photon energy and high temperature region

Seo, Yuichi; Chung, J.-S.; Lee, Y.S.; Choi, Eunhee; Cheong, Byung‐ki

doi:10.1016/j.tsf.2011.12.043

Cited by 10 publications

(2 citation statements)

References 28 publications

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“…As can be seen, k increases with increasing annealing temperatures, i.e., with an increase in local order. This result is in agreement with the published data obtained by others 22 as well as with the simulations shown in Fig. 8(a) and demonstrates a strong effect of the degree of local order on optical properties which is also in line with the results obtained in Ref.…”

Section: Resultssupporting

confidence: 94%

Crystalline GeTe-based phase-change alloys: Disorder in order

et al. 2012

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Through the combined use of x-ray absorption and scattering experiments and ab initio simulations, we demonstrate that the metastable cubic phase of GeTe-based phase-change alloys, e.g. Ge 2 Sb 2 Te 5 , is significantly more disordered than is generally believed, with a large number of Ge atoms located off octahedral resonantly bonded sites. The stochastic off-octahedral locations of Ge atoms, that are invisible to Bragg diffraction probing the average structure, lead to disruption of the continuous resonance bonding network of the crystalline phase, resulting in localization of charge carriers. It is proposed that the degree of coherency of local rhombohedral displacements, that may be varied, e.g., by doping, can serve as means to control electrical properties of Ge-Sb-Te alloys.

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Section: Resultssupporting

confidence: 94%

Crystalline GeTe-based phase-change alloys: Disorder in order

et al. 2012

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“…The capability of SE to determine not only thicknesses but also both the real and imaginary parts of the dielectric function simultaneously has been utilized in many phase-transition studies in charge transfer solids ( T = 150 → 400 K), crystallization of amorphous Si , also in the presence of Al, annealing of Si, NiSi ( T = 623 → 1023 K), the switchable molecular solid RbMn[FeCN 6 ] ( T = 150 → 400 K), Ge 2 Sb 2 Te 5 phase changing material ( T = 293 → 623 K), relaxation in a-InGaZnO, and phase change in vanadium oxides. − S. Bin Anooz et al determined the phase transition in epitaxial NaNbO 3 films grown under tensile lattice strain on the (110) DyScO 3 substrate up to T = 823 K. The n is measured at an energy of 3.2 eV, i.e., near the band gap of 3.9 eV, to best observe variations with phase transitions and structural changes. At RT, monoclinic a1a2 ferroelectric phase with exclusive in-plane electrical polarization and at T = 523 → 573 K depicts a ferroelectric-to-ferroelectric phase transition.…”

Section: Investigation Of Processesmentioning

confidence: 99%

Real-Time Ellipsometry at High and Low Temperatures

Mukherjee

Petrik

2023

ACS Omega

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Among the many available real-time characterization methods, ellipsometry stands out with the combination of high sensitivity and high speed as well as nondestructive, spectroscopic, and complex modeling capabilities. The thicknesses of thin films such as the complex dielectric function can be determined simultaneously with precisions down to sub-nanometer and 10–4, respectively. Consequently, the first applications of high- and low-temperature real-time ellipsometry have been related to the monitoring of layer growth and the determination of optical properties of metals, semiconductors, and superconductors, dating back to the late 1960s. Ellipsometry has been ever since a steady alternative of nonpolarimetric spectroscopies in applications where quantitative information (e.g., thickness, crystallinity, porosity, band gap, absorption) is to be determined in complex layered structures. In this article the main applications and fields of research are reviewed.

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Optical response characteristics arising from delocalized electrons in phase change materials

Bai²,

Song

et al. 2013

Acta Materialia

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Spectroscopic investigation on phase transitions for Ge2Sb2Te5 in a wide photon energy and high temperature region

Cited by 10 publications

References 28 publications

Crystalline GeTe-based phase-change alloys: Disorder in order

Crystalline GeTe-based phase-change alloys: Disorder in order

Real-Time Ellipsometry at High and Low Temperatures

Optical response characteristics arising from delocalized electrons in phase change materials

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