Modulation of phase change characteristics in Ag-incorporated Ge2Sb2Te5 owing to changes in structural distortion and bond strength

Han, Jeong Hwa; Jeong, Kwang Sik; Ahn, Min Cheol; Lim, Dong Hyeok; Yang, Won Jun; Park, Seung Jong; Cho, Mann Ho

doi:10.1039/c6tc05412a

Cited by 23 publications

(20 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The other type is a very fast process of recovery to the original state within about 100 nsec. A typical example is the volatile switching found in filament-based selectors [17][18][19]. Our study of the middle rate of reversible variation may contribute to a unified understanding of these reversible changes.…”

Section: Introductionmentioning

confidence: 86%

“…The recovery time of 3-7 min at room temperature, which is much shorter than 75 h in an Ag/Ge 30 Se 70 device, can be attributed to the characteristics of Ag in Te-based chalcogenides and the smallness of the structural variations that cause the resistance variation. In Ag-GeTe 8 , and Ag-Ge 2 Sb 2 Te 5 , Ag diffusion and dissolution were facilitated by non-bonded Te anions [17,18] and longer Ag-Te bonds than other bonds [19]. In addition, the insulator-metal transition from amorphous to amorphous, as predicted by first-principles calculations of (GeSe 3 ) 1 − x Ag x [25], may contribute to the resistance variation.…”

Section: Mechanism Of Slow Reversible Resistance Variationmentioning

confidence: 96%

“…After illumination, the metastable system approached an equilibrium to segregate excess Ag and was dissolved by annealing due to increased solubility. The third one is the volatile resistance switching reported in Ag-Ge 2 Sb 2 Te 5 and Ag-GeTe 8 [17][18][19], which is applied to selectors in a crosspoint memory array. An external voltage bias application induced electrodeposition of Ag-rich conductive filaments, and no voltage application dissolved the filaments to return to the original state.…”

Section: Mechanism Of Slow Reversible Resistance Variationmentioning

confidence: 99%

See 2 more Smart Citations

Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride

et al. 2020

View full text Add to dashboard Cite

We report on the irreversible and reversible resistance changes for γ-ray irradiation in amorphous GeTe thin films with Ag electrodes. The γ-ray irradiation at a dose of 1 kGy irreversibly decreased the DC resistance by two orders of magnitude. The irreversible resistance change was caused by the formation of a conductive region that consisted of Ag-Te compounds. In-situ real-time DC resistance and AC impedance measurements revealed reversible variations in several electrode structures with DC resistances ranging widely from about 10 kΩ to about 5 MΩ. The DC resistance decreased by 2-5% with a time constant of about 3-7 min following the γ-ray irradiation with a dose rate of 0.5-2 kGy/h, and recovered on interruption. The AC impedance measurement was analyzed with a simple equivalent circuit consisting of a parallel RC circuit of the Ag-diffused GeTe matrix, connected serially to the interface resistance. The interface resistance and the capacitance of the matrix exhibited a fast reversible variation, which is explained by trapping and detrapping of carriers in the charged defects formed by the Ag re-diffusion. The resistance of the matrix showed a slow reversible variation with a time constant of 7 min, similar to the DC resistance. The slow reversible variation is attributed to the growth and dissolution of the conductive region caused by the Ag re-diffusion.

show abstract

Section: Introductionmentioning

confidence: 86%

Section: Mechanism Of Slow Reversible Resistance Variationmentioning

confidence: 96%

Section: Mechanism Of Slow Reversible Resistance Variationmentioning

confidence: 99%

See 1 more Smart Citation

Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The electrochemical reaction of Ag in amorphous chalcogenides of solid electrolytes has been investigated intensively because of the fundamental interests in anomalous diffusion [1], modified phase change characteristics [2,3], and optical properties [4][5][6] and also because of the potential device applications [7] such as RAM memories, sensors, and batteries. For example, the operation of conductive bridge RAM (CBRAM) devices [8,9] is based on the formation of conductive filaments via the electrochemical reaction of Ag ions.…”

Section: Introductionmentioning

confidence: 99%

Single-crystalline Ag2Te nanorods prepared by room temperature sputtering of GeTe

Nakaya

Nakaoka

2020

SN Appl. Sci.

View full text Add to dashboard Cite

We report a facile, single-crystalline Ag 2 Te nanorod formation based on electrochemical diffusion of Ag. The nanorods were grown non-epitaxially by sputtering deposition of GeTe on Ag 2 Te nanoparticles at room temperature. For the nanorod growth, the source of the Ag supply is not deposition but the diffusion of Ag from the nanoparticles. The growth of the single-crystalline Ag 2 Te nanorods required GeTe deposition onto Ag 2 Te nanoparticles, in contrast to the growth of amorphous Ag 2 Te nanorods caused by Te deposition onto Ag nanoparticles and the growth of other nanostructures caused by GeTe deposition on Ag nanoparticles. The GeTe deposition onto the Ag 2 Te nanoparticles of an amount equivalent to a 100-nm-thick film produced nanorods of a length ranging from 3 to 5 μm and a diameter ranging from 100 to 400 nm. We propose a model for the nanorod growth based on solid-state electrochemical reaction between GeTe and movable Ag ions, inducing nanoscale phase separation and precipitation of amorphous Ge. We suggest that the nanorod structure with a crystalline Ag 2 Te core and an amorphous Ge shell is useful for thermoelectric applications.

show abstract

“…Carbon-doped GST is a promising material for lowpower PCM applications because of its high resistivity and low thermal conductivity, which enable lower reset power compared with GST [16]. Irrespective of the preparation of samples, Ag addition is reported to significantly increase the speed of phase transition in GST thin films [17][18][19][20].…”

Section: Introductionmentioning

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

View full text Add to dashboard Cite

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.

show abstract

Modulation of phase change characteristics in Ag-incorporated Ge₂Sb₂Te₅ owing to changes in structural distortion and bond strength

Abstract: Ag-Incorporated Ge2Sb2Te5 (AGST) crystallizes faster and at a lower temperature than Ge2Sb2Te5 (GST) owing to the changes in local structure and chemical bonding.

Cited by 23 publications

References 35 publications

Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride

Reversible and irreversible resistance changes for gamma-ray irradiation in silver-diffused germanium telluride

Single-crystalline Ag2Te nanorods prepared by room temperature sputtering of GeTe

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

Contact Info

Product

Resources

About