Nature of electrical resistivity and structural stability in N-doped GeTe models for reliable phase-change materials

Huang, Bolong

doi:10.1002/pssb.201451363

Cited by 11 publications

(4 citation statements)

References 33 publications

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“…, Overall, the typical crystallization temperature of these ALD films corresponds to the reported crystallization temperature of the sputtered GeTe film (180–190 °C). , The crystallization temperature is similar to that of the undoped GeTe despite the presence of the C and N impurities as observed in the AES. The impurities in this study exist without chemical bonding to the Ge or Te atoms as confirmed by XPS, which is distinguished from the previous cases where the impurities bind to the Ge atoms and increase the crystallization temperature. , …”

Section: Resultsmentioning

confidence: 54%

“…The impurities in this study exist without chemical bonding to the Ge or Te atoms as confirmed by XPS, which is distinguished from the previous cases where the impurities bind to the Ge atoms and increase the crystallization temperature. 32,33 Figure 10a shows the cross-sectional TEM image and composition mapping results using the EDS technique of the GeTe film deposited on a high-aspect-ratio hole structure at 170 °C. The opening diameter and depth of the holes was ∼100 and ∼2900 nm, respectively, giving rise to an aspect ratio of ∼29.…”

Section: Resultsmentioning

confidence: 99%

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Developing Precursor Chemistry for Atomic Layer Deposition of High-Density, Conformal GeTe Films for Phase-Change Memory

et al. 2019

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Atomic layer deposition (ALD) of phase-change materials has been suggested as the most feasible technique for the construction of high-aspect-ratio architectures required for ultrahigh-density phase-change random access memory (PcRAM). The recent advances in the ALD technique have established the foundations for the formation of conformal Ge–Te or Ge–Sb–Te films, but their electrical performance as a phase-change memory device has been rarely reported, especially with prolonged cycles. This study introduced Ge(II)–amido guanidinate (Ge(guan)NMe2 (guan = ( i PrN)2CNMe2, Me = CH3)) as a new ALD Ge precursor that was compatible with the high ALD temperature of up to 170 °C, which was necessary for achieving the high-density and stoichiometric as-deposited GeTe thin films. The films were deposited in an amorphous state. Coinjection of NH3 gas with the Te precursor (Te(SiMe3)2) was essential to initiate the feasible ALD reaction with the new Ge(II) precursor. Ab initio calculation proposed plausible exergonic chemical reaction pathways where NH3 actively participated in the dissociation of both −SiMe3 and guanidinate ligands from Te and Ge precursors, respectively. The ALD process showed self-limiting growth behavior and produced highly uniform and conformal morphologies. Low impurity levels (<5%) and a low crystallization temperature (180 °C) were observed for the samples deposited at 170 °C. The prototypical memory device showed a current–voltage curve with a voltage snapback region followed by switching to a low resistance state. Over 104 cycling endurance was achieved for the 170 °C grown GeTe film, whereas inferior endurance (<103) was observed for the low-temperature-grown GeTe.

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Section: Resultsmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 99%

Developing Precursor Chemistry for Atomic Layer Deposition of High-Density, Conformal GeTe Films for Phase-Change Memory

et al. 2019

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“…A weakness of the a-GeSe-type alloys as selectors is that their off-current is too high. This can be counteracted by alloying with N or C 43–49 as is well known previously. The addition of N or C both widens the band gap, reducing off-current, and also reduces atomic diffusion and nucleation rates, so raising the crystallization temperature.…”

Section: Calculationsmentioning

confidence: 92%

Materials Selection and Mechanism of Non-linear Conduction in Chalcogenide Selector Devices

Robertson

2019

Sci Rep

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The electronic structure and conduction mechanism of chalcogenide-based Ovonic threshold switches (OTS) used as selectors in cross-point memory arrays is derived from density functional calculations and quasi-Fermi level models. The switching mechanism in OTS is primarily electronic. This uses a specific electronic structure, with a wide tail of localized states below the conduction band edge. In amorphous GeSe2−x the conduction band consists of Ge-Se σ*states with a low effective mass, and with a broad tail of localized Ge-Ge σ* states below this band edge. This leads to the OTS behavior. At high fields the electron quasi-EF moves up through these tail states, lowering the conductivity activation energy, and giving the non-linear switching process. The 4:2 coordinated GeSe2−x based alloys are the most favorable OTS material because they have the correct network connectivity to give a high electron mobility and lack of crystallization, a favorable band structure to produce the non-linear conduction, an optimum band gap, and with nitrogen or carbon alloying, a sufficiently low off-current.

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“…A similar concept has been successfully utilized in other solid functional materials in our theoretical modeling. 34,[41][42][43] The key difference between UMPL materials and conventional PL materials is that the electrons and holes can be separated and allocated at the deep localized levels in the optical band gap area, due to the extra deep trap levels near the valence band maximum (VBM) and the extra hole traps near the conduction band maximum (CBM), as shown in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

Energy harvesting and conversion mechanisms for intrinsic upconverted mechano-persistent luminescence in CaZnOS

Huang

2016

Phys. Chem. Chem. Phys.

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We interpreted the mechanisms of energy harvesting and conversion for intrinsic upconverted mechano-persistent luminescence in CaZnOS through a native point defects study. We found that vacancy defects such as Zn and O vacancies, as well as Schottky pair defects, act as energy harvesting centers; they are very readily formed and very active. They are found to be extra deep electron or hole trap levels near the valence or conduction band edges, respectively. This leads to a coupling and exchange effect to continuously collect and transport host charges along a path via localized states to deep recombination levels. The initiating energy barrier is small and can be overcome by ambient thermal stimulation or quantum tunneling. Native activators such as V

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Nature of electrical resistivity and structural stability in N-doped GeTe models for reliable phase-change materials

Cited by 11 publications

References 33 publications

Developing Precursor Chemistry for Atomic Layer Deposition of High-Density, Conformal GeTe Films for Phase-Change Memory

Developing Precursor Chemistry for Atomic Layer Deposition of High-Density, Conformal GeTe Films for Phase-Change Memory

Materials Selection and Mechanism of Non-linear Conduction in Chalcogenide Selector Devices

Energy harvesting and conversion mechanisms for intrinsic upconverted mechano-persistent luminescence in CaZnOS

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