Germanium, antimony, tellurium, their binary and ternary alloys and the impact of nitrogen: An X-ray photoelectron study

Nolot, Emmanuel; Sabbione, C.; Pessoa, W.; Pražáková, Lucie; Navarro, G.

doi:10.1016/j.apsusc.2020.147703

Cited by 48 publications

(40 citation statements)

References 60 publications

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“…Thu have been able to detect only the presence of antimony oxide (Sb 3+ ), which is in accord with the hypothesis of Sb2O3 nanoparticles decoration of the graphene matrix, and no ing by Sb can be supported. Moreover, both the absence of a component in the r 529.1-529.6 eV and a peak at 396.7 eV (in the N1s region, see Figure 2b), which is monly attributed to SbN bond [27], let us confirm also the absence of a direct bon tween Sb and N.…”

Section: Xps Analysissupporting

confidence: 64%

Microwave-Assisted Synthesis of Nitrogen and Sulphur Doped Graphene Decorated with Antimony Oxide: An Effective Catalyst for Oxygen Reduction Reaction

et al. 2021

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In this study, we report on the facile synthesis of a novel electrocatalysts for the oxygen reduction reaction (ORR), based on reduced graphene oxide (RGO), functionalized with metallic and non-metallic elements. In particular, thanks to a fast one-pot microwave-assisted procedure, we induced, in the RGO graphene lattice, a combined doping with nitrogen and sulphur, and the simultaneous decoration with antimony oxide nanocrystals. The multi-doped–decorated material shows enhanced catalytic performance towards ORR, with respect to common nitrogen- or sulphur-doped carbon-based materials. The presence of co-doping is confirmed by transmission electron microscopy and X-ray photoelectron spectroscopy analysis. The detailed electrochemical characterization shows the simultaneous effects of dopant atoms on the catalytic behavior. In particular, the importance of nitrogen and sulphur atoms in driving the oxygen absorption, together with the role of antimony in enhancing the electrochemical performance toward the ORR, are discussed.

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Section: Xps Analysissupporting

confidence: 64%

Microwave-Assisted Synthesis of Nitrogen and Sulphur Doped Graphene Decorated with Antimony Oxide: An Effective Catalyst for Oxygen Reduction Reaction

et al. 2021

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“…After deposition of GGST, chemical shifts of the Te 4d and Ge 3d core levels toward higher BEs were clearly visible in the XPS spectra of both the heterostructures, while the opposite trend could be observed for Sb 4d ( Figure 2 b,c). To understand the behavior of the chemical shifts after the deposition of the GGST layers, it is useful to consider the expected BE shifts after the formation of binary compounds [ 21 , 22 , 23 ]. The Sb-Te bonding shifts the Sb 4d core levels toward higher BE (+0.6 eV with respect to metallic Sb) and the Te 4d toward lower BE (−0.55 eV with respect to metallic Te).…”

Section: Resultsmentioning

confidence: 99%

“…The Sb-Te bonding shifts the Sb 4d core levels toward higher BE (+0.6 eV with respect to metallic Sb) and the Te 4d toward lower BE (−0.55 eV with respect to metallic Te). Conversely, the Ge-Te bonding moves the Te 4d core levels of around 0.3 eV towards lower BE and the Ge 3d core levels to higher BE with a shift of +0.55 eV [ 21 , 22 , 23 ]. Therefore, after the formation of a ternary Ge-Sb-Te alloy, the BE of Te 4d core levels should be in the middle between the values expected for metallic Te and Sb 2 Te 3 .…”

Section: Resultsmentioning

confidence: 99%

Interface Formation during the Growth of Phase Change Material Heterostructures Based on Ge-Rich Ge-Sb-Te Alloys

et al. 2022

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In this study, we present a full characterization of the electronic properties of phase change material (PCM) double-layered heterostructures deposited on silicon substrates. Thin films of amorphous Ge-rich Ge-Sb-Te (GGST) alloys were grown by physical vapor deposition on Sb2Te3 and on Ge2Sb2Te5 layers. The two heterostructures were characterized in situ by X-ray and ultraviolet photoemission spectroscopies (XPS and UPS) during the formation of the interface between the first and the second layer (top GGST film). The evolution of the composition across the heterostructure interface and information on interdiffusion were obtained. We found that, for both cases, the final composition of the GGST layer was close to Ge2SbTe2 (GST212), which is a thermodynamically favorable off-stoichiometry GeSbTe alloy in the Sb-GeTe pseudobinary of the ternary phase diagram. Density functional theory calculations allowed us to calculate the density of states for the valence band of the amorphous phase of GST212, which was in good agreement with the experimental valence bands measured in situ by UPS. The same heterostructures were characterized by X-ray diffraction as a function of the annealing temperature. Differences in the crystallization process are discussed on the basis of the photoemission results.

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“…Incorporating impurities into GST225 induced higher crystallization temperature, better structural and thermal stability, and faster switching [ 8 , 14 ]. Interestingly, among all doping impurities, nitrogen doping is by far the most attractive and results in promising experimental works in the field [ 15 , 16 , 17 , 18 , 19 , 20 ]. Another approach is to deviate in composition from the stable GST225 phase by incorporating excess Ge, creating Ge-rich GST alloys.…”

Section: Introductionmentioning

confidence: 99%

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

et al. 2022

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Integration of the prototypical GeSbTe (GST) ternary alloys, especially on the GeTe-Sb2Te3 tie-line, into non-volatile memory and nanophotonic devices is a relatively mature field of study. Nevertheless, the search for the next best active material with outstanding properties is still ongoing. This search is relatively crucial for embedded memory applications where the crystallization temperature of the active material has to be higher to surpass the soldering threshold. Increasing the Ge content in the GST alloys seems promising due to the associated higher crystallization temperatures. However, homogeneous Ge-rich GST in the as-deposited condition is thermodynamically unstable, and phase separation upon annealing is unavoidable. This phase separation reduces endurance and is detrimental in fully integrating the alloys into active memory devices. This work investigated the phase separation of Ge-rich GST alloys, specifically Ge5Sb2Te3 or GST523, into multiple (meta)stable phases at different length scales in melt-quenched bulk and annealed thin film. Electron microscopy-based techniques were used in our work for chemical mapping and elemental composition analysis to show the formation of multiple phases. Our results show the formation of alloys such as GST213 and GST324 in all length scales. Furthermore, the alloy compositions and the observed phase separation pathways agree to a large extent with theoretical results from density functional theory calculations.

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Germanium, antimony, tellurium, their binary and ternary alloys and the impact of nitrogen: An X-ray photoelectron study

Cited by 48 publications

References 60 publications

Microwave-Assisted Synthesis of Nitrogen and Sulphur Doped Graphene Decorated with Antimony Oxide: An Effective Catalyst for Oxygen Reduction Reaction

Microwave-Assisted Synthesis of Nitrogen and Sulphur Doped Graphene Decorated with Antimony Oxide: An Effective Catalyst for Oxygen Reduction Reaction

Interface Formation during the Growth of Phase Change Material Heterostructures Based on Ge-Rich Ge-Sb-Te Alloys

Phase Separation in Ge-Rich GeSbTe at Different Length Scales: Melt-Quenched Bulk versus Annealed Thin Films

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