Refractive index spectral dependence, Raman spectra, and transmission spectra of high-purity 72Ge, 73Ge, 74Ge, 76Ge, and natGe single crystals

Lipskiy, V. A.; Nazaryants, V O; Kotereva, Т.V.; Буланов, А. Д.; Гавва, В. А.; Колташев, В. В.; Чурбанов, М. Ф.; Плотниченко, В. Г.

doi:10.1364/ao.58.007489

Cited by 5 publications

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“…Consequently, our Raman experiments confirm the presence of stress in our SLL films. One can see from Figure 6a that the vibration frequency of mode C (Ge-Ge bond) in the Ge layer of four SLL samples is always lower than one of Ge-Ge bonds in stress-free thick Ge film or crystalline Ge, implying the presence of tensile stress in the Ge layer [48,49]. The vibration frequencies of A and B modes in Ge 8 Sb 92 layers are always higher than the vibration frequencies, 111.6 and 150 cm −1 , of corresponding modes, respectively, in stress-free crystalline Sb, suggesting the existence of compressive stress in Ge 8 Sb 92 layers.…”

Section: Resultsmentioning

confidence: 98%

“…Hence A and B modes are assigned to the E g mode and A 1g of crystalline Sb in the Ge 8 Sb 92 layer, respectively. The vibration frequency of C mode increases monotonously with increasing x and approaches the vibration frequency (300 cm −1 ) of the Ge-Ge bond in 100 nm thick Ge film, and thereby, it is attributed to the vibration mode of Ge-Ge bonds [48]. The frequency shift of phonon modes with film thickness is a typical feature of stress effect, and is studied widely in various films [35,[43][44][45][46][47].…”

Section: Resultsmentioning

confidence: 98%

“…All Raman scattering spectra are plotted in Figure 4. One can see that the Raman spectra of four SLL samples [Ge 8 Sb 92 /Ge(x)] 3 present two stronger peaks at around 110 cm −1 (A) and 150 cm −1 (B) and a weaker broad band over a range of~200 cm −1 to 350 cm −1 where a weak peak appears near 280 cm −1 (C), while the Raman spectrum of the sole thick Ge film shows a single stronger peak at 300 cm −1 that might be attributed to the vibration of Ge-Ge bonds [48]. The Raman spectrum of 50 nm thick Ge 8 Sb 92 film is also plotted in Figure 4 for a contrast to the Raman spectra of four SLL films.…”

Section: Resultsmentioning

confidence: 99%

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Mechanism of Nano-Structuring Manipulation of the Crystallization Temperature of Superlattice-like [Ge8Sb92/Ge]3 Phase-Change Films

Qiu

et al. 2020

Nanomaterials

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Superlattice-like (SLL) phase-change film is considered to be a promising phase-change material because it provides more controllabilities for the optimization of multiple performances of phase-change films. However, the mechanism by which SLL structure affects the properties of phase-change films is not well-understood. Here, four SLL phase-change films [Ge8Sb92(15 nm)/Ge (x nm)]3 with different x are fabricated. Their behaviors of crystallization are investigated by measuring sheet resistance and coherent phonon spectroscopy, which show that the crystallization temperature (TC) of these films increases anomalously with x, rather than decreases as the interfacial effects model predicted. A new stress effect is proposed to explain the anomalous increase in TC with x. Raman spectroscopy reveals that Raman shifts of all phonon modes in SLL films deviate from their respective standard Raman shifts in stress-free crystalline films, confirming the presence of stress in SLL films. It is also shown that tensile and compressive stresses exist in Ge and Ge8Sb92 layers, respectively, which agrees with the lattice mismatch between the Ge and Ge8Sb92 constituent layers. It is also found that the stress reduces with increasing x. Such a thickness dependence of stress can be used to explain the increase in crystallization temperature of four SLL films with x according to stress-enhanced crystallization. Our results reveal a new mechanism to affect the crystallization behaviors of SLL phase-change films besides interfacial effect. Stress and interfacial effects actually coexist and compete in SLL films, which can be used to explain the reported anomalous change in crystallization temperature with the film thickness and cycle number of periods in SLL phase-change films.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

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Mechanism of Nano-Structuring Manipulation of the Crystallization Temperature of Superlattice-like [Ge8Sb92/Ge]3 Phase-Change Films

Qiu

et al. 2020

Nanomaterials

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“…Furthermore, there is an obvious red shift in peaks 1, 2, and 3 with increasing annealing temperature, which confirms the presence of tensile stress in the Ge-Cu-Te thin films; such tensile stress may originate from the thickness changes during the thermally-induced crystallization. [42][43][44][45][46][47] The surface oxidation and chemical bonding states of the asdeposited and annealed Ge-Cu-Te thin films are characterized by the XPS data obtained before and after Ar + ion sputtering (Fig. 6).…”

Section: Resultsmentioning

confidence: 99%

Elemental Redistribution During the Crystallization of Ge–Cu–Te Thin Films for Phase-Change Memory

Wang¹,

Chen²

2023

ECS J. Solid State Sci. Technol.

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Herein, a GeCu2Te2 alloy is proposed as a phase-change material for application in nonvolatile phase-change random access memory (PRAM). The crystallization kinetics and microchemical changes during phase transformation are investigated, and their correlation with the electrical behaviors of the GeCu2Te2 thin films are examined. The key findings are as follows: (ⅰ) the GeCu2Te2 alloy shows a higher crystallization temperature (~185°C) than the classic Ge2Sb2Te5 (GST) thin films, thus demonstrating superior thermal stability; (ⅱ) the crystallization kinetics demonstrate a decreasing in the Avrami exponent n from 4, which is related to the growth-dominated crystallization process evidenced by the micromorphology; (ⅲ) a massive redistribution of the chemical elements along the depth of the thin films during crystallization is considered to be driven by selective surface oxidation at amorphous state, and stress buildup during crystallization. In addition, the crystallization-induced stress is determined as ~168 MPa by utilizing the wafer curvature and X-ray diffraction methods for the GeCu2Te2 thin films. Finally, the lower threshold switching voltage ~1.72 V for amorphous GeCu2Te2 thin films is beneficial for reducing the SET operating power consumption. The authors believe that these results are valuable for the optimal phase change material design.

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“…Основное отличие заключается в соответствии полос поглощения соответствующей длине волны; наглядно видно, что изотопический состав кристаллов влияет на положение характерных полос поглощения Ge в рассматриваемом спектральном диапазоне. В спектральном диапазоне 11−40 µm нами выявлено 16 полос поглощения, что соответствует данным работ [38,39]; для изотопа 70 Ge положение характерных полос было выявлено впервые.…”

Section: экспериментальные результаты и обсуждениеunclassified

Изотопический Сдвиг ИК Полос Поглощения Монокристаллов Германия

Кропотов¹,

Рогалин²,

Каплунов³

et al. 2023

Оптика И Спектроскопия

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Refractive index spectral dependence, Raman spectra, and transmission spectra of high-purity ⁷²Ge, ⁷³Ge, ⁷⁴Ge, ⁷⁶Ge, and ^natGe single crystals

Cited by 5 publications

References 0 publications

Mechanism of Nano-Structuring Manipulation of the Crystallization Temperature of Superlattice-like [Ge8Sb92/Ge]3 Phase-Change Films

Mechanism of Nano-Structuring Manipulation of the Crystallization Temperature of Superlattice-like [Ge8Sb92/Ge]3 Phase-Change Films

Elemental Redistribution During the Crystallization of Ge–Cu–Te Thin Films for Phase-Change Memory

Изотопический Сдвиг ИК Полос Поглощения Монокристаллов Германия

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