Hydrothermal improvement for 3R-CuFeO2 delafossite growth by control of mineralizer and reaction atmosphere

Roble, M.; Rojas, S.; Wheatley, Robert; Wallentowitz, S.; Cabrera, A. L.; Díaz-Droguett, D.E.

doi:10.1016/j.jssc.2019.01.014

Cited by 20 publications

(12 citation statements)

References 65 publications

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“…The scattering peaks of these Ni-doped CuCrO 2 films are observed at about 100 cm –1 (E u ), 209 cm –1 (A g ), 456 cm –1 (E g ), and 707 cm –1 (A 1g ) as shown in Figure a, which agree well with previous results of delafossite structure . The Raman peaks at 456 cm –1 are assigned to the E g (O–Cr–O bending) vibrational modes, and the result is similar to the reported CuFeO 2 . Besides, the peaks at around 576 cm –1 are probably caused by defects like interstitial oxygen atoms or Cu vacancies .…”

Section: Results and Discussionsupporting

confidence: 80%

“…34 The Raman peaks at 456 cm −1 are assigned to the E g (O−Cr−O bending) vibrational modes, and the result is similar to the reported CuFeO 2 . 35 Besides, the peaks at around 576 cm −1 are probably caused by defects like interstitial oxygen atoms or Cu vacancies. 36 The A 1g mode represents the vibrations of Cu− O bonds along the c-axis.…”

Section: Resultsmentioning

confidence: 99%

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Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr_1–xNi_xO₂ Semiconductor Films

Zhang

Han

et al. 2021

J. Phys. Chem. C

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The transparent conductive CuCr 1−x Ni x O 2 (0 ≤ x ≤ 8%) films were prepared by sol−gel method with two-step annealing process. The structure, morphology, phonon modes, chemical composition, optical bandgap, and electrical properties were systematically studied. It was found that the crystal quality improves first and then decreases with increasing the Ni content, and the inflection point occurs when the doping content is 2% and all samples have the (00l) preferred orientation. In the visible region, the transmittances of these samples range from 75% to 55% as the Ni dopant increases. On the basis of the theoretical calculation, we are inclined to the view that there are two ways of coexisting electronic transitions. The direct band gap decreases from 3.13 to 3.02 eV, and the indirect band gap decreases from 2.78 to 2.49 eV with increasing Ni content. Transmittance spectra of the CuCrO 2 film at the temperatures from 323 to 453 K present the fact that the absorption edge shows a slight redshift, which is due to the lattice thermal expansion and the electron−phonon interaction. Raman spectroscopy shows that Ni doping can substitute the Cr sites and further affect Cu−O bonds, which is caused by oxygen deficiency or a relatively smaller crystallite size. Moreover, it suggested that the nonlinear temperature dependence of phonon frequency and line width is a sign of nonharmonic lattice dynamics. The inherent anharmonic force from the crystal results in energy exchange between harmonic phonon normal modes, thereby promoting thermal balance, and in the lattice. The Cu cations have been confirmed to exist in the valence state of Cu 1+ , and all doped Ni cations exist in a positive divalent state by XPS. Hall effect measurement shows that the conductivities and carrier concentrations of the doped CuCr 1−x Ni x O 2 films can be improved by several orders of magnitude larger than that of undoped CuCrO 2 . The present work suggests that these well crystallized films without a secondary phase can be applied in future p-type optoelectronic devices.

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Section: Results and Discussionsupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr_1–xNi_xO₂ Semiconductor Films

Zhang

Han

et al. 2021

J. Phys. Chem. C

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“…These substances are termed “mineralizers”. Mineralizers are generally a class of compounds whose solubility in water continues to increase with increasing temperature, such as some low melting salts, acids, and bases [47,48,49,50]. The addition of a suitable mineralizer not only increases the solubility of the solute in the hydrothermal solution, but also changes its solubility temperature coefficient.…”

Section: Hydrothermal Methodsmentioning

confidence: 99%

Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review

2019

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With the continuous development and progress of materials science, increasingly more attention has been paid to the new technology of powder synthesis and material preparation. The hydrothermal method is a promising liquid phase preparation technology that has developed rapidly during recent years. It is widely used in many fields, such as the piezoelectric, ferroelectric, ceramic powder, and oxide film fields. The hydrothermal method has resulted in many new methods during the long-term research process, such as adding other force fields to the hydrothermal condition reaction system. These force fields mainly include direct current, electric, magnetic (autoclaves composed of non-ferroelectric materials), and microwave fields. Among them, the microwave hydrothermal method, as an extension of the hydrothermal reaction, cleverly uses the microwave temperature to compensate for the lack of temperature in the hydrothermal method, allowing better practical application. This paper reviews the development of the hydrothermal and microwave hydrothermal methods, introduces their reaction mechanisms, and focuses on the practical application of the two methods.

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“…Our result is similar to that of previous UV-Vis absorption spectrum analyses and theoretical calculations. [18][19][20] To conrm that the CuFeO 2 single crystal is a direct band gap material, Fig. S4 † presents the room temperature photoluminescence spectrum of CuFeO 2 determined using a 325 nm excitation laser.…”

Section: B Electronic Excitationsmentioning

confidence: 99%

“…They reported that both the E g and A 1g modes exhibited a softening within 1 cm −1 below 14 K, which was associated with a pseudo-proper ferroelastic transition occurring in multiferroic materials. Wheatley et al 19 prepared CuFeO 2 thin films with thickness of 21 nm and 75 nm through pulse laser deposition. Using transmittance and diffuse reflectance spectra, they found a direct band gap of approximately 1.3 to 1.4 eV at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Temperature-dependent optical properties of CuFeO₂ through the structural phase transition

et al. 2021

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Hydrothermal improvement for 3R-CuFeO2 delafossite growth by control of mineralizer and reaction atmosphere

Cited by 20 publications

References 65 publications

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr_1–xNi_xO₂ Semiconductor Films

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr_1–xNi_xO₂ Semiconductor Films

Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review

Temperature-dependent optical properties of CuFeO₂ through the structural phase transition

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Hydrothermal improvement for 3R-CuFeO2 delafossite growth by control of mineralizer and reaction atmosphere

Cited by 20 publications

References 65 publications

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr1–xNixO2 Semiconductor Films

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr1–xNixO2 Semiconductor Films

Conventional and Microwave Hydrothermal Synthesis and Application of Functional Materials: A Review

Temperature-dependent optical properties of CuFeO2 through the structural phase transition

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Product

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Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr_1–xNi_xO₂ Semiconductor Films

Structural, Electronic Band Transition and Optoelectronic Properties of p-Type Transparent Conductive CuCr_1–xNi_xO₂ Semiconductor Films

Temperature-dependent optical properties of CuFeO₂ through the structural phase transition