Structural, electrical, and optical properties of CoxNi1-xO films grown by metalorganic chemical vapor deposition

Roffi, Teuku Muhammad; Uchida, K.; Nozaki, Satoshi

doi:10.1016/j.jcrysgro.2014.10.027

Cited by 11 publications

(4 citation statements)

References 22 publications

(26 reference statements)

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“…Also the peak shapes suggest substitutional incorporation of the elements. The presence of two separate NiO and CoO phases usually results in clearly visible shoulders in the reflections . Additionally, the broad signals indicate very small crystallite sizes, which were calculated for the different Co contents using the Scherrer equation from the most intensive (200) peak at ≈42° 2θ.…”

Section: Resultsmentioning

confidence: 99%

“…The solubility of Co in the NiO lattice is often limited to a maximum concentration. At Co contents beyond 10–25 at%, the oxides tend to form either physical mixtures containing additional phases or another stable oxide, the Co 3 O 4 spinel (Ni x Co 3− x O 4 if doped with Ni) . Several articles report the synthesis of rock salt type NiCoO 2 with 50 at% Co content, but not other possible compositions .…”

Section: Introductionmentioning

confidence: 99%

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Rock Salt Ni/Co Oxides with Unusual Nanoscale‐Stabilized Composition as Water Splitting Electrocatalysts

Fominykh

Tok

Zeller

et al. 2017

Adv Funct Materials

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The influence of nanoscale on the formation of metastable phases is an important aspect of nanostructuring that can lead to the discovery of unusual material compositions. Here, the synthesis, structural characterization, and electrochemical performance of Ni/Co mixed oxide nanocrystals in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is reported and the influence of nanoscaling on their composition and solubility range is investigated. Using a solvothermal synthesis in tert-butanol ultrasmall crystalline and highly dispersible Ni x Co 1−x O nanoparticles with rock salt type structure are obtained. The mixed oxides feature non-equilibrium phases with unusual miscibility in the whole composition range, which is attributed to a stabilizing effect of the nanoscale combined with kinetic control of particle formation. Substitutional incorporation of Co and Ni atoms into the rock salt lattice has a remarkable effect on the formal potentials of NiO oxidation that shift continuously to lower values with increasing Co content. This can be related to a monotonic reduction of the work function of (001) and (111)-oriented surfaces with an increase in Co content, as obtained from density functional theory (DFT+U) calculations. Furthermore, the electrocatalytic performance of the Ni x Co 1−x O nanoparticles in water splitting changes significantly. OER activity continuously increases with increasing Ni contents, while HER activity shows an opposite trend, increasing for higher Co contents. The high electrocatalytic activity and tunable performance of the nonequilibrium Ni x Co 1−x O nanoparticles in HER and OER demonstrate great potential in the design of electrocatalysts for overall water splitting.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rock Salt Ni/Co Oxides with Unusual Nanoscale‐Stabilized Composition as Water Splitting Electrocatalysts

Fominykh

Tok

Zeller

et al. 2017

Adv Funct Materials

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“…For this, the electronic structure (unoccupied states of the conduction band) of the samples has been investigated using XANES measurement at the O K-edge (1 s absorption). T. M. Roffi et al,53 has reported the variation of optical gap for Co doped NiO thin lms from 3.7 eV to 2.35 eV for the variation of x from 0 to 0.35. The change in optical gap is 1.35 eV which is larger than the change in the gap of 0.35 eV as observed in the present work for the same variation of x.…”

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confidence: 99%

Structural, optical and electronic properties of Ni_1−xCo_xO in the complete composition range

et al. 2020

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“…This result is further confirmed by our ellipsometry measurements; see below. The transmittance of non-stoichiometric Co x Ni 1−x O films was investigated by Roffi et al [42]. Accordingly, the measured transmittance decreases with increasing cobalt content x, while the absorption edge moves to longer wavelengths (smaller photon energies).…”

Section: Optical Propertiesmentioning

confidence: 99%

Crystalline Structure and Optical Properties of Cobalt Nickel Oxide Thin Films Deposited with a Pulsed Hollow-Cathode Discharge in an Ar+O2 Gas Mixture

Kapran,

Hippler,

Wulff

et al. 2024

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Cobalt nickel oxide films are deposited on Si(111) or fluorine-doped tin-oxide-coated (FTO) glass substrates employing a pulsed hollow-cathode discharge. The hollow cathode is operated with argon gas flowing through the nozzle and with O2 gas admitted to the vacuum chamber. Three different cathode compositions (Co20Ni80, Co50Ni50, and Co80Ni20) are investigated. Deposited and annealed thin films are characterized by X-ray diffraction, infrared (Raman) spectroscopy, and ellipsometry. As-deposited films consist of a single mixed cobalt nickel oxide phase. Upon annealing at 600 °C, the mixed cobalt nickel oxide phase separates into two cystalline sub-phases which consist of cubic NiO and cubic Co3O4. Annealed films are investigated by spectroscopic ellipsometry and the optical bandgaps are determined.

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Structural, electrical, and optical properties of CoxNi1-xO films grown by metalorganic chemical vapor deposition

Cited by 11 publications

References 22 publications

Rock Salt Ni/Co Oxides with Unusual Nanoscale‐Stabilized Composition as Water Splitting Electrocatalysts

Rock Salt Ni/Co Oxides with Unusual Nanoscale‐Stabilized Composition as Water Splitting Electrocatalysts

Structural, optical and electronic properties of Ni_1−xCo_xO in the complete composition range

Crystalline Structure and Optical Properties of Cobalt Nickel Oxide Thin Films Deposited with a Pulsed Hollow-Cathode Discharge in an Ar+O2 Gas Mixture

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Structural, electrical, and optical properties of CoxNi1-xO films grown by metalorganic chemical vapor deposition

Cited by 11 publications

References 22 publications

Rock Salt Ni/Co Oxides with Unusual Nanoscale‐Stabilized Composition as Water Splitting Electrocatalysts

Rock Salt Ni/Co Oxides with Unusual Nanoscale‐Stabilized Composition as Water Splitting Electrocatalysts

Structural, optical and electronic properties of Ni1−xCoxO in the complete composition range

Crystalline Structure and Optical Properties of Cobalt Nickel Oxide Thin Films Deposited with a Pulsed Hollow-Cathode Discharge in an Ar+O2 Gas Mixture

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Structural, optical and electronic properties of Ni_1−xCo_xO in the complete composition range