Raman Spectroscopy of Nanocrystalline Ceria and Zirconia Thin Films

Kosacki, Igor; Petrovsky, Vladimir; Anderson, Harlan U.; Colomban, Philippe

doi:10.1111/j.1151-2916.2002.tb00509.x

Cited by 187 publications

(106 citation statements)

References 19 publications

(41 reference statements)

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“…While the peaks at about 600 cm −1 can be assigned to intrinsic V O (marked with Δ in Fig. 2), which is sensitive to any disorder in the oxygen sublattice resulting from thermal, doping, or grain size [22][23][24][25]. The intensity of intrinsic V O Raman active mode in Ce 1-x Fe x O 2 samples is pronounced than in pure CeO 2 samples.…”

Section: Raman Analysismentioning

confidence: 99%

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

2013

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Abstract:This work reports the study concerning the structure and magnetic properties of undoped CeO2 and Fe-doped CeO2 (Ce1−xFexO2, 0.01 ≤ x ≤ 0.07) nanospheres with diameters of 100∼200 nm prepared by hydrothermal method using polyvinylpyrrolidone (PVP) as surfactant. The prepared samples were studied by using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray absorption near-edge structure (XANES), and vibrating sample magnetometry (VSM). The XRD results showed that Fe-doped CeO2 was single-phased with a cubic structure, and with Fe 3+ successfully substituting in Ce 4+ sites. Raman spectra showed a redshift of F2g mode that caused by the Fe doping. The samples of both undoped CeO2 and Fe-doped CeO2 exhibited room temperature ferromagnetism, and the saturated magnetization (Ms) increased with increasing Fe content until x = 0.05, and then the samples displayed ferromagnetic loops as well as paramagnetic behavior. The roles of Ce 3+ and Fe 3+ spin electrons are discussed for the ferromagnetism in the Fe-doped CeO2.

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Section: Raman Analysismentioning

confidence: 99%

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

2013

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“…37 Since the Ce-8O vibrational unit is very sensitive to any disorder in the oxygen sublattice, the Raman line observed is a direct measure of the sublattice quality. 32,[38][39][40] FIG. 5.…”

Section: Raman Spectramentioning

confidence: 99%

Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

et al. 2015

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In the present study, monodispersed CeO2 nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.

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“…Bulk thermodynamic data may be suited to understand trends but are likely of very limited value for these nanocrystalline, ultrathin films, as shown in recent investigations of nanocrystalline ceria films [44,45].…”

Section: B) High-k Oxygen Deficiencymentioning

confidence: 99%

Thermodynamic considerations in the stability of binary oxides for alternative gate dielectrics in complementary metal–oxide–semiconductors

Stemmer¹

2004

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

108

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A number of binary oxides have been predicted to be thermodynamically stable in contact with Si and are candidates to replace SiO 2 in CMOS. However, reactions leading to the formation of interfacial silicide, silicate or SiO 2 layers have been reported when these oxides are exposed to high temperatures during device processing. Different pathways have been proposed in the literature to explain these reactions. In this paper, a thermodynamic analysis of the proposed reactions is performed. The analysis includes gaseous species, because typical gate dielectrics are ultra-thin layers and diffusivities for species from the surrounding atmosphere, such as oxygen, may be high. Furthermore, nonstoichiometry of the high-k oxide, as may be resulting from nonequilibrium deposition processes or reducing atmospheres during processing is also considered. Studies are proposed to distinguish between possible reaction mechanisms. Finally guidelines for stable interfaces are presented.3

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Raman Spectroscopy of Nanocrystalline Ceria and Zirconia Thin Films

Cited by 187 publications

References 19 publications

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

Thermodynamic considerations in the stability of binary oxides for alternative gate dielectrics in complementary metal–oxide–semiconductors

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