An ellipsometric investigation of the anodic oxide of molybdenum

Smet, D. J. De

doi:10.1016/0013-4686(76)85170-5

Cited by 17 publications

(16 citation statements)

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“…Moreover, this annealing treatment also causes extensively deeper electron trapping at oxygen vacancies. [29][30][31] Nonetheless, it is clear from the x-ray photoelectron spectroscopy (XPS) 22,24 and also from the reported optical studies that even after undergoing different annealing cycles over the reported temperature range, lithium-molybdenum bronzes are still found to be microcrystalline in nature.…”

Section: Experimental Preparation Of LI X Moo 3 -Bronze Thin Filmsmentioning

confidence: 96%

“…Optical and Electrochromic Properties of Annealed Lithium-Molybdenum-Bronze Thin Films 625 where (30) is a measure of the structural disorder normalized to <V 2 > o , the zero-point uncertainty in the atomic positions. The values of o were calculated using the relation 88-90 (31) where denotes the Urbach slope, o is a temperature-independent but material-dependent parameter and mostly is of order unity, and h ph is a characteristic phonon energy associated with Urbach tail.…”

Section: Urbach-tail Bandwidth E E and The Oscillator Modelmentioning

confidence: 99%

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Optical and electrochromic properties of annealed lithium-molybdenum-bronze thin films

Hussain

2002

Journal of Elec Materi

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Optical band gaps, Urbach inverse slopes, and coloration bands of various samples of annealed, microcrystalline Li x MoO 3 -bronze thin films in the concentration range 0 Ͻ x Ͻ 0.6 were determined over the photon energy range from 0.4 eV to 4.2 eV. On investigation, it is learned that the measured, optical band gaps do not shift rigidly over the annealing temperature range 293 Յ T Յ 423 K and, therefore, do not reveal the Burstein-Moss effect or reflect any stable, crystallographic phase transformation during any investigated annealing cycle. A model relating the temperature-dependent optical gap to the real part of the refractive index has also been developed, and this model fits very well to the annealed data within a maximum error of about 20%. Next, using an oscillator model, a phonon energy of ϳ0.08 eV was obtained, which is very close to the characteristic phonon energy of the material, MoO 3 . Using this model, it becomes more certain that the contributions to the Urbach absorption edge for the annealed-molybdenum bronzes are coming from the structural and compositional disorder. In another finding, it was found that the absorption-peak energy for the annealed data was about 1.5-1.6 eV, which is still broad and asymmetrical, and therefore, it is almost of the Mo 6ϩ (or Mo 4ϩ )-Mo 5ϩ intervalence or polaronic type. Using the polaron model, the half-bandwidth of the coloration bands of investigated, annealed Li x MoO 3 -thin films was found to be almost constant, which is consistent with the nonrigid band behavior.

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Section: Experimental Preparation Of LI X Moo 3 -Bronze Thin Filmsmentioning

confidence: 96%

Section: Urbach-tail Bandwidth E E and The Oscillator Modelmentioning

confidence: 99%

Optical and electrochromic properties of annealed lithium-molybdenum-bronze thin films

Hussain

2002

Journal of Elec Materi

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“…This was Paper 79 presented at the New Orleans, Louisiana, Meeting of the Society, Oct. [7][8][9][10][11][12] 1984.…”

Section: Acknowledgmentmentioning

confidence: 99%

“…Manuscript submitted Oct. 29, 1984; revised manuscript received Jan. 9, 1985. This was Paper 79 presented at the New Orleans, Louisiana, Meeting of the Society, Oct. [7][8][9][10][11][12] 1984.…”

Section: Acknowledgmentmentioning

confidence: 99%

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An Optical Study of the Deposition, Discharge, and Recharge of Manganese Dioxide Films

Ord

Huang

1985

J. Electrochem. Soc.

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The galvanostatic electrodeposition of manganese dioxide films onto a platinum substrate is studied over a thickness range from 0 to 2000 nm. At the upper end of the thickness range, optical absorption causes the ellipsometer null settings to approach within 0.02 ~ of the infinite thickness limit, at which the films are indistinguishable from sub. strates. The optical extinction coefficient increases with film thickness over the range 0-50 nm, but from 50 to 160 nm the films have optical constants which are independent of thickness but which depend on the deposition current density. Beyond 160 rim, the optical data become progressively more difficult to interpret in terms of uniform isotropic or anisotropic film models. When relatively thin films (50 nm) are transferred to alkaline electrolyte and are cycled galvanostatical]y, optical changes are observed which correlate well with the electrochemical behavior for both reversible partial discharge cycles and irreversible complete discharge cycles.In a previous ellipsometric study (1), Spricis et al. found the optical properties of manganese dioxide films to be quite sensitive to the deposition conditions. The deposition was carried out using a sequence of potentiostatic pulses which enabled the process to be studied using a conventional ellipsometer, and increases in deposition potential and pulse duration were both reported to lower the extinction coefficient of the film by as much as a factor of two. For thicknesses below 40 nm, both the refractive index and the extinction coefficient were reported to vary somewhat with film thickness, and above about 70 nm the optical data were found to deviate from the theoretical curves. The thickness dependences were attributed to insular structure in the thinner films and surface roughening in the thicker films, and the extinction coefficient variation was attributed at least partially to a change in porosity.In this paper, we use an automated ellipsometer to follow the galvanostatic deposition and charge-discharge cycling of manganese dioxide films. We study deposition over a current density range of 64 for thicknesses up to 2000 nm to see whether the reported dependence on thickness and deposition rate is found also under galvanostatic conditions. In the optical analysis, we use both isotropic and anisotropic film models to see whether or not the dependence of refractive index on film thickness is an artifact resulting from isotropic analysis of an anisotropic system. The objective of the study of charge-discharge cycles in alkaline electrolyte is more to evaluate the usefulness of ellipsometry for such measurements than to provide any definitive statement about the processes involved. Ellipsometry is an effective tool for the study of homogeneous film-conversion processes, but heterogeneous processes can only be studied if the film remains stratified.This investigation forms part of our continuing study of oxidation and reduction processes which involve ionic transport through thin solid films. Included in this ...

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ChemInform Abstract: AN ELLIPSOMETRIC INVESTIGATION OF THE ANODIC OXIDE OF MOLYBDENUM

Smet¹

1977

Chemischer Informationsdienst

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An ellipsometric investigation of the anodic oxide of molybdenum

Cited by 17 publications

References 10 publications

Optical and electrochromic properties of annealed lithium-molybdenum-bronze thin films

Optical and electrochromic properties of annealed lithium-molybdenum-bronze thin films

An Optical Study of the Deposition, Discharge, and Recharge of Manganese Dioxide Films

ChemInform Abstract: AN ELLIPSOMETRIC INVESTIGATION OF THE ANODIC OXIDE OF MOLYBDENUM

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