Optical functions of uniaxial ZnO determined by generalized ellipsometry

Jellison, G. E.; Boatner, L. A.

doi:10.1103/physrevb.58.3586

Cited by 219 publications

(123 citation statements)

References 20 publications

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“…The drop in the QY near the band edge energy was not as sharp as expected for a direct band semiconductor due to the ±5 nm bandwidth of the monochromator. The feature observed immediately before this drop is an effect of the exciton absorption just below the band edge [20]. The height of the QY curve decreases as the carrier concentration increases.…”

Section: Photocurrent Quantummentioning

confidence: 93%

“…Figure 12 shows the penetration depth of light δ for ordinary polarization (δ = 1/α, where α is the optical absorption coefficient) in ZnO as a function of the wavelength in the UV region [20]. Since all of the crystals were oriented with the c-axis perpendicular to the surface, the ordinary optical functions are used.…”

Section: Optical Measurements and Quantum Yieldmentioning

confidence: 99%

“…The ellipsometry data (upper curve from 250 to 400 nm) was replotted from [20] for use in this figure, since doping does not appreciably affect the optical properties above the band edge. However, the transmission data (lower part of the curve between 400 and 800 nm) was found to change significantly as a function of the carrier concentration.…”

Section: Optical Measurements and Quantum Yieldmentioning

confidence: 99%

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Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

Paulauskas

Jellison

Boatner

et al. 2011

International Journal of Electrochemistry

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The photoelectrochemical stability and surface-alteration characteristics of doped and undoped n-type ZnO single-crystal photoanode electrodes were investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak depended on time and the NaOH concentration in the electrolyte, but were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with the significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. ZnO doping methods were found to be effective in increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.

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Section: Photocurrent Quantummentioning

confidence: 93%

Section: Optical Measurements and Quantum Yieldmentioning

confidence: 99%

Section: Optical Measurements and Quantum Yieldmentioning

confidence: 99%

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Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

Paulauskas

Jellison

Boatner

et al. 2011

International Journal of Electrochemistry

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“…It has been shown by numerous authors, that the measurement of the optical properties of ZnO allows the indirect determination of its electrical properties [2,3,4] when the used spectral range includes the photon energies around the band gap. There are many approaches in the literature for the parameterization of the dielectric function of ZnO [5] in the gap region, including Adachi's model dielectric function [6], Holden model [7,8], Elliott's formula [9], the Tauc-Lorentz (TL) model [10,11] sometimes combined with a Drude oscillator for the IR part [3], model based on dispersion theories [12] or using a quadratic fit to the absorption edge [13]. There are other promising models like the Herzinger-Johs generalized critical point model [14] or the b-spline model by Johs and Hale [15] which can be useful to describe the dielectric function of ZnO.…”

Section: Introductionmentioning

confidence: 99%

Approaches to calculate the dielectric function of ZnO around the band gap

et al. 2014

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Being one of the most sensitive methods for optical thin film metrology ellipsometry is widely used for the characterization of zinc oxide(ZnO), a key material for optoelectronics, photovoltaics, printable electronics and in a range of critical applications. The dielectric function of ZnO has a special feature around the band gap dominated by a relatively sharp absorption feature and an excitonic peak. In this work we summarize and compare direct (point-bypoint) and parametric approaches for the description of the dielectric function. We also investigate how the choice of the wavelength range influences the result, the fit quality and the sensitivity. Results on ZnO layers prepared by sputtering are presented.

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“…In current generalized ellipsometers for characterizing anisotropic systems, however, either additional variables [1], e.g., the angle of incidence and the azimuth angles of the polarizer (or analyzer) and of the sample, are changed, or components not commonly found in a conventional rotating element ellipsometer are needed [2,3]. Even in the simplest case ofuniaxial materials, two variables, i.e., the azimuth angles of the polarizer and analyzer, are required if sets of T and A are measured to determine the dielectric tensors of the materials [4].…”

Section: Introductionmentioning

confidence: 99%

Generalized Ellipsometry Using a Rotating Sample

Wood

Golding

2001

MRS Proc.

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We propose a generalized ellipsometric technique using a rotating sample. The ellipsometer consists of a polarizer, a rotatable sample holder, an analyzer, and a detector. Fourier coefficients are measured and used to extract the system's dielectric tensors and film thicknesses. The main advantage of the technique is that all parts of the ellipsometer are fixed except the sample, whose azimuth angle can be modulated. We show calculated responses to isotropic and anisotropic materials as well as superlattices. Potential applications for characterizations of anisotropic nanostructures are discussed.

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Optical functions of uniaxial ZnO determined by generalized ellipsometry

Cited by 219 publications

References 20 publications

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

Approaches to calculate the dielectric function of ZnO around the band gap

Generalized Ellipsometry Using a Rotating Sample

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